CA2070707C - Heating and cooling system for a building - Google Patents

Abstract

A reversible vapour compression refrigeration plant serves as an air conditioner for cooling or as a heat pump for heating. A main stream of inlet air is divided into separate main and bypass streams of air and proportion of flow between the two streams is varied in an inverse ratio so that as flow through the bypass duct increases, flow through the main duct decreases and vice versa. When the plant is used for heating, the main stream is heated by a supply heat exchanger acting as a condenser and when the plant is used as an air conditioner, the supply heat exchanger acts as an evaporator. Also, as an additional alternative, as a desired air space temperature is approached, preferably heat rejected by a condenser in the heating mode, or heat gathered by the evaporator in the cooling mode, as gradually reduced by reducing refrigerant flow therethrough by modulating compressor suction. Full fresh air or full re-circulating air modes, or a combination of mixed and re-circulating air can be used.
Also, energy is saved in both the heating and cooling modes by locating an exhaust heat exchanger within exhaust flow discharged from the space to be heated or cooled.

Description

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Ip the invention relates to a heating and cooling system for air, for example ~or ~ttaint~ining a desired air ~.emperature in a building using fresh air or re-~i~~ulating room air or a mixture thereof, by using an air-~conda.ti~~ing System which can be °'reversedls to function as a he~.t pump.
It is known that a conventional refrigeration system using a vapour compression x°efrigerator can be reversed to function as a heat pump,. A conventional r~frigerati.on plant cools a sp~ae by extradting heat 20 therefrom by evapora~Cion of a refrigerant or working flhid, and rejects the heat outsade by condensation. Onthe other hand, a heat pump utilizes the heat reaected by condensation ~f the refrigerant to heat a space, and extracts heat from outside by evapmration of the 2~ refrigerant.
A refrigeration or heat pump plant is said to be in thermal balance ~rheaa rats of evaporation aid condensation are equal: This required ~.atohing the 30 capacity of the evaporator and condenser as closely as possible, and this matching can present problems. l~atchix~g or balancing ho'oapacity of a vapour compression system is particularly difficult if that s~rstem is to be reversed tai be ~xsed as a heat pump as well as ,gin air conditioner. Air 35 conditioners are generally matched to ~0 per cent to 95 per cent of the maximum cooling load so as not to run continuously for the majority of the cooling season because they are oversized when the weather is moderate. An ~Q~~~~~
_2_ over-sized air conditioner tends to cycle off, that is to switch off, having achieved the space temperature requirements before sufficient de-humidification is accomplished. This results in cool but muggy air within the air conditioned space because the evaporator generally operates below the dew point temperature of the air being treated.
Tn air-conditioning systems, most of the matching problems arise from the wide variations that can be ' e~perienaed by the condenser when it is located in ambient air outside the building. Many methods of bringing into balance the rates of evaporation and condensation are available for air--conditioners as will be described. On the other hand, while heat pumps are well known for their relatively high cycle efficiency, problems have arisen in matching the heat rejection capacity of the condenser with the heat absorbing capacity of the evaporator. Tf the range of outside air temperature passing through the condenser is relatively narrow, matching of the evaporator and condenser capacities i.s relatively easy and the heat pump can function efficiently. However, if_there is a relatively wide range of tem~Zerature differences across the condenser of the heat pump, matching of the condenser and evaporator capacities while maintaining high efficiency and high discharge temperature becomes very difficult.
Matching of the capacities of the evaporator and condenser in a refrigerating unit has been accomplished by many different approaches. For a proper balance, refrigerant pressure within the system must be controlled accurately, and this can be done by controlling the rates of condensation and evaporation, using many different methodsa One means of approaching balance for common, commercially produced air-conditioners when used in a temperate climate where less condenser capacity is required is to partially flood the condenser with liquid refrigerant, thus effectively reducing condenser area to compensate for cooler ambient air. This required using larger amounts of refrigerant than would otherwise be required. On the other hand, when attempting to match capacities of the condenser and evaporator in a heat pump system when temperature of air entering the candenser varies, as in fresh air heating, many other difficulties can arise. Typical problems encountered include attempting to maintain design condensing pressure for all outside temperatures with a constant volume make-up air passing through the condenser coil. If the heat pump system has only a single eornpressor, unloaders using a bypass regulator are required to short circuit refrigerant, thus reducing heat capacity demands but this approach reduces efficiency when attempting to maintain adequate pressure in the condenser.
One factor in compressor matching relates to the density of the vapour to be compressed. Any increase in specific density of the vapour to be compressed requires a corresponding increase in compressor power which is not easily attainable with most single speed ~ampressors.
While some compressors are tw~-speed types,. such types require separate windings for each speed, which increases in control complexity, and thus two speed compressors are not common. Running a compressor at low speed to reduce compressor output often increases refrigerant density, which requires a correspondingly higher power input per stroke. F~ynamic balancing becomes more difficult at low speed, and oil entrainment for compressor lubrication can suffer at low speed. While in general improved lubrication takes place with high speed compressor operation, adequate return of the oil to the compressor is necessary. Varying operating speed of a compressor can result in poor lubrication and correspondingly aggravate wear of the compressor.
When a heat pump or air conditioner cannot reject all the heat gathered, compressor discharge pressure (i.e.

a -condenser inlet pressurey increases as the vapour occupies a higher specific volume in the condenser than as a condensed liquid. If pressure limiting controls are present, the compressor will shut off until the discharge pressure drops below some nominal reset value. Automatic reset can cause short-cycling of the compressor which pumps oil from the compressor and could result in premature failure due to insufficient lubrication. Alternatively, manual reset of the compressor can be used but this is inconvenient, but it can overcome the short-cycling problems described above.
Constant volume air-conditioners using make-up air have to accommodate wide variations of ambient temperature and still provide a desired cooled space temperature. Clearly, as the ambient temperature rises, mare heat must be removed from the air entering the evaporator than with lover ambient temperatures. In order to accommodate these outside air temperature variations in an air conditioner, air flow control means are provided to regulate flow of outside air through the condenser coil of the air-conditioner. The higher the ambient temperature, the more air must pass through the condenser coil and vice versa> Usually air flow control means, termed face dampers, are fitted to control air flow through the main condenser coil. For relatively cool ambient temperatures, where not much head is removed from incoming air, the face dampers will be closed so that little of the outside air will pass through the condenser. As ambient or outside temperature rises, the face dampers will be opened, to ensure that more outside air will be passed through the condenser.
Many prior art heat pumps have provisions of introducing a limited amount of fresh air into the building stream, and separate exhaust fans expel a similar quantity of exhaust air. As the public's awareness of insufficient fresh air supply to buildings increases, new demands are _5_ placed upon heat pumps, air conditioners and, other equipment to use greater volumes of fresh air. It is well known that exhausted air contains heat, and while attempts have been made to collect heat from the exhausted air using conventional heat exchangers, such devices are costly, power consuming and relatively inefficient for heat transfer to incoming air.
In all air-cond~tionin~ systems known to the inventor, the condenser used to reject heat is located in ambient air, and, to improve heat transfer, the condenser can be cooled by many different methods. The efficiency of heat transfer from the hot refrigerant in the condenser to ambient air is dependent, among other things, on temperature difference between the hot refrigerant and the ambient air. Various means, such as sprayed water cooling for direct evaporation on the coil have been used 'to assist in condensing the refrigerant.
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The invention reduces the difficulties and disadvantages of the prior art by providing a relatively low capital cost hewing and cooling system which also operates efficiently in both heating and cooling modes.
The invention also provides a relatively simple means of reducing differences 'in matching heat transfer capacity between the evaporator and condenser of a heat pump, 'by controlling essentially constant volume fresh air flow therethrough automats.cally to maintain high efficiency for a relatively wide range of outside temperature. Also, by varying compressor suction in response to set point variation, evaporator temperature is controlled, which in turn controls heat rejection at a condenser.
Also, the efficiency of heat transfer relative to a coil is improved by locating the coil actually in exhaust air flow from a building being cooled or heated, as opposed _5_ to locating the cail in ambient air which requ~.res an auxiliary fan or other means to effect heat transfer. In air-conditioning, because air exhausted from the building being cooled is usually cooler than ambient, a cooler condensing medium for the condenser is attained which, by itself, improves heat rejection in the condenser. On the other hand, in the heat pump mode, because air exhausted from the building being heated is usually warmer than winter outside air, locating the evaporator in exhaust air flow from the building being heated will recover more heat in the evaporator than the prior art location of the evaporator in outside air. This additional heat extracted from the exhaust air can then be "intensified'° by the compressor before beza~g rejected into the fresh air stream by the condenser.
1 method according to the invention is for treating air and comprises the steps:
generating main and bypass streams of air, and initially maintaining the two streams of air separate from each other, directing the main stream of air through a supply heat exchanger of a vapour compression machine to change temperature of the main stream of air, generating a first control signal representing a difference between an actual first reference temperature and a pre-determined first reference temperature, and then controlling ratio of flow of the main and bypass streams of air in response to the first control signal so that if the first contral signal reflects an actual first reference temperature below the pre-detexznined first reference temperature, the main flow is decreased if heating the main flow, or increased if cooling the main flow, and if the first signal reflects an actual first reference temperature above the pre-determined first reference temperature, the main flow is increased if heating the main flow, or decreased if cooling the main flew, and then mixing the main stream of air after passing through the heat exchanger with the bypass stream of air, if any air were passed through the bypass flow control means, prior to delivering the mixture of air streams.
Preferably, the main stream of air i~ controlled also in response to tkae first dontrol signal' in an inverse flow ratio to tie bypass stream of air so that as flow through the main duct increases, flour through the bypass duct decreases and vice ~e~sa.
The method also includes generating a second control signal reflecting difference between an actual second reference temperature and a pre-determined second reference temperature. The method fuxther comprises gradually varying flow of refrigerant to a compressor of the vapour compression machine in px'oporta.on t~ diffex~nc~
between the aetual second reference temperature and the pre-determined second reference temperature. Th~.s control can be attained by controlling heat gathered in an evaporator of the vapour compression machine.
An apparatus according to the invention is for treating air in a space and comprises a supply chamber, propulsion xi~eans, a supply heat exchanger, a (first temperature sensor means, a air flow control means, an actuator means and mixing means: The chamber has main and bypass ducts for receiving and initially maintaining separate main and bypass streams of air. The propuls~.on means is for generating air flow through at least one of 3~ the ducts: The supply heat exchanger is of a vapour compression machine and i~s provided in the main duct to change temperature of the main stream of air passing through the main duct. The first temperature sensor means _g_ generates a first control signal representing difference between an actual first reference temperature and a predetermined first reference temperature. The air flow control means controls flow of air through the main and bypass duds. The actuator means is responsive to the first control signal arid is operatively coupled to the bypass flow control means to actuate the control means so as to vary ratio of restriction to air f low through the main and bypass ducts, the actuator means being responsive to the first aowtrol signal. The mixing means is for ' mixing together the streams of air discharged from the main and bypass ducts prior to discharging the mixed streams of air into the space.
Preferably, the air flow control means comprises a main flow control means arid bypass flow control means cooperating with the main duct and bypass duct respectively to control flow therethrough and the apparatus further comprises couplihg means coupled to the main flow control means and the bypass flow control means so that the main flow control means is actuated in an inverse relationship to the bypass flow control means. _ The apparatus further comprises a second temperature sensor means and a heat exchange control means.
The second sensor means generates a second control signal representing differex~ae between an actual second reference temperature and a pre-determined second reference temperature. The heat exchange control means cooperates with a compressor of the vapour compression machine so that heat exchange is in proportion to difference between the actual second reference temperature and the pre-determined second reference temperature. zn this way, as the said difference becomes gradually smaller, heat transferred between air passing through the supply heat exchanger is gradually reduced, and vice versa. Preferably, the heat exchange control means is a fluid flow modulating valve cooperating with a conduit communicating with an inta3ce of the compressor of the vapour compression.
Another method of treating air according to the invention comprises the steps of:

