US20090151388A1

US20090151388A1 - Dedicated heat recovery chiller

Info

Publication number: US20090151388A1
Application number: US12/270,668
Authority: US
Inventors: Mark PLATT; Benny L. Kincaid
Original assignee: Multistack LLC
Current assignee: Multistack LLC
Priority date: 2007-11-13
Filing date: 2008-11-13
Publication date: 2009-06-18

Abstract

A heating and/or cooling system which incorporates one or more modular dedicated heat recovery refrigeration units each of which includes at least one compressor, an evaporator and a condenser. The system captures and utilizes condenser circuit heat which would otherwise be wasted. A variable speed circulating water pump circulates water through each evaporator/condenser, which are connected in parallel across the respective supply line and return line. A master controller activates and deactivates individual compressors in accordance with load demand. Shut-off valves close off the water flow through the respective evaporator and/or condenser of any units deactivated and the resulting changes in the pressure differential in the supply and return lines is sensed by sensor which sends a signal to the pump motor speed controller which changes the output of the pump to restore a predetermined pressure differential.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to improvements in heating and cooling systems and relates particularly to improvements in air conditioning and chilling systems. Particularly, the invention relates to a dedicated heat recovery chiller and control systems for such a chiller.
The dedicated heat recovery chiller and control system of the present invention utilizes heat otherwise rejected and wasted from a condenser circuit of a refrigeration system to offset heating load which would otherwise need to be provided from a heating source. This system raises the overall thermal efficiency of a building system, reduces energy consumption overall, and saves energy costs.
Recent developments in air conditioning systems involve the utilization of modular refrigeration units each having an evaporator and condenser in heat exchange relation with the fluid to be cooled and/or heated. With the modular system, each refrigeration unit is provided with headers for supply and return of the heat exchange fluid. A plurality of refrigeration units is connected in parallel, and the heat exchange fluid circulates through each evaporator and condenser heat exchanger.
The control of such a modular system enables individual refrigeration units to be operated in accordance with the load on the system. Thus, in times of high load, all refrigeration units will be operating to provide a specific heating and/or cooling capacity. When the load is reduced, refrigeration units may be down loaded, or made inoperative, thus reducing the operating costs of the system and resting units which are not required.
These units are interconnected and coordinated in the present invention to create a dedicated heat recovery chiller system. In this system, heat normally rejected to atmosphere from the condenser circuit of the refrigeration cycle is instead captured, controlled, and utilized to displace heat load otherwise provided by a conventional heating circuit.
2. Description of the Related Art
In the past, heat from the condenser circuit of an air conditioning system would be rejected to atmosphere, and thereby wasted.
The modular refrigeration system overcomes a number of disadvantages of previous systems, particularly with regard to system breakdowns and system expansion. The modular system also provides substantial economies in being able to operate only those refrigeration units necessary for the load at any particular time. Power is therefore saved in not having to run refrigeration units which are unnecessary, or in running units at lower than optimum peak operating efficiency.
With a modular heating and/or cooling system, however, the heating and/or cooling heat exchange fluid, which is usually water, passes through the heat exchange fluid manifolds supplying the heat exchange fluid to each of the refrigeration units. The pumping capacity required, therefore, for both heat exchange fluids, i.e., the heat exchange fluid through the evaporators and the condensers of each refrigeration unit, is necessarily that for supplying fluid through all refrigeration units and, preferably, is of greater capacity allowing for expansion of the system both in terms of the number of refrigeration units and/or the load requirements.
It is desirable to provide a dedicated heat recovery chiller system to improve the overall thermal efficiency of a building system.
It is desirable to provide a heating and cooling system in which water pressure differentials and water flow through the heating and/or cooling system is maintained substantially constant.
It is also desirable to provide an improved heating and/or cooling system for a modular refrigeration system having a multiplicity of refrigeration units in which the flow of heat exchange fluid through the condenser and/or chiller of each unit is dependent on the operating state of that unit.
It is also desirable to optimize the power consumed by a modular refrigeration system when operated at less than maximum capacity by reducing the flow of heat exchange fluid through the system.
It is further desirable to reduce the flow of heat exchange fluid through heat exchangers of modular units which are not operating and, at the same time, maintain substantially constant pressure differentials throughout the heating and/or cooling system.