(a) directing a stream of air through a supply heat exchanger of a vapour compression machine to change temperature of the stream of air, (b) generating a second control signal representing the difference between an actual second reference temperature and a pre-determined sedond reference temperature, 25 and (c) controlling heat 'transfer a~t the supply heat exchanger in proportion to difference between the actual second reference 20 temperature end the pre-determined second reference temperature. The controlling of the heat exchange at the supply heat exchanger is preferably by contrr~lling heat gathered in an evaporator of the machine by 25 controlling a pressure difference between an intake oil a compressor and the evaparator.
Another apparatus for treating air comprises a sup~aly chamber, a supply heat exchanger, a temperature 30 sensor and a heat exchange control means. The supply' chamber has a duct to receive air to be treated and a propulsion means for generating flow of a stream o~ air through the duct. The supply heat exchanger is of a vapour compression machine and is provid~:d in the duct to chamge 35 temperature o~ the stream of air passing along the duct.
The temperature sensor c~~nerat~s a second control signal representing difference between an actual second reference temperature and a preedetermined second reference 2~~~~~"~

temperature. The heat exchange control means controls heat exchanged at the supply heat exchanger, so that 'the said heat exchange is in proportion to difference between the actual second reference temperature and the pre-determined second reference temperature. The heat exchange control means cooperates with an intake of a compressor of the vapour compression machine so that as said difference in temperatures become, smaller, heat exchanged to the air passing through the heat exchanger is gradually reduced, and vice versa.
Yet another method of heating an air space according to the invention comprises the steps of.e drawing air through a condenser of a heat pump so that condensation of refrigerant therein heats the air prior to discharging the air into the air space, drawing aix from the space to be heated through an evaporator of the heat pump to heat the refrigerant therein, transferring the heated refrigerant from the evaporator to the condenser.
Yet another apparatus according to the invention is for heating an air space and comprises an inlet duct and an outlet duct communicating with the space, and means to move the air through the inlet duct into the space, and to discharge air from the space through the outlet duct. The apparatus also includes a refrigerant condenser in the inlet duct, a refrigerant evaporator in the outlet duct, and refrigerant conduit means and a compressor communicating the evaporator and the condenser and transmitting refrigerant therebetween to function as a heat pump.

Yet a further method according to the invention is for cooling an air space and comprises the steps af:
drawing air through an evaporator of a refrigeration plant sa that evaporation of the refrigerant thereof cools the air prior to discharging the aa:r into the space, drawing air from the space to be cooled through a condenser of the refrigeration plant to cool the refrigerant thereof, transferring the cooled refrigerant from the condenser to the evaporator.
Yet a further apparatus, according to the invention, is for cooling an air space and comprises an inlet duct and an outlet duct Gommunicatinc~ with the space, and means to move the air 'through the inlet duct into the space and to discharge air frbm the space through the ~utlet duct. The app~ra~us gu.rther includes a refrigerant evaporator i.n the inlet duct; a refrigerant condenser- in the outlet duct and ~e~frigerant conduit means and a compressor communicating th.e evaporator and condenser and transmitting refrigerant therebetween to function as a refrigeration plant:
A detailed disclosure following, related to drawings, describes several apparatuses and methods according to the invention which are capable of e~tpressior~
in structure and methods ether than those particularly described and illustrated.
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Figure 1 is a simplified fhzid schematic showing a refrigerant circuit of a heating and cooling P
_~.2_ system according to the invention, also showing some p~riph~ral control circuits, temperature sensors and schematic connections;
Figure 2 is a simplified d~.agram of an air flow circuit of the apparatus accarding to the invention, the apparatus being s3~own in a one hundxed percent fresh-air mode;
Figure is a ,simplif~.ed diagram ~~ the air flow circuit of the apparatus according to the invention, the apparatus being sla~wn in full outline in a one hundred percent re-circulating mode, and in broxeh outline i.n a mixed fresh/re9circulating air mode;

Figure 4 is a simplified top plan as seen from lines ~-~4 of Figures 5 and 6, shown partially in section, of a coupled system embodiment according to the 2p invention showing relative Iocati.on of various .

other coanponents being omitted components, many fox clarity; -Figure 5 is a simplified elevation and section of the apparatus as seen from line 5-5 of Figure 4, some potions beang omatted for clarity, the invention being shown in the one hundred percent re-circulating mode;

Figure is a simplified elevatioa~ of the a~aparatus 6 as seen from lines 6-6 of Figures 4 and 5, dome portions being omitted for clarity;

Figure 7 is a simplified lAnc~itudinal section through a coupling device according to the apparatus, the device being shown in an oxtended or uncoupled configuration;

Figure 8 is a simplified section on line 8-8 of Figure 7;
Figures 9, and il are simplified diagrams showing actuation of 5 the coupling device and dampers;
Figure 12 is a simplified electrical schematic showing a portion of electrical control jeans, and some mechanical components which are 10 actuated electrically, some significant signals and some connections to other components are also shown.
DETAILED DT~~~oBiTfftE
Fiqure 1 A heating and cooling apparatus 1~ according to the invention resembles an air-conditioning system for cooling air, and can also be rew~rsed to function as a heat pump to heat the air. 'fhe .terms "vapour compression machine°' , "heat pump" , "refrigeration plant°° or "air-conditioner" as used herein are used synonymously to describe a vapour compression machine which can be operated in either mode, td deliver heat to or to extract heat from a main air spaoe e.g. a room within a building. The apparatus 1~ has a motor/compressor assembly 1.2 complete with an internal line-break overl~aad device, crankcase heater and o~ther:features which are not shown but are common to refrigeration plant compressors. The apparatus includes generally similar heat' exchange coils 15 and lf, .
the coil 15 being for exhaust air which is returned to outside, and the coil i~b being for supply air drawn into the building from outside.. Each coil is relatively conventional for heat pump, and is fabricated from copper or aluminum tubes with fins, with a distributor and a header and circuited so that one-half of the coil is counterflow regardless of direction of refrigerant flow.

-3.4-each heat exchange coil is fitted within a refrigerant circuit with components as follows, most of which are also found in conventional refrigeration plants or air-conditioning systems. The coils 15 and t~ can also be referred to as exhaust and supply heat exchangers respectively.
Direction of flow in the refrigerant circuit of Figure 1 is designated by three different types of arrows.
A large or mufti-bodied air~w ~h~w~:direction of flow which is independent of the mode of~ operation; in other words the direction of refrigerant flow in conduits designated by a mufti-bodied arrow does not change as the mode of operation changes. A second type of ar~cow is a single-bodied full outline arrow which shows direction of refrigerant flow in a heating mode only. A third type of arrow is shown in broken outline, shows a reversed direction of refrigerant flow which occurs only in a cooling mode. Flow in the heating mode is described first, and thus refers to flee arrows in full outline; namely the mufti-bodied arrows and the single-bodied full outline arrows. Most of the refrigerant flow in the cooling mode follows conventional air-conditioning practice, and is described briefly later.
In the heating mode, the exhaust coil ~.5 acts as an evaporator, and thus receives liquid at an inlet thereof, and exhausts vapour at an outlet thereof.
Conversely, the supply coil ~.6 acts as a condenser and receives vapour at an inlet~thereof and exhausts liquid at an outlet. A first liquid line ~.~ feeds liquid into the exhaust air coil ~.5 and a vapour line 21 leaves the coil.
An exhaust coil thermostatic expansion valve 23 is fitted in the line Z~ and an exhaust coil check valve 25 is coupled in parallel with the valve 23. The valve 2~ is connected by a capillary tube 2~ to a 'temperature sensing bulb ~6 on the line 2~, at the outlet of the coil 15, the valve 23 thus being responsive to the coil outlet temperature. A second liquid fins 27 extends from a 2~"~~~~~
-i5-junction 24 with the first liquid line ~9 and feeds liquid to a de-superheating thermostatic expansion valve 28, and then feeds liquid into a pressure vessel 30 with an internal 3-tube 32 on an outlet connection.
The vapour'line 2~ feeds vapour into a hermetic, pilot slide-type, two-position, four-way reversing valve 3~
which is actuated by an integral solenoid controlled by signal to be described. The valve 3~ communicates with three other lines, namely a refrigerant suction line 36, a refrigerant vapour line 38 and a discharge line ~~
extending from the putlet of the compressor: Tn the heating mode as shown, the valve 3~ is positioned so that the vapour line 2l communicates with the refrigerant suction line 3~~, and the discharge line ~~ communicates with: the vapour line 38. The line 36 communicates with a modulating suction cut-off valve 37 which is electronically controlled by means . ~o be described, and, when required, can throttle refrigerant as it pisses along the line 3~i towards the compressor l2. One example of the valve 37 is manufactured by the Sporlan Valve Compaa~y of St. Louis, tulissouri, U.S.A., and is called a CDA- electronic temperature control valve and is a solenoid-actuated, flow modulating valve. This is an important valve for the invention and, when required, , can throttle supply of the vapour to the compressor to provide significant advantages in heating and cooling, as will be described, from full flow to a small fraction of normal flow., The 3-tubo 32 in the pressure vessel 3~
communicates with a suction line 42 which feeds vapour into the compressor 12 and communicates with the discharge line ~0: A temperature sensing bulb .~~ on the line ~0 controls the thermostatic expansion valve 28 through a capillary tube .45. The valve 28 limits compressor discharge temperature by metering liquid refrigerant directly into the final com~aressor suction line 42.

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-3:6-The refrigerant vapour line 38 feeds vapour into the coil 3.6 for heating the supply air by condensation.
The soil ~.~ communicates with a thermostatic expansion valve ~6 mounted in parallel with a supply coil check valve.
d8. A temperature sensing bulb ~4T in the line 3a controls the valve .~6 through a capillary tube ~9. A temperature sensor 51 is fitted in an outlet line 50 extending from the coil 15 to the junction ~~ with the liquid line ~.9. The sensor 51 is connected by a tube or lead 52 to a remote ~.0 sensing proportioning controller 53 which positions a modulating actuator 55 through a lead 5~.
The sensor 5a is located on a side of the supply coil 1.6 which serves as an outlet side when the system operates in the heat pump made, and this sensor generates an actual first reference temperature signal 65. The signal b5 reflects actual refrigerant condensing temperature and is fed into the controller 53 which is pre-programmed with specific parameters. Hereinafter and in the claims, the 2o actual temperature of the condensing refrigerant circulating within the circuit. is referred to as the 'actual first reference temperature'°, and the term "pre-determined first reference temperature" refers to one of the known parameters programmed into the controller 53.
The controller, in turn, generates a first control signal 56 wY~.ich is outputted through a damper relay bob as a damper relay output signal fl to the actuator 55. The relay ~6 is for inverting the signal 56 in the cooling mode as will Dae described. The control signal 55 represents a difference between the actual first reference temperature 55 and the predetermined first reference temperature as pre-programmed in the controller 53 and is important to the invention as will be described, particularly with reference to Figure 1.2. The proportioning controller 53 is an ambient compensated dev~.ce, such as a Honeywell T 9~1A 106. or T 775 series, having an output range from O to 135 ohms.
The modulating actuator 55 has a rotating arm 2~~~~~

output complete with an adjustable stro3ce and adjustable dead band response. The actuator 55 is directly mechanically coupled to face dampers 6~ to control flow of air therethrough by positioning the dampers in any position between and including closed and open positions. The face dampers ~2 are selectively coupled through a telescopic coupling means 5? to bypass dampers 5~ in the fresh air mode, but can be ~decoupled 'as will be described. The dampers 5~ are generally similar to the face dampers 5~
but, when decoupled from the coupling means 5?, are normally gravity-biased to a closed position and are an important feature of the invention. Both dampers 58 and f3 are parallel blade type and serve as variable air flow control means and determine flow through the supply coil as 3.5 will be described. The actuator 55 can be a Honeywell M
984 which is electrically coupled by a lead 5~ to a temperature control system ~O which is described with reference to Figure l~ . The system 60 is connected by a lead 53 to a motor 6~! controlling the modulating suction cut-off valve 3? as will be described. The motor 64 can position the. valve 37 in any position between fully open and fully closed: The face and bypass dampers 53 and 5~
and associated couplings will be described in m~re detail with reference to Figures 2, 3 and '7-11.
As previously stated, the directions of refrigerant flows as described above relate to operation of the circuit in the heating mode. 6dhen the system is reversed to function as an air-conditioner or refrigeration mode, the reversing valve 34 is actuated so as to couple the line 36 to the line 38, and the line 21 to the line 40.
Clearly, refrigerant vapour passes through the compressor 12, and then passes through the line 25. into the exhaust coil 35, now acting as a condenser, where it leaves as liquid to pass into the junction 24 with the lines ~9 and 2?. From here liquid returns down the line 2? to the valve 28 as before. Liquid also flows from the junction 29 past the sensor 5~. to the expansion valve 45 which meters liquid refrigerant inta the. coil ~6 where it evaporates and gathers heat. The. sensor 5~. is thus at the outlet of the exhaust heat exchanger ~~, now acting as the condenser, and thus senses refrigerant condensing temperature, which is now the actual first reference temperature. The sensor 5~~.
always senses condensing temperature as it is always connected to the outlet side of the condenser, whichever heat exchanger it may be. Vapour passes along the line 38 from the supply coil 16 acting as an evaporator, where it returns through suction lines ~6 and ~~ to the compressor l2. With the exception of the function of the valve 3?, which is to be described, the above desa~iption of flow of the refrigerant througYt the. circuit in the air-conditioning mode is identical to the prior art.
Ficlures 2 and 3 As previously stated, Figures 2 and 3 show air flow through the system and damper positions, with other 2~ components being amatt~d. Figure 2 shows one hundred percent fresh air mode. Figure 3 shows one hundred percent re_circulation air mode in full ~utline, with. an optional mixed fresh/re°circulating air mode configuration in broken outline. Tn all fresh air, re-circulation and mixed air 25 modes, air is moved through a supply chamber 6? of the apparatus 10 under the influence of a supply air fan 68, and through an exhaust chamber 59 by an exhaust air fan ?~.
The fan 68 is located closely adjacent the supply air coil ~~, and draws air therethrough, and the fan ?0 is located closely adjacent theexhaust air coil ~.5 and blows air therethrough. ' (a) Full Freeh Air Mode°I3eating In Figure 2; in the full or one hundred percent fresh air heating mode, the dampers 58 are coupled to the dampers s2 by ~.he coupling means 5? and fresh air is drawn from the outside through a pre-filter ?1 mounted upstream of the face dampers 62. A hora~ontal partition ?3 divides -2g-an inlet air flow path 74 through the chamber 57 into initially separate main and bypass ducts 76 and 'T7 respectively. The main duct includes the face damper 6a, and an inlet space 75 disposed between the face dampers and the supply air coil 16 which is serving as a condenser.
The bypass duct ?f extends from the pre-filter, through a bypass restrictor screen 79 and then through the bypass dampers ~~. The screen ?9 is selected to provide a resistance to air flow approximately equal to the 20 resistance to air flow of the coil ~.6. Thus, when the dampers 5~ and 62 are both half open, volume flow through the ducts 7~ and ?7 is approximately equal.
As previously stated, the telescopic coupling 57 25 couples the bypass dampers 5~ to the face dampers 52 and ultimately to the actuator 55. As will be described with reference to Figures '7-22, the telescopic coupling 57 serves as a means to engage and disengage the coupling between the face dampers 6~ and the bypass dampers 5~.
2~ b9hen the telescopic coupling is engaged as in full fresh air and mixed air modes, the actuator 55 is directly mechanica',ly coupled to both the face and bypass dampers ~2 and 5~ so that the dampers operate an equal and opposite directions to each other. That is, when the face damper 6~
25 is fully open, the bypass damper 5~ is fully closed and vice versa. This is attained by suitable adjustment of linkage lengths and lever angles as will be described with reference to Figures 9-22. Thus, it can be seen that there is an inverse proportionally between the bypass and face ~0 dampers at extremes of movement, and there is a similar inverse proportionality for intermediate positions of the dampers. Because .the dampers 5~ and 6~ are inversely proportionally coupled, as the face dampers 6~ approach the closed position, the bypass dampers 55 open and this 35 decreases flow through the coil its, and increases flow to bypass the coil. This, action occurs in a situation where fresh air temperature decreases, thus requiring a smaller volume flow of colder supply air through the condenser 15.

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_20-Clearly, the colder the outside air, the less volume flow of air is required to maintain optimum balance between the condenser and evaporator. This coupling permits the refrigeration system to be b2ilanced with precision through a range of temperature far wider than in prior art constant volume fresh air systems.
Tt can be seen that the bypass dampers 5~ serve as bypass f low control means cooperating with the bypass duct 7'7 to control flout of the bypass stream of air therethrough. Similarly, it can be seen that the face dampers c2 serve as main flow control means cooperating with the main duct '~6 to control flow of air therethrough.
The dampers 52 and 58 serve as air flow control means for controlling ratib of flow of streams of air through the main and bypass ducts. The fan 6S is located so that an intake thereof receives air from both the coil 1.c6 and the bypass dampers 58, if open. An auxila.ary heater ~Z
receives air from the fan 5~ and can provide additional heat to the spade to be heated with supply sir, as needed.
Auxiliary, heat is needed when there is insufficient capacity in the heat pump alone to meet the fresh air heating demand as is well known in other prior art heat pump systems.
First and second re°circulating dampers ~5 and S6 are disposed between the inlet air flow path '7~ and a return air flow path ~5. The dampers ~S and 55 are also parallel blade type and can be positioned in any position between and including open and closed. The dampers ~5 and 56 in general assume identical positions and are contr~lled concurrently through a variable position damper operating motor 9~. In Figure 2, in the full fresh air mode, the motor ~~ has been actuated by a positioner to be described so that the re-circulation dampers ~5 and 56 are fully closed. Barometric dampers ~2 are fitted upstream of the fan '30 and are responsive to pressure differences thereacross so as to control air flow into the fan 7~, and 2Q'~~~~

thus flow through the coil ~.5 and out to ambient air as exhaust. Heated air from the space passes through the dampers 92 due to suction from the fan 7~, and heat from this air is partially recovered in the exhaust heat exchanger 35, acting as an evaporator. In the prior art, recovery of heat from exhausting inside air is usually costly and inefficient as a separate air-to-air heat exchanger is required. Th~.s,increases installation costs and fan power requirements> If a conventional heat pump is used to gather heat from outside air or other.medium, the outside air is usually a~ a temperature less than the inside air. It follows 'that prior art.heat recovery is less efficient than 3n the present invention, which uses the heated inside air as the heating medium for the evaporator to gather some of this heat which would otherwise be re~Iected. Thus, locating the evaporator in the heated exhaust air stream requires less energy than in the prior art.
In summary; there are five sets of dampers, namely the bypass and face dampers 5~ and 62 which can be ~perated inversely to oath other to divide inlet flow in the fresh air mode, or the damper 58 can be separated as will be described; the re-circulating dampers 85 and 8~
which operate equally together and the .independently operated barometric dampers ~2. 1~s will be described, the re-circulating dampex°s 85 and 86 serve as re-circulating flow control means disposed between the inlet chamber and the main space being heated. The re-circulating flow control means can be set at either apen, closed or at intermediate positions as determined by the mode of operation of the equipment and the amount of fresh air required for the building. The barometric dampers 9~ are also conventional parallel blade type dampers wh~.ch are gravity biased closed and which automatically open to pass air outwardly from the building when the pressure difference across the damper is greatest on the side of the dampers exposed to room air.

(b) Full Re-circulating Air Mode-Heating In Figure 3, referring to the full or one hundred percent re-circulating heating mode shown in full outline, the coupling means 5T has been actuated to decouple the face and bypass dampers ~2 and ~8 respectively, to permit both dampers to claw, as will be described. The motor 90 has been actuated to fully open the first and second re-circulating dampers ~~ and ~6 respectively. The exhaust chamber 69 is now exposed to suction from the supply chamber 67 arid thus, because the pressure differences across the dampers ~2 is essentially zero, the dampers ~2 will automatically close. In the full re-circulating mode, return air from the heated space is now drawn though the second re°circulating dampers ~6 into the inlet space 75, and back through the coil ~6. The fan fib draws the re-circulated air through the coil ~lG to be heated and is then fed back into the space to be heated. The closed dampers 62 and 92 prevent mixing of the two streams of air from the supply chamber ~~ and the exhaust chamber t~. On the opposite side of the dampers 6~ and ~2, fresh air is drawn through 'the ~pem re-circulating dampers Via, through the fan 90 and is then~forced throur~h the coil is back to atmosphere, the fresh air si~nultane~usly being cooled by the coil 15 as the refrigerant boils and extracts heats from outside air as in a conventional heat pump.
(c) Mixed Fresh/Re-circulating Air Mode-Heating In Figure 3, referring to the mixed fresh and re-circulating air anode, the motor 9tt has been actuated by a control to be described to position the first and second re-circulating dampers ~5 and s6 respectively in a partially open position as shown in broken outline. The actual angle of the daanpsrs 85 and ~fi is based on one or more parameters as determined by particular building requirements, e.g. the fresh air requirement of the building, that is, a ratio of fresh to re-circulating air, carbon dioxide levels etc~. ~7sually, depending on outside temperature and operating requirements, for efficient operation of the present invention ratio of fresh air to recirculated air is between about ten and thirty per cent.
To maintain a particular ratio of fresh air to re-circulating air, selective adjustment of the angles of the dampers ~5 and 8~ wduld ba required. aecause of the fresh air requirement, the coupling means 57 is actuated to couple the dampers ~8 and 6~ for inversely proportional movement. The face dampers iR and bypass dampers 5~ have positions which are controlled by the modulating actuator 5~ and the coupling means 5~, and they are essentially independent of the motor ~0. dearly, actuation of the modulating actuator 55 for a mixed fresh air, and re-ciraulating air configuration would not necessarily be identical to that for one hundred percent fresh air or re-circulating -air actuation. With mixed fresh and re-circulating air as described, it is quite common to vary the ratio betwe~ra daytime and nighttime, depending on the usage of the building.
Mixed air operation is as follows. After passing through the pre-filter 7l, a first portion (brokers outline err~w) of the fresh air passes through the inlet air flow path 7~, and a second portion (full outline arrow) of fresh air passes through the re-circulating dampers ~s . The first portion of air passing through the inlet air flow path. 7~ is divided into main and bypass flows by the main and bypass dampers 62 and 58 as previously described, after having been mixed with re-circulating air (full outline arrow) returning through the re-circulating dampers 86 in an amount dependent on the opening of the dampers ~6. The remaining portion (bro~;en outline arrow) of the re-circulating air passes through the barometric dampers 9~
and is mixed with the second portion of fresh air passing through the re-circulating dampers ~5, prior to both portions being mixed in the fan ~0 and passing through the heat exchange coil 15 under the influence of the exhaust fan ~~. Building duct characteristics will determine the actual degree of opening of the dampers ~5 and ~f to attain the desired degree of fresh air and energy savings.
(d) Full Fresh Air Mode--Cooling In a one hundred percent fresh air cooling mode, the telescopic coupling 57 is engaged and the face dampers 62 and the bypass dampers ~8 modulate in inverse proportion to the signal ~~. to .control the main and bypass stream through and around the coil ~,~, nova acting as an evaporator. The re-circulating dampers ~5 and ~6 are closed, and the barbmetric dampers 92 are fully open.
Clearly, the auxilvary heater ~2 is disabled.
Similarly, to the full f~esYa air heating mode, the exhaust air coil receives exhaust air from the space, which, in this mode, is .usually at a temperature cooler than ambient. Consequently, temperature difference for the coil ~5 is greater thannormal, and thus heat trans~er-is improved and "low temperature" that.u~ould normally be lost is partially reclaimed. In conventional air condita:oni:ng, an auxiliary fan usually dx°ives outside air .through the condenser cail, bud by using the exhaust fan 70 to drive cooled room air through the condenser coil ~5, the auxiliary fan which would othercuise normally be required, is eliminated. Z'his is an extra advantage in the present invention. In~summary, less energy is required for the invention as the c~il 15 is operating in a lower temperature, which increases heat transfer and refrigerant sub-cooling, and the auxiliary fan is not needed.
(e) Full Re~-circulating Air Mode-Cooling 3n the one hundred percent or full re-circulating cooling mode, similarly to full re-circulating heating, the re-c~.rculating dampers ~5 and ~6 are both opened and the bypass and face dampers 5~ and 62 are decoupled and the dampers 5S are closed as shown in Figure 3. Similarly, to full fresh air cooling, the coil 3.6 acts as tlae evaporator, and the coil 3.5 as the condenser. Return air from the space room being cooled passes directly through the re-circulating dampers 85 and the supply coil g6 and back into the space to be cooled. Similarly, fresh air is drawn through the re-circulating dampers 85 into the fan 70 and out through the exhaust air coil ~,5.
(f) Mixed FreshJ~e-circulating Air Mode-Cooling ==_~_m~~am~ » a~_m~~aa~__=a=___=_=__ Similarly to the mixed air heating mode, in the cooling mode mixed fresh and re-circulating air can be obtained by positioning the re-circulating dampers 05 and S~ in intermediate positions using the motor ~0. In this position, the coupling means 57 are again engaged, permitting concurrent operation of the face dampers X62 and bypass dampers 5~ to attain a desired flow of air in proportion to the instantaneous refrigerant condensing temperature. Similarly to the mixed air heating mode, fresh air entering the duct '75 through the main damper 62 is mixed with return air passing through the re-circulating damper 56, both o~ which then passes through the coil 1,~.
The balance of return air not passing through the re-circulating dampers 56 passes through the damper 92 and mixes with some fresh air passing through the dampers ~5 to be f ed through the ~eoi 1 ~.5 by the f an 7 0 .
Figures ~ through 6 The apparatus 10 can be incorporated into a single housing 100 so that the supply and exhaust portions are '°close-coupled'°, thus simplifying some construction.
Alternatively, the supply and exhaust partions can be separated and fitted into separate housings (not shown) hich are located in different portions of the building.
The description following relates to the close-coupled system which has certain advantages as will be apparent.
As seen best in Figure 4, the housing 1,00 is a generally rectangular structure having a supporting framework, side, top and bottom panels and access doors, not shown, where required to facilitate servicing. The housing ~~~ is divided internally by a main vertical dividing wall ~~12 which separates supply and exhaust portions ~.~4 and 1~5~respectively.
As also seen in Figures 5 and 6, the supply and exhaust fans 68 and 7~ are mounted in lower and upper 1~ portions of the housing l.Q~, so that the housing is also divided horizontally for purposes as will be described. ' Thus, the exhaust air coil 15 is located in a plane above the supply air coil ~6'and displaced laterally therefrom, and the bypass damper 58 is located above and displaced.
laterally from the face dampers 6~. The horizontal partition e~3 prevents mixing of the main flow in the inlet chamber ?5 and the bypass flow. Thus, the supply portion ~.0~ has the supply chamber 6°7 having main and bypass ducts for receiving separate streams of aiac, and the horizontal partition 73 maintains separate maim and bypass streams of air: The fan ~8 serves as propa~lsion means for generating air flow through at least one of the ducts.. Fresh air enters the housing through optional intake louvres ~.~~
which can be installed to minimize entry of rain or snow into the system.
As previously described with reference to Figures 2 and 3, and as seen in Figure 5, the inlet space 75 is defined in part by the face damper g~, the supply air coil 16 and the horizontal partition 73. The space 75 also has a side wall formed of the re-circulating dampers 85 (lower) which are coupled to the re-circulating dampers 85 (upper).
As seen in Figure 4~, the dampers 85 and 8~ are cantrolled by the motor 9~ and are opened when the apparatus functions in the re-circulating mode or mixed fresh and re-circulating mode as previously described. Thus; the vertical dividing wall ~0~ has an aperture.therein which is closed by the re-circulating dampers 85 and 88 when in the full fresh air heating mode as showia in Figure 2, or in the full fresh air cooling mode, not shown. However, the dampers 85. and 86 are fully or partially opened when in the full or mined re-circulating mode as shown in Figure 3.
Thus, it can be seen that the re-circulating dampers 85 and 86 5er'S7e as re-Circulat7.ng f low control means disposed between the supply chamber and the. main space. The re-circulating flow control means are settable 30 at either full open, full closed or at an intermediate setting in which the dampers ~~ anel s~ are partially open to attain the mixed flow. Th,~ re-circulating flow control means in effect form a first openable partition,.i.e. the first and second xe-circulation dampers 8S and 86, between the supply and exhaust chambers 6~ and 69 to permit communication therebetween when the re-circulating flow control means are open. This is shown in Figure 3, and to control flow it can be peen 'that the exhaust chamber 68 has a second openable partitionP namely the barometric dampers ~~ and the dace dampers ~2: The dampers 92 divide the exhaust chamber 69 into a return portion and an exhaust portion commuhicating with the sp~c~ to b~.heated and atmosphere respectively. ~'he return portion is bounded by the closed dampers 92 and 62, and at least some air from the main space is re°circulated through the dampers 86 and the coil 966. The exhaust portion is also bounded by the closed dampers 9~ and 52, and at least some fresh air is drawn through the open dampers 85 and the coil l5:
Thus, when the invention is assembled into a single unit as shown, the various dampers serve as a convenient openable partition means for diverting the air between adjacent chambers, depending on the mode cf operation of the system. This .simplifies considerably ducting and servicing, as the whole unit can be accessed and serviced in a compact space:

_~g_ Figures 2, 3~, 7 and 8 As seen in Figure 2, the face and bypass dampers 5Z and 58 are selectively mechanically connected together with the telescopic coupling means 57, and the dampers a2 are directly coupled to the modulating actuator 55. when engaged, the telescopic coupling means 57 rigidly interconnects the dampers 5~ and 6Z to operate in the inverse proportional relationship as previously described.
As seen in Figure 3, when the coupling means is disengaged, the bypass dampers 5~ are de-coupled from the face dampers 5Z, and are free to close automatically, while the dampers 6Z operate alone in response to actuation of the modulating actuator 55. The telescopic coupling means 57 has a provision to disconnect and reconnect the inverse proportional coupling between the face and bypass dampers which is for use in the re-circulating modes, see Figure 10 description.
Referring to Figures 7 and 8, the coupling means 57 comprises first and second rods aZl and l2Z which have outer ends coupled by radius arms, not shown, to the mean dampers 62 and bypass dampers~5~ respectively, not shown in Figures 7 and 8. The rods,lZ1 and 1ZZ have inner ends fitted with a magnet 1Z~ and an armature 1125 respective:Ly.
The magnet and armature 'are dzscs of generally similar sire, which are fitted for sliding movement within a tubular body 3Z7. The body has first and second end caps ~Z~ and X,30 fitted with aligned bores to receive the first and second rods ~.Z1 and ~.ZZ respectively and to enclose ends of the body 1Z7. preferably the magnet ~Z~ is a ceramic permanent ring magnet, and the armature &Z5 is a steel washer which is attracted to the magnet when in close proximity thexeta: Spacing ~3Z between opposed faces of the magnet and armature equals full stroke of the actuator 55 which is necessary to mote the dampers 58 between fully closed and fully opened positions.
The body ~Z7 has an axially aligned, elongated clearance slot 133 adjacent the end cap 13~ remote from the magnet, the slot extending inwardly from the end cap 130 to an inner end 135 of the slot. A bracket 13'7 is located adjacent the inner end 135 and journals a latching arm 139, which can slide into the slot as sa;en in Figures 7 and 8.
A transverse pin 13~ extends laterally through the arm and interferes with the bady 127 to prevent excessive movement of the arm 139 into the body. The arm 139 has an outer end 141 which has mutually. perpendicular longitudinal and radial faces 143 and 144, the terms longitudinal and radial referring to the body 127. In Figure 7, the coupling 59 is shown in an extended or disengaged position in which the damper 58 is de-coupled from the actuator .55, as.found in the re-circulating mode. In this position, the magnet 124 is adjacent the end cap 129, and the armature 125 is retained adjacent the end cap 130 by the latching arm 139 which has passed into the clearance slot i33 so that the radial face 144 is against the armature 125. ~ de-coupling stop 15~ is located on am adjacent surface 151 to prevent further movement of the means 5~ ~.n the direction of the arrow 1~~. The stop includes a bracket 153 with an adjusting screw g5~ which can be adjusted so that the screw A52 contacts the end plate 129 so as to hold the bypass dampers closed when the coupling means 57 disengages the actuator 5S (Figure 3).
Figures 7 and 9 throuaLh 11 Figure 9 shows the coupling means 57 in an engaged configuration in which the armature 125 is retained against the magnet 124 so that the rods 121 and 122 are effective axially joined together to function as a single rod. Single blades of the dampers.5~ and 62 are shown, the remaining blades .being coupled in accordance with common practice. The blade of the bypass dampers 58 has a bypass damper spindle 154 and a bypass damper radius arm or lever 155 extending therefrom. ~'he dampers are positioned so that the spindle is generally horizontal, and blades of the ~fl l~'~~'~

dampers are offset so as to be unbalanced so as to close under gravity, that is, the dampers 58 are gravity biased to automatically close. The blade of the face dampers 62 has a face damper spindle 9.56 and a.face dampex radius arm or lever 157 extending from the spindle as shown. The spindle l56 is similarly journalled horizontally, and the face dampers are coupled to an output shaft of the actuator 55 not shown. The first and second rods 9.21 and 122 are connected to the levers ~5?~ and 155 respectively so that 20 rotation of the spindle X55 by the actuator 55 results in a corresponding rotation of the spindle 154. Thus, when the coupling means 57 is engaged as shown in Figure 9, rotation of the lover 3.57 in an anti-clockwise direction per an arrow 158 restates the lever 155 in a clockwise direction per an arrow X59.
Referring to Figure 10, far the apparatus to shift from a full fresh air or mixed fresh and re-circulating air configuration to a full re-circulating configuration the dampers 58 and ~2 must de-couple as follows. The face dampers ~2 are rotated anti-clockwise towards a fully closecd position as shown by the arrow 158, which in train draws the rod 121 in direction of the arrow 3.48 which rotates the bypass dampers 58 anti-clockwise to the fully open condition. The stroke and length of the rods are adjusted so that bypass dampers' reach the fully open position before the face dampers are completely closed. Further travel of the rods 9.21 and 122 to fully close the face dampers exerts an excessive force between the magnet 124 and the armature 9.25, which force overcomes the magnetic attraction so that the rods eventually separate at.a threshold.position as seen approximately in Figure 10. This permits full closure of both the face dampers and the bypass dampers in the full re-circulating mode.
Referring to Figure 11, the spindle 9.56 of the face dampers 62 .continues rotation in direction of the arrow x.58 until the dampers 62 attain the fully closed position. When the armature 125 is released from the magnet, force from the gravity biased bypass dampers 58 rotates the spindle 154 in the direction of the arrow 1.58 and draws the rod 122 outwardly through the body 127 in direction of the arrow 1~~5 until the latching arm 139 and the armature t25 assume the position as shown in Figure 7.
In this position the bypass dampers are locked closed by both the latching arm 139 and the decoupler stop 3.50.
'The coupling means 57 permits either simultaneous inversely proportional movement of the dampers, or closing of the bypass dampers with independent opening and closing of the face dampers. Other means can be substituted to attain the same result, e.g. use of a separate, independently controlled actuatiar to control the bypass dampers. Thus, the coupling. means 57 further includes de-coupling means cooperating with the coupling means to de-couple the main flow control means from the bypass means as required, so as to cancel the inverse proportional relationship between the flow control mews. In summary, when coupled together, the first and second rods are operatively connected together to pravide the inverse relationslhip, and can be separated as required to permit closure of bypass dampers and independent operation of the main dampers.
The coupling means 57 can be retracted by reversing the above procedure, which occurs when the coupling means 57 is required to re-couple the face and bypass dampers. As seen in Figure 7, the rod 221 is moved axially inwardly into the body 12~ per arrow ~.~45, so that as the magnet 12~ approaches the armature x,25, the magnet pushes against the latching arm x.39, and across the longitudinal face ~,~3 swinging the arm outwardly through the slot in direction of an arrow 1~~. When the magnet ~.2~
contacts the armature x.25, the latching arm 239 is maintained disengaged from the armature 125. Thus, as the ~~'1~~~~'~
_32_ rod 121 moves outwardly in direction of the arrow 1~~, the armature and rod 122 can then move concurrently with the rod and magnet 12~, thus moving the entire coupling means to reopen the bypass dampers 58 as described.
Thus, in summary, when the armature 125 and the magnet 121 are in contact, the coupling means 57 is coupled or in retracted candition, as shown in Figure ~, and the bypass dampers move in inverse proportion to the face ~.0 dampers. However, when the coupling means 5~ is de-coupled by passing the thresh~ld position as shown in Figure 10, the face dampers become independent of the by~aass dampers which remain closed until the ~ cs~upling means S7 is re-coupled.
It can be seen ~th~t the body 127 serves as a guide means for guiding extension and retraction movement between the first and second rods 121 and 122. Also, it can be seen that the magnet and armature 12~ and 225 20 respectively serve as magnetic means for coupling together inner ends of the rods. The latching arm 1~~ serves as a retaining means fr~r retaining one r~d in a position while magnetic force coupling the rods together is overcome, permitting the rods to separate and de-couple the flow 25 control means.
Figure L.1~ ,-with some references to Figure ~.
The term "signal" herein refers to generation of 30 an electrical characteristic, or fluid pressure or equivalent which is used to actuate or enable a component.
The signal can change in magnitude and other characteristics ~s it passes through several components, but even after such changing it is still referred to as the 35 original signal. For example, an electrical signal when initially generated can be tao small, and requires amplification before usage. The numerical designation of such a signal does not change as it passes through the ~~"'l~'~~~°~
components which can change its characteristic.
A portion of an overall control system 160 is shown, in which the components are shown actuated for the heating mode. A room thermostat 161 is in the room or air space to ba heated and initiates a demand for heat when the actual temperature drops below a pre-set desired temperature commonly termed the thermostat set-point, but defined herein as a predetermined second reference 20 temperature as will be described. Hereinafter and in the claims, the actual temperature of the air space can be termed the °'actual.second reference temperature°°, and the pre-set desired temperature or thermostat set-point is termed "pre-determined eecond referenced temperature'°.
Difference between the actual and the pre--determined second temperatures is known as the set point deviation. The demand for heat initiates a thermostat output signal which has three functions which are considered as three separate thermostat signals from the thermostat 161 as follows.
In response to the actual temperature signal 65 from the sensor 5i (measuring the refrigerant condensing temperature), the proportioning controller 53, in turn generates the first control signal 56 to the modulating actuator 55 to control the dampers as previously described.
A first thermostat signal 162 is an enabling or ''changeover signal" which is fed along the lead 59 (Figure 1) to the damper relay 66 and then to the actuator 55 to enable the actuator 55. The signal~162 is °'low'° in the heating mode, and °°high" in the cooling mode, and also serves to switch the valve 34. The damper relay 66 is a DP/DT relay which can invert the first control signal 56 from the controller 53 as needed for cooling. In the heating mode, a damper relay output signal 61 is identical to the signal 56, whereas in the cooling mode, the damper relay 66 inverts the signal 56 ~thich causes signal 6l to be equal but opposite to the signalv56. Thus, during the cooling mode, the enabling or changeover signal i62 from the thermostat 2~~~~
a 168. to the actuator 55 is inverted by the relay 66 for reverse operation of the dampers 58 and 6~. The relay thus produces equal and opposite signals fox equal lower or higher deviations from the thermostat set point.
The room thermostat 16~ also generates a second thermostat signal ~6~ which is a voltage signal proportional to the set point deviation and is fed through a mu~.ti-contact relay X65 to a D~ amplifier 8.63 which 8.0 amplifies the signal and feeds it to the motor 6~4 which .
controls the modulating suction cut-off valve 37. 'rhe signal g3~ has a linear characteristic dependent upon user defined throttling rahge, and is present whenever set point deviation exists except when there is a negative set point deviation in the cooling mode, or a positive set point deviation in the heating mode, in which case the second signal 164 is at its lowest value (zero volts D~). The second signal 16~ is inverted and amplified as it passes through the amplifier L6~ and then fed to the motor 6~ to vary size of a flow restricting orifice in the valve 37.
With a full'heating demand, the valve ~'~'is maintained in a fully opened position to permit full flow of_refrigerant to compressor, and then to the condenser or supply coil ~6 (Figure 1) to provide maximum 'heat output from the apparatus to satisfy the thermostat demand. The second thermostat signal 164 represents the set point deviation, i.e. difference between an actual second reference temperature (i.e. the actual air temperature) and the desired air temperature or thermostat set point (previously defined as the predetermined second reference temperature) .
The difference between the actual second reference temperature and the predetermined second reference temperature is important to the invention and after processing is defined as the second control signal 16~.
Third and fourth thermostat signals 166 and 26~
are generated by the thermostat 168. and fed to an air proving switch 167 and interlocked thereby. Both signals 2~~~'~~'~ v _35_ 166 and 168 can be blocked by the air proving switch 167 if insufficient supply air flow through the supply fan 6~ is sensed. The third signal 166 continues through another air proving switch 169 and is further interlocked thereby.
The air proving switch 169 can block the signal 166 if there is insufficient air flow through the exhaust fan 70.
zf both air proving switches provide acceptable signals, the signal 166 then proceeds 'to a compressor protection circuit 171. Tt is further interlocked in the circuit 1'71 and then passes through a defrost.logic circuit 193 and eventually starts the motor compressor 12 if all interlocks are satisfied. The fourth signal 168 continues from the air switch 167 tb energize the auxiliary heater ~~ whenever the fourth signal is present and the interlock is satisfied.
The diagram shows that the reversing valve ~~ doss not receive a signal when the thermostat 161 is calling for heat as this is a biased valve which, when non-energized, is biased to the position shown in Figure 1, which as previously stated, discloses the heating mode.
The defrost logic circuit 173 provides demand defrost for the exhaust coil. The circuit 173 can be a known unit and has a group of components which sense when the axhaust coil 15 starts to accumulate frost, that is accumulate ice on the outside, which restricts flow therethrough. If ice accumulates, the demand defrost initiates a defrost cycle, and it also senses when the defrost cycle should terminate. Defrost lagie is passive until required, and is only normally required in the one hundred percent re-circulating heating mode. Because the exhaust coil 15, which is acting as an evaporator in the heating mode, will always be operating above 0°G (32°F) the exhaust air should never be less than 20°G (70°F) in the one hundred percent fresh air heating mode. But, should an exhaust fan air switch fail, the defrost logic will prevent a ~'snowball'° effect resulting in blocking the coil 15 with ice.

The operating motor 98 of the re-circulating dampers 85 and 8~ is controlled by a remote positioner 170 which is typically a three-terminal potentiometer which controls balancing relays or the electronic equivalent within a proportioning motor. The remote positioner x:70 positions the motor 90 to satisfy interior ventilation requirements of the building. at can be operated manually adjacent thermostat 16~, or can be an integral part of a thermostat 3.6~, or be substituted with automatic controls that proportionally respond to high interior humidity and/or carbon dioxide levels.
An end switch x;77 is an adjustable micro-switch which is actuated by the motor 9~ when the re-circulating Z5 dampers 85 and 86 (Figures 2 and 3) are less than ten percent open (e.g. effectively closed to prevent re-circulating). The switch 177 generates an end switch signal 1.7f which activates a decc~upling means x.75 to decouple the bypass dampers 58.
A shut-dawn rely x.73 is provided for an emergency situation such as might arise in .a fire. A
fire/smok.e detection switch 17~ is coupled to the relay 17~
and the relay X74 can be used to decouple bypass dampers 58 25 from the modulating actuator 55 by activating the decoupling means 175. The decoupling means can be an electrical signal Which simulates driving the face damper f~ to a closed position, which automatically decouples the bypass dampers rs as previously described with reference to 30 Figures '7 through 10. Alternatively, a signal can be generated which actuates the modulating actuator 55 to actually drive the face dampers to the closed position, which would also result in decoupling of the coupling means 57 as previously described. Equivalent means to permit 35 decoupling between the face and bypass dampers can be devised to suit particular installations. The relay 17~!
when actuated can class . the face dampers 6~ by actuating the motor 55 and also can class the re-circulating dampers 85 and 88 by actuating the orator 9~. This isolates the building from the outside, thus preventing any measurable flow of air into the building. The fans 88 and 78 are also stopped, which triggers the air proving switches 187 and 189 to shut down the compressor 3.~ and auxiliary heater ~~, thereby disengaging all heating and cooling equipment within the system.
For changing to the cooling mode, a signal from the thermostat 181 is fed to the reversing valve 3~
(Figure 1) to shift the valve ~~ to the apposite position, not shown. This reverses .flow in some conduits as described, and same of the system then operates as,a normal air conditioner. However, in the cooling.mod~, the motor 84 modulates the suction cut-off valve ~7 in response to the second signal as will be described. The auxiliary heater 82 is maintained de-activ~a~ted by the thermostat 181 as the fourth signal 188 is not present in the cooling mode.
OpEItFr~I°I OId (a) Full Fresh Air Mode-Heating Referring to Figures 1, 2 and 12, a description of one hundred percent fresh air heating mode is as follows. The fan 68 generates main and bypass streams of air which flow along the main duct 78 and bypass duct , ~3 respectively, the two streams of air being maintained separate from etch other by the partition 73. The main stream of air is directed through the coil ~e which acts as a condenser of vapour compression heat pump and heats the maiw stream of air.
The controller 5~ is pre-programmed by the installer to establish the pre°-determined base or first reference temperature which is the pre-determined or "ideal" refrigerant condensing temperature. This °'ideal"
temperature is a compromise between efficiency and comfort and is dependent upon the pressure of the system, type of refrigerant used and other parameters. The sensor 5~ is located on the outlet of the condenser coil 16 and thus detects actual refrigerant condensing temperature. The first actual reference temperature ~~ outputted by the sensor 59. is fed into the controller 5~, compared with the pre°determined first temperature and the difference is outputted from the controller 5~ as the first control signal 5~, as previously described with reference to Figure Z. This first ~antrol signal, is fed along the lead 5~ to the damper relay 6~, and is unchanged as the relay output signal 61,, and is fed to the actuator 55 which, as previously described, controls the dampers. It .is noted that the first thermostat signal l~~ is ineffective until the thermostat generates the third signal 1~6.
In response to the first control signal from the controller ~3, the actuator 55 positions the face dampers 62 and thus also positions the telescopic coupling means 57 to control opining of the dampers 5~ to control flow of the bypass air in response to the first control signal. Thus, if the first control signal. 56 reflects an actual first reference temperature 65 below the predetermined first reference temperature, the dampers .~2 close slightly, and the dampers 5~ open slightly so that the bypass flow is increased. Conversely, if the~first signal reflects an actual first reference temperature above the predetermined first reference temperature, the bypass flow is decreased by reversing the above damper movement. The final step of the,heating process is mixing the main stream of air after passing through the condenser 16 with the bypass stream of air, if any aim were passed through the bypass dampers 5~, prior to delivering the mixture of air streams to the space to be heated through the fan 6~. .~s described previously with reference to Figures 9 through 1~., the inverse proportionality between the bypass dampers 5~ and face dampers 62 permits cantrolling the main stream of air also in response to the first signal in an inverse flow ratio to -3~-the bypass stream of air. In this way, as flow through the bypass duct increases, flow through the main duct decreases and vice versa while maintaining constant volume flow of air into the space. It can be seen that the face dampers 62 and bypass dampers 5~ serve as main flow control means and bypass flow control means which cooperate with the main duct and bypass ducts respectively to control flow therethrough. Together, the dampers ~~ and 62 comprise air flow control means for controlling ratio of flow of streams 20 of air through the main and bypass ducts.
The second thermostat signal 1.6~ from the thermostat 161, after passing through the relay 1G~ and processing by the amplifier 163, a.s outputted to the motor 6~ to control flow in the suction line 36 by modulating the valve 3~. For a normal full demand'for heat, the valve 37 is maintained open, thus permitting normal maximum operation of the evaporator, that is, the extxaust heat exchanger 2.6 which is positioned upstream (i.e. with 2~ respect to refrigerant flow) of the compressor 3.~. As the actual second reference temperature (i.e. actual room temperature) approaches the predetermined second reference temperature, (i.e: the thermostat set point or desired air temperature) the difference between these temperatures diminishes. This difference is the second control signal 164, and the greater the difference, that is, the set poi:oit deviation, the larger the signal 16~. The larger the signal 164, the greater the movement of the valve 3'7 from the full open positi~n, and for a maximum signal, the valve 37 is fully closed, following compressor shut-down. As the restriction through the' valve is increased, flow of refrigerant through the valve decreases, causing the refrigerant vapour leaving the evaporator to be of rawer density than with a full flow valve. Thus, the evaporator operates .at an artificially high pressure while the compressor (which has an intake exposed to suction downstream of the modulating cut-off valve 37) operates at a lower than normal pressure, that is the compressor is ~0~~~~~~~
o-starved of refrigerant. Thus, the condenser heat rejection is reduced in proportion to control signal by inhibiting the ability of the evaporator to gather heat from air leaving the building in the exhaust stream.
Also, volumetric efficiency of the compressor is diminished in inverse proportion to the compression ratio which further reduces system capacity. The de-superheating expansion valve 2~ prevents compressor overheating while operating under these conditions f~r sustained periods by admitting a small amount of refrigerant into the compressor as required. It can be seen that the valve 37 is automatically positioned. in response to the second control signal ~.6~ from the thermostat 3.61 reflecting heating demand. As the heating demand decreases, the valve is gradually shifted proportionally towards the minimum flow position. Thus, the valve is modulated so as to balance the condenser heat rejection to the fresh-air heating load, thus maintaining a constant supply air temperature throughout throttling range of the valve 37.
As previously sated, the higher internal evaporator pressure caused by the throttling action of the valve 3~ results in a higher boiling temperature of the refrigerant passiaxg through the evaporator. This reduces the net temperature difference between the evaporator air stream which decreases the heat gatk~ered by the evaporator which in turn decreases the condenser demand ox heat rejection. As the total heat rejection at the condenser is equal to the heat gathered in the evaporator plus the heat of compression, it follows that heat rejected at the condenser, termed condenser demand, can be controlled by controlling the amount of heat gathered in the. evaporator.
The said modulation of the valve 3'7, which gradually reduces refrigerant flow, prevents cold ambient air from entering the building during continuous fresh-air supply. Use of the valve reduces considerably the off-cycle periods of the refrigeration plant when the refrigeration plant output would normally exceed the fresh-air heating demand. When the air space temperature is satisfied with respect to the second control signal, the compressor which is controlled by the third control signal is interrupted.
This is to prevent sustained compressor operation while the modulating valve is fully closed. When outdoor conditions and air quantity supplied exactly equal internal space requirements, a state of thermal balance exists, and the compressor is not required. Tt can be seen that the valve 39 effectively provides capacity control of a heat pump without a mufti-stage or mufti-speed compressor, and thus provides a considerable simplification and improved control precision over control systems of prior art heat pumps.
Thus, the heat pump maintains temperature in the room as controlled by the thermostat without surges of cold air which v would '.otherwise be generated when the refrigeration plant output is greater than the building heating demand as in prior art machines. As a consequence, the more uniform temperature resu3ts in less cycling "an and off" of the compressor, increas~.ng life of the motor and compressor.
Usually, a normal heating demand signal from the thermostat 261 positions the valve ~? to a fully open condition so that heating output is at a maximum. When the compressor initially starts to pressurize refrigerant, in response to the initial full demand of the second control signal from the thermostat, temperature at the sensing bulb ~4 is initially increased. This will cause the de-superheating thermostatic expansion valve ~~ to admit liquid refrigerant fra~i the liquid line ~7 into the suction line ~2, via the pressure vessel 30. This lowers the compressor discharge temperature, and high pressure heated vapour passes through the reversing valve 3~ into the vapour line ~8 towards the supply coil 1~. In the coil 16, the refrigerant condenses, passing heat into the supply 2_ air, and liquified refrigerant bypasses the expansion valve 45.through check. valve ~8 to arrive at the junction 2~.
Clearly, the temperature sensor 51 detects the temperature of this liquid refrigerant, which in eonjunction with the proportioning controller 5~~, positions the dampers as required. It is added that if the condensing temperature at the sensor Sl becomes too low, the proportioning controller 53 re-positions the face dampers to reduce flow through the coil 1~, and, through the inverse proportional coupling 5'7, opens the bypass dampers a~ to a wider position. to maintain constant air volume to the supply fan t~. In effect, the air quantity through the supply coil l6 is modulated by the face dampers. to attain optimum refrigerant condensing temperature. It is added that the thermostatic expansion valve 23 on the exhaust coil ~.5 functions in a normal manner, in response to outlet temperature from the exhaust coil as detected by temperature sensor 25.
When the liquid refrigerant passes through the expansion valve 23, the pressure in the exhaust coil lr drops so that the refrigerant boils and the resulting vapour gains heat from air dravan through the exhaust coil by tire fan 7~D. The resulting vapour is slightly super-heated and is drawn towards the compressor through the reversing valve 3~ and then to the modulating suction cut-off valve 3?. As stated previously, the cut-off valve 37 partially controls the compressor compression ratio and thus the heat gathered and rejected, as well power consumed by the compressor: Gas drawn through the valve ~7 basses into the pressure vessel 3~ which traps liquid refrigerant to avoid being drawn into the compressor. The compressor is suction cooled, but if the compressor begins to overheat, the de-superheating expansion. valve ~~, controlled by the sensor ~~, will admit sufficient liquid refrigerant into the suction line to lower the gas superheat to cool the compressor. Usually, the only tame this would occur would be during prolonged periods of compressor operation at minimum load.

~'~~'"~'"~

In summary, the above description relates to operation of the apparatus, in the full fresh air heating mode wherein operation~of a refrigeration plant operating in reverse as a heat pump is enhanced by three distinct and independent optional aspects as follows:
(i) The first aspect is to maintain constant volume of flow into the space by using face and bypass dampers to control flow through two parallel inlet ducts. The dampers are modulated in inverse proportion to each other in response to the first control signal generated by refrigerant condensing tem~aerature. This permits matching of the rates of condensing (in heating mode) and I5 evaporating (in cooling mode) ~f the refrigerant so that if the condensing temperature becomes too low, air flow, through the condenser is reduced by increasing flow in the bypass duct, thus matching heat gathered at the evaporator with heat removed at the condenser.
(ii) The second aspect of the invention. relates to system capacity control by gradually reducing heat output from the condenser as the room temperature rises to attain the desired room temperature, that is as set point deviation decreases and approaches zero. The set point deviation generates a second control signal which is used to modulate the suction cut-off valve 3'3 disposed between the evaporator and the compressor intake, so that as the set point deviation decreases, restriction of flow from the evaporator to the compressor is increased. The flow restriction maintains an artificially high pressure over the evaporator, thus raising evaporator temperature and simultaneously reducing mass flow of refrigerant through the compressor due to decrease in density of the -~4-refrigerant due to the restriction. l'hus, less heat is removed in the evaporator, and correspondingly, less heat is available at the condenser, enabling a tapering effect of heating until the set point deviation is zero.
iii) In the fresh ai.r and mixed fresh/re~-circulating air heating modes, the exhaust heat exchanger (the evaporator) c~pturss some heat Exam the 2.0 heated air an the space, before the heated air is exhausted to- atmosphere. Capturing this heat increases overall ef~i~iency of the unit vahen compared with locating the evaporator in, anothex, usually solder, heat escchange medium, such as outside air.
b) Full Re-circulating Air Mode-Heating As briefly described previo~aly, in the furl ~e circulating mode, as seen i~ Figure 3, da.sconnection o~ the coupling means 5~ results in full automatic closure of the bypass dampers 5~, and independent operation of the face dampers fe2 in x°esponse to the first .signal fed into: the actuator 55. All heated return air from the room passes through the re-circulatingy dampers 86, and then through the heat exchanger 1.6 under the. influence of the fan t8. Fresh air passes through the pre-°filter ~2 and the re~-circulating dampers 85 under-the influence of the fan '~8, and i.s then passed through the exhaust heat exchanger 15. As with.the full fresh air heating, the suction cut-off valve ~7 is modulated in response t the set point devi.atian,.thus obtaining the benefits as previ:ouslx described.
(c} Full Fresh Air arid Full Re-circulating .
Air Modes-fooling The above three features have equivalent applications also in the cooling mode, and provide similar but opposite advantages to those in the heating mode, and are briefly described as below. As in the heating operation, much of the cooling operation follows conventional practice and is not described in detail. The main differences relating to the~three aspects of improved cooling are described briefly as follows.
In response to the temperature signal from the 1~ sensor 5~., the proportioning controller 53 in turn generates tf~e first control signal 56. To initiate a cooling cycle, the first thermostat signal l62 to the actuator 55 is fed along the lead 59 and to tine damper relay ~~ so ws to enable the actuator 55. As this is in the cooling mode, the signal if>2 is high, causing the damper relay 6~ to invert the signal 56 from the controller 53 into the inverted output signal ~1, which is fed to the modulating actuator 55 to control the dampers 62 and 5~ in a reverse mode to that used in the heating mode as follows.
The ''high'' signal X62 also switches the valve ~~ for cooling. Thus,'in the cooling mode, the exhaust coil 15 is now a condenser and r~je~;ts heat to exhaust air-leaving the space, at least in.the full fresh air or mixed fresh and re-circulating air mode. If there is insufficient cooling of the condenser by the exhaust air, refrigerant condensing temperature will rise and this will affect the first signal generated by the temperature sensor 53~ in the exit from the exhaust coil 15. The face and bypass dampers will then respond in the opposite direction with respect to the heating mode, that is he face dampers 6~ will tend to close, thus,reducing air flow through the supply coil 16, acting as an evaporator, and instead increasing flow through the bypass duct. This tends to reduce heat gathered at the evaporator, which in turn xeduces condenser demand or heat rejection requirement at the condenser, and thus reduces overloading of the system. Thus, rates of evaporation and condensation are now matched.

~46-The second thermostat signal 1~~ represents the set point deviation, that is difference between the actual air tempe~eature and the desired air temperature or thermostat set point. The second thermostat signal 1~~ is fed to the relay 165, to the amplifier 1~3, and then to the motor 6~ which controls the modulating suction cut-off valve 37. With a full cooling demand, the valve 3~7 is maintained in a fully opened position to permit full flow of refrigerant from the evaporator, namely the supply heat exchanger 15, to the intake of the compressor, to provide maximum cooling to satisfy thermostat demand. The third and fourth thermostat signals 3.~6 and 1~~ function as similarly described fhr the heating mode, as does also signals through the degrost logic circuit.
As the actual room tegnperature lowers towards the desired roam temperature, set point deviation decreases and the second control signal to the modulating valve is gradually reduced. This gradually increases restriction of valve 3~ which reduces flow through the valve 3?, thus increasing evaporator pressure, and thus artificially raising the evap~rati.ng temperature, which in turn reduces the cooling affect of the evaporator and thus temperature of cooled air increases gradually: In this way, the air temperature discharged from the air conditioner system more gradually approaches the set point temperature; resulting in more uniform cooling, in a manner similar to the more uniform heating of the previously descrilaed heating mode.
In the full fresh air mode only, as previously described, cooled return air from the room passes through the exhaust soil ~:5 (condenser] and, as it is usually at a lower temperature than ambient air, will result in improved cooling of the condenser and thus improving overall efficiency of the system, due to recapturing some of the "low temperature" from the exhausted air prior to passing to atmosphere.

~0~~~~~

(dj Mixed/Fresh Re-circulating Air Mode-T3eating and Cooling As previously discussed, a third mode, namely a mixture of fresh and re-circulating air, can be obtained by partially opening the re-circulating dampers ~5 and ~~, in combination with modulation of the face and bypass dampers ~2 and 5~.
1o Referring to Figure 3, in the mixed air heating mode, fresh air. pissing. through the pre-filter 71 is divided into a first portion passing through the bypass duct 79, a second portion passing through the face dampers 6~ and thus into the mai.n~dudt 76, both portions being drawn by the fan 6~, and a third portion passing through the partially open re-circulata:ng dax~pers 85 under the influence of the fan '?~. As in the full fresh air heating mode, the dampers 62 and 5~ are proportioned in accordance with the first control signal, and fresh aid passing through the supply heat exchanger 1~, now operating as a condenser, is heated and discharged, together with the bypass stream by the supply fan ~8 into the apace to be heated.
Return air from the space also enters the unit, and a first portion e~f the x°eturn air passes through the barometric dampers ~~ under the influence of Iow pressure generated by the exhaust fan ~~, to be mixed with the third portion of fresh air passing through the re-circulating dampers ~5. lBath exhaust and fresh as.x are mixed in the fan 7~ and then pass out through the exhaust heat exchanger 15, now act~.ng as the evaporator. The return air passing through the ~e-circulating dampers ~6 is mixed with the second portion of the fresh ~ air passing through the face damper ~2 and thus ~seists in warming 'the fresh air passing through the supply lheat exchanger or condenser I~. As the room air will be warmer than the outside air, condenser temperature wil l rise, thus reducing demand from the heating system and permitting recovery of some energy frJm the exhaust air. If the condensing temperature should drop due to excessively cold fresh air entering the system, the face dampers dZ will tend to close, while the bypass dampers 58 will tend to open as before. As long as the pressure drop across the supply heat exchanger 3.6 remains essentially constant, volume of return flow through the dampers 86 into the main duct ~~ should remain constant, regardless of the air flow through the bypass duct.
l0 dearly, volume flow of air entering. the exhaust fan 7el is the combination of flow of heated exhaust air flowing through the barometric dampers 92, and cooler fresh air flowing through the re-circulating dampers .85. The mixing of these two flows by the fan 7~ produces a warmer flow of air through the coil 15 than if fresh air alone were used, thus permitting recovery of some energy from the exhaust air. Thus, the mixing or' combination of flows passing through the supply or exhaust fans permits recovery of some heat energy while also providing some fresh air.
While the re~-circulating dampers 85 and 8~ are shown coupled, so ws to open and close equally, for some mixed air applications it might be desirable to have a non-linear relationship between the dampers 8S and 86. Any excess air pressure in the building can be automatically exhausted through the barometric dampers ~~, to prevent excessive internal pressure. Thus, in summary, the method incorporating mixed./re-circulating air is characterized by admitting return air from the space into the main stream of air to pass through the supply heat exchanger, while concurrently admitting fresh air into at least the bypass stream, and concurrently discharging return air from the space together with fresh air through an exhaust heat exchanger.
Tn the mixed fresh/re-circulating air mode with cooling, similar but opposite actions of the face and bypass dampers are achieved thus improving matching of the evaporator and condenser as previously described. In both -49_ heating and cooling in the mixed mode, the advantages of modulating the suction cut-off valve 37 in response to set point deviation are attained, producing the previously described tapering effect of heating ar cooling as the set point deviation approaches zero.
As discussed previously with respect to the ful l re--circulating heating mode, in the mixed mode, air passing through the evaporator is warmer than outside air, and thus facilitates gathering of heat for the evaporator which increases system capacity considerably. Also, similarly to the full re--circulating mode previously described, heat pump defrosting is simplified due to the higher temperature of air passing through the evap~rator coil.
With respect to the cooling mode when using mixed re-circulating and fresh air, as in the full re-circulating cooling mode previously described, the mixed air discharged through the exhaust heat exchanger, i.e. the cohdenser,~is cooler than outside air sahiGh pr~vides an improved heat sink for the condenser coil: The cooler the air passing through the condenser, the easier for rejection of heat and this also increases system capacity.
In summary, the mixed re-circulating and fresh air mode permits improved heat gathering or rejection due to the location of the exhaust cola 15 in the floaa of air from the room, which provides a more favourable temperature for a heat sink or heat gathering than with a coil exposed to normal outside air fnr cooling or heating> While the energy recovery benefi~s~ in the mixed re-circulating and fresh air mode is less than in the full re-circulating mode, it is nevertheless a great improvementy over conventional mixed air systems and many energy saving benefits can be attained.

I f~

~~~' ~~~l~gv~a~
The above describes an apparatus and method for treating air, that is either heating or cooling the air, within an air space within a building. The air can be either 100 per cent recirculated within the building, 100 per cent fresh air drawn in from the outside and discharged outside after passing through the space, or a mixture of fresh and recirculated air. Clearly, in specific applications where the various comlaina~~.ons above described are not required; the apparatus can be simplified considerably by having only the desired mode. However, in temperate panes, and where building regulations require a supply of fresh air of usually more than l0 per cent, the full range of options discussed above provide the best results.
While some of the advantages above are related to a close coupled system housed in a single housing 100, many of the advantages can also be attained if the supply and exhaust systems are separated. Tn suah a separated arrangement, additional duct~.ng would be required, but the two aspects of the invention would function essentialJ.y identically> In an alternative arrangement, which provides only one hundred percent fresh air heating and cooling, the supply flow section can be remotely located with respect to the exhaust flow section, and the dampers ~5 and ~6 are not required as there is no re-circulating mode. Consequently, the sides of the flow sections are replaced with solid panels and two flow sections are interconnected with refrigerant line sets. This eliminates extra daact work that would otherwise be required if the units were close coupled, and permits the supply and exhaust flaw sections to be~located at the most convenient locations within the building. Also, for a system dedicated to fresh air mode only, with' no re-circulating, the decoupling of the coupling means 57 would not be required, unless it was necessary for closing the dampers for complete isolation of m51-the system from the outside, for example, during an emergency or fire shutdown.
The present apparatus as disclosed receives two main control signals which initiate and control the heating sequence and operation of components. The first control signal 55 is generated by the controller 53 (in response to the signal 65 from the senior 5~) and reflects difference between actual and pre-determined refrigerant condensing temperatures. This first control signal, via the modulating actuator 55, controls the face and bypass dampers to control temperature, and thus pressure of the refrigerant in the supply coil. The sensor 51 would normally be positioned in a location to detect actual refrigerant condensing temperature, i.e. at the exit of the condenser. This location is the preferred location of the sensor 51, but temperature at other locations in the supply coil could also be used. As 'air leaving the supply coil reflects, to some extent, refrigerant tsmporature in the supply coil, it could be possible, for some applications, to locate the sensor 51 directly in. the air stream from the supply coil. Clearly, in tha.s location, the thermostat should be relocated elsewherem inThile the sensox 51 is a temperature sonsor, an alternative pressure senior could be used to detect pressure on the high pressure side of the system.
Preferably, the pressure ~enso~ would be located in the compressor output line ~O, and this can be used as a substitute to generate the first control sa.gnal to cantrol the controller 53. This follows because the characteristic of the refrigerant ,can be assessed by either measuring temperature or pressure, as is well known in the art.
In some applications, it might be possible to eliminate one temperature or pressure sensor, and instead provide a combined signal which could be suitably adjusted to actuate both the actuator 55 and the m~d~.:lating valve 37.

The invention discloses variable face dampers 52 which control the main flow of air through the supply coil 9.~ in inverse proportion to flow through the bypass dampers, thus maintaining essentially constant total air flow into the air space. In some applications, the variable face dampers could be .eliminated, and flow through the supply coil could be effectively controlled remotely by the bypass dampers 5~. In this way, ratio of main to bypass flow would be dependent on the relative resistance between flow through the bypass dampers, and flow through the supply coil. Tt is considered that this alternative would be considerably less sensitive and more difficult to control than the preferred embodiment as disclosed as the total air flow rateo would very depending on the position of the bypass dampers and relative resistance to flow.
Also, the modulating valve 3~ is provided to permit greater control of operation of the compressor by controlling refrigerant flow and pressure, and thus greater control of heat recovered and heat rejected. Tn some applications the naive 37 could be eliminated, permitting the compressor to funct~.on without .this additional control.
however, for normal temperate climates where occasionally only a small function of system heating capacity is required, use of the modulating suction cut-off valve 3'7 is preferred as there are less temperature fluctuations in the discharge air as the thermostat set-point is gradually attained.
The invention is disclosed showing an essentially constant volume flow through the supply chamber. This constant flow is attained by proportioning volume flow between the main duct and tho bypass duct by controlling the respective main dampers and bypass dampers in ~n inversely praportional relationship. This is the preferred combination for most installations, and energy efficiency thereof is further improver~ by providing the modulating suction cut-off valve 37 which reduces heat rejection at the condenser. For some applications, where multiple or unloading compressors are not used, use of the modulating suction cut-off valve ~~ as a means of capacity control for a heat pump can be employed with a considerable saving in cost, and in some ~.nstances, improvements in efficiency. In some alternate installations, where constant air volume flaw is xiot of importance, the bypass flow duct and associated modulating bypass dampers 5~ can be eliminated, and all air flow then passes through a single duct. In this 1~1 alternative, capacity control using the cut-off valve 37 might be sufficient to provide an improvement over prior art methods for both heating and cooling.
In other installations, the telescopic coupling ~5 means 57 coupling the dampers 5~ to the dampers ~2 can be eliminated where one hundred percent re-circulating and fresh air options are required. In this instance, another actuator could be directly coupled to the bypass dampers 5~, and an alternative. means to permit simultaneous closing 2~ of both the face and bypass dampers would be required.
Also, in some installations where .one hundred percent re-circulating is desired, the coupling 5! could be eliminated, and the re-circulating dampers ~5 and ~6 could 25 also be eliminated. When one hundred percent re-circulating is not required, the actuator 55.could be directly coupled to the bypass dampers 5r8 by way of a solid rod, thus eliminating the option for uncoupling the bypass dampers.
30 The temperature sensors cooperating with conduits carrying refrigerant are expanding bulb types connected with capillary tubes to valves or other control means.
While this is the preferred means of detecting temperature of the refrigerant, clearly equivalent temperature sensors 35 could be substituted, for example sensors which directly generate electrical signals which are then used to actuate valves or related controls. Also, the thermostat of the control system as described is a preferred currently ~, _~~_ available unit which generates a plurality of signals for actuating or enabling other components of the system.
clearly, alternative control eystems with similar functions can be substituted.
The exhaust air coil ~.5 is disclosed for location in the exhaust chamber ~~, and thus receives a stream of treated inside air exhausted fram the room. ~dhile this location of the exhaust co~.l is preferred because some room heat can be recovered from the exhaust air in.the heating mode, and improved cooling generally xesults in the cooling mode, alternative locations of the exhaust coil are envisaged. Clearly, the exhaust coil can be located to be exposed to ambient or outside air as in a conventional air conditioning system, and this might be appropriate in certain installati~nsa Also, heat could be gathered by the exhaust coil from waste water or a ground heating source.
To reduce laad on the condenser and/or to obtain warm water for other purposes, an auxiliary coil could be placed in series with the discharge line 40 Figure 1).
ane purpose of this accessory would be to heat or preheat hot water tank makeup sc that some relatively warm water could be generated when the system is running, independently of the mode of operation, that is, when it is operating in either heating or cooling. The amount of heat rejected by the re~rig~rant could be controlled by controlling the flow of cooling medium, that is water through the heat exchanger which, in some installations could cause refrigerant de-superheating in the auxiliary heat exchanger, and in some instances could also cause s~me condensations This would reduce load on the condenser in high demand situations, which would reduce modulation of the face dampers in the.coolingr mode only. Clearly, when using the auxiliary heat exohange coil in the heating mode, less heat will be available for the room heating.
As an additional alternative, the temperature sensing bulb 4~ which is shown in the discharge line ~~ in Figure 1, could be relocated on the suction line ~2, and in this way, would c~ntral suction temperature which would indirectly prevent high compressor discharge temperatures.

Claims (21)

1. A method of treating air comprising the steps of:
(a) generating main and bypass streams of air, and initially maintaining the two streams of air separate from each other, (b) directing the main stream of air through a supply heat exchanger of a vapour compression machine to change temperature of the main stream of air, (c) generating a first control signal representing a difference between an actual first reference temperature and a pre-determined first reference temperature, (d) controlling ratio of flow of the main and bypass streams of air in response to the first control signal so that if the first control signal reflects an actual first reference temperature below the pre-determined first reference temperature, the main flow is decreased if heating the main flow, or increased if cooling the main flow; and if the first signal reflects an actual first reference temperature above the pre-determined first reference temperature, the main flow is increased if heating the main flow, or decreased if cooling the main flow, (e) mixing the main stream of air after passing through the heat exchanger with the bypass stream of air prior to delivering the mixture of air streams as required to a space.

2. A method as claimed in Claim 1, further comprising:

(a) controlling the main stream of air in response to the first control signal in an inverse flow ratio to the bypass stream of air, so that as flow through the main duct increases, flow through the bypass duct decreases and vice versa.

3. A method as claimed in Claim 1, further comprising:

(a) generating a second control signal reflecting difference between an actual second reference temperature and a pre-determined second reference temperature, (b) controlling heat exchange at the supply heat exchanger of the machine in proportion to difference between the actual second reference temperature and the pre-determined second reference temperature.

4. A method as claimed in Claim 3, in which:

(a) controlling the heat exchange at the supply heat exchanger by controlling heat gathered in an evaporator of the vapour compression machine from air passing through the evaporator.

5. A method as claimed in Claim 1, further comprising:

(a) generating a second control signal representing a difference between an actual second reference temperature and a pre-determined second reference temperature, (b) gradually varying flow of refrigerant to a compressor of the vapour compression machine in proportion to difference between the actual second reference temperature and the pre-determined second reference temperature.

6. A method as claimed in Claim 2, wherein the first reference temperature reflects difference between actual temperature of circulating condensed refrigerant and a predetermined condensing temperature.

7. A method as claimed in Claim 1, wherein the second reference temperature reflects difference between actual temperature of air delivered and mixed in the space and a predetermined space temperature.

8. A method as claimed in Claim 1, further characterized by:

(a) exchanging heat between air being exhausted from the space and refrigerant.

9. A method as claimed in Claim 1, further characterized by:

(a) admitting return air from the space into the main stream of air to pass through the supply heat exchanger, while concurrently admitting fresh air into at least the bypass stream, b) discharging return air from the space together with fresh air through an exhaust heat exchanger.

10. An apparatus for treating air for delivery to a space, the apparatus comprising:

(a) a supply chamber having main and bypass ducts for receiving and initially maintaining separate main and bypass streams of air respectively, (b) propulsion means for generating air flow through at least one of the ducts, (c) a supply heat exchanger of a vapour compression machine provided in the main duct to change temperature of the main stream of air passing along the main duct, (d) first temperature sensor means for generating a first control signal representing difference between an actual first reference temperature and a pre-determined first reference temperature, (e) air flow control means for controlling ratio of flow of streams of air through the main and bypass ducts, (f) actuator means for actuating the air flow control means so as to vary ratio of restriction to air flow through the main and bypass ducts, the actuator means being operatively coupled to the air flow control means and being responsive to the first control signal, (g) mixing means for mixing outlet flows discharged from the main and bypass ducts prior to discharging the mixed streams of air into the space.

11. An apparatus as claimed in Claim 10, in which:

(a) the air flow control means comprises main flow control means and bypass flow control means cooperating with the main duct and bypass duct respectively to control flow therethrough, and the apparatus further comprises:

(b) coupling means coupled to the main flow control means and the bypass flow control means so that the bypass flow control means is actuated in an inverse relationship to the main flow control means.

12. An apparatus as claimed in Claim 10, further comprising:

(a) second temperature sensor means for generating a second control signal representing difference between an actual second reference temperature and a pre-determined second reference temperature, (b) heat exchange control means for controlling heat exchanged at the supply heat exchanger, the heat exchanger control means cooperating with a compressor of the vapour compression machine so that heat exchange is in proportion to difference between the actual second reference temperature and the pre-determined second reference temperature.

13. An apparatus as claimed in Claim 12, in which:

(a) the heat exchange control means is a fluid flow modulating valve cooperating with a conduit communicating with an intake of the compressor of the vapour compression machine, the fluid flow modulating valve being responsive to the second temperature sensor so that as the actual second reference temperature gradually approaches the pre-determined second reference temperature, flow of refrigerant through the compressor is gradually reduced so that heat exchanged at the supply heat exchanger is correspondingly gradually reduced.

14. An apparatus as claimed in Claim 11, further including:

(a) the main flow control means being located in the main duct and spaced upstream from the supply heat exchanger to define an inlet space therebetween with the main duct, (b) re-circulation flow control means disposed between the inlet space and the space receiving the treated air, the re-circulation flow control means being settable at or between open or closed positions.

15. A apparatus as claimed in Claim 14, in which:

(a) an exhaust chamber communicates with the main space to receive air being exhausted therefrom, (b) the re-circulating flow control means forms a first openable partition between the supply and exhaust chambers to permit communication therebetween when the re-circulating flow control means are open.

16. An apparatus as claimed in Claim 15, in which:

(a) the exhaust chamber has a second openable partition to divide the exhaust chamber into a return portion and an exhaust portion communicating with the main space and atmosphere respectively, (b) the main flow control means can be closed together with the second openable partition when the re-circulating flow control means are open in the re-circulating mode to direct return air from the space back into the space.

17. An apparatus as claimed in Claim 11, further including:

(a) de-coupling means cooperating with the coupling means to de-couple the main flow control means from the bypass means as required, so as to cancel the inverse relationship between the flow control means.

18. An apparatus as claimed in Claim 17, in which:

(a) the coupling means includes first and second rods operatively connecting together the bypass flow control means and the main flow control means to provide said inverse relationship, (b) the de-coupling means is operative to separate the rods when required.

19. An apparatus as claimed in Claim 18, in which the coupling means comprises:

(a) guide means for guiding extension and retraction movement between the first and second rods, (b) magnetic means for coupling together inner ends of the rods, (c) retaining means for retaining one rod in a position while magnetic force coupling the rods together is overcome, permitting the rods to separate and de-couple the flow control means.

20. An apparatus as claimed in Claim 17, in which:

(a) the bypass flow control means is releasably coupled to the main flow control means to permit de-coupling therefrom, (b) the bypass flow control means are normally biased to a closed position so that when de-coupled from the main flow control means, the bypass flow control means automatically close.

21. An apparatus as claimed in Claim 10, in which:

(a) an exhaust heat exchanger is located in an exhaust portion communicating with the space receiving the treated air.