BRIEF SUMMARY OF THE INVENTION

According to the present invention there is provided a heating and/or cooling system comprising one or more modular dedicated heat recovery refrigeration units each of which has at least one compressor, an evaporative heat exchanger and a condenser heat exchanger, supply and return manifold on each unit for conveying a first heat exchange fluid, the manifold being connected to manifold of adjacent units, supply and return fluid conduit extending between respective supply and return manifold of each unit and the associated evaporative heat exchanger so that the evaporative heat exchangers are connected in parallel across the interconnected manifolds, pump for the first heat exchange fluid, said pump including structure to vary the flow of the first heat exchange fluid, and valve structure to selectively close at least one of the supply and return fluid conduit structure.
Preferably, the pump is a variable speed or variable capacity pump circulating the first heat exchange fluid through the system. In one particular arrangement, control structure which controls the operation of the individual duration units determines changes in load conditions, such as through changes in return water temperature, conditioned zone temperatures, ambient temperatures, and the like, and controls the operation of the individual units in accordance with the load requirements. As the load decreases, individual refrigeration units are shut down. When a unit compressor is deactivated, the valve associated with that unit closes the fluid conduit so that the evaporative heat exchanger is no longer connected in parallel with the remaining heat exchangers. This causes a change in the differential pressure between the supply and return manifolds. The pressure change is sensed and the pump is varied to return the pressure differential to a predetermined level.
By using a variable speed or variable capacity pump, the power requirements for the pump is able to be reduced during reduced system load. Thus, as the load decreases and modular units are made inactive, the valve on those inactive units is selectively closed to thereby close the heat exchangers thereof to the heat exchange fluid. The power supplied to the pump is then also reduced due to the reduced pumping load resulting from a reduced number of heat exchangers in the circuit.
In one form of the invention, the valve comprises a valve provided on the return conduit of each unit. In another form of the invention, the valve comprises butterfly valves on both or either the supply and return conduit.
In a particular, preferred form of the invention, first and second supply and return manifold are provided for both the evaporator heat exchanger and the condenser heat exchanger of the modular units. The manifold comprise header pipes mounted on each unit with releasable pipe connectors at each end, such as those produced by Victaulic, which enable the header pipes of adjacent units to be connected together. However, it is to be carefully noted that the structure for connecting the pipes may be of any conventional structure. Welded ends, flanged ends, bolted ends, compression couplings, chemical adhesives and/or sealants, and any other standard coupling structure is contemplated by the present invention. The supply and return conduit are connected into the respective supply and return header pipes so as to provide a fluid path from the supply header pipe through the supply conduit, the heat exchanger and return conduit to the return header pipe.
The valve is preferably located in the return header pipe and is actuated to close the return conduit where it connects with the return header pipe. In one form of the invention the valve has a valve head to close the entrance of the return conduit into the return header pipe, a valve stem extending diametrically and through a seal on the opposite side of the header pipe into a pressure chamber located thereon, a piston on the end of the valve stem, and a bleed line extending from the supply header to the pressure chamber whereby fluid under pressure from the supply header pipe may be applied to the top of the piston to move the valve into the closed position. A pneumatic, hydraulic or electrical actuator valve in the bleed line controls the flow of fluid from the supply header to the pressure chamber.
With this arrangement, by operation of the relatively small electric, pneumatic or hydraulic valve on the pressure bleed line, fluid under pressure from the supply header pipe is able to be used to actuate the valve to close the return conduit. The valve may be opened by closing the electric, pneumatic or hydraulic valve which enables the pressure of fluid in the return conduit to move the valve head from the seat.
In order that the invention is more readily understood, embodiments thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS

FIG. 1 is a schematic fluid circuit diagram showing an overview of the system,

FIG. 2 is a fluid circuit diagram showing operation of the system of the invention,

FIG. 3 is a simple schematic showing electrical controls for the system of FIG. 2,

FIG. 4 is a schematic view indicating one modular refrigeration unit having supply and return header pipes for both the evaporator and condenser,

FIG. 5 is a detailed view of the supply and return header pipes and the servo valve of FIG. 3, and

FIG. 6 is a view similar to FIG. 4 but illustrating a different form of valve.

FIG. 7 is a schematic of the dedicated heat recovery chiller logic system.

FIG. 8 is a schematic illustrating the main elements of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The Dedicated Heat Recovery Chiller (DHRC) is designed to make use of the heat rejected in the condenser circuit of a refrigeration system to heat/preheat water for domestic and space heating use in applications such as showers, swimming pools, VAV reheat, or any other application requiring hot water. The DHRC is dependent upon the fact that there is an internal cooling requirement in the building. Typically this cooling requirement involves a chiller/air conditioner that would reject the heat in the condenser to the outside ambient by the structure of a water to refrigerant or air to refrigerant heat exchanger. This heat would typically be absorbed into the atmosphere and the energy would be wasted, where as a chiller utilizing the DHRC controls package can make the most of this energy and can help reduce the dependency of a water heater/boiler for the hot water requirements of the building.
HEAT OVERRIDE: If heat override is selected, the DHRC controls will stage the compressors ON and OFF based on the condenser water temperature and the heating mode control setpoints as configured in the System Variables. As the condenser water temperature drops below the control setpoint, more compressors will be called to run one at a time and this staging will continue to occur until all available compressors are ON and the chiller is at full load. If the condenser water temperature rises above the control setpoint, the compressors will be staged OFF and will continue to do so until all of the compressors in the system are OFF and the HEATING load is satisfied, This mode of operation bypasses the COOLING MODE setpoints and associated control logic.

Cool Override:

If cool override is selected, the DHRC controls will stage the compressors ON and OFF based on the evaporator water temperature and the cooling mode control setpoints as configured in the System Variables. As the evaporator water temperature rises above the control setpoint, more compressors will be called to run one at a time and this staging will continue to occur until all available compressors are ON and the chiller is at full load. If the evaporator water temperature drops below the control setpoint, the compressors will be staged OFF and will continue to do so until all of the compressors in the system are OFF and the COOLING load is satisfied. This mode of operation bypasses the HEATING MODE setpoints and associated control logic.
Referring to FIG. 1 there is illustrated a cooling system in which a plurality of refrigeration units 42 are used to chill water which is circulated through a chilled water circuit 40 by a circulating pump 41. The chilled water passes through loads 43, which may comprise cold water coils in an air conditioning system. The pump 41 is a variable speed pump and is located in the water supply line 8. Connected in parallel between the water supply line 8 and a return line 22 are evaporator heat exchangers 12 associated with each of the refrigeration units 42.
A condenser water circuit has a condenser water pump 14 which supplies water to condenser heat exchangers 16 which are connected in parallel across supply and return lines 17 and 18, respectively. The condenser water is circulated through a water tower 19 where it is cooled, in the usual manner, by airflow and evaporation.
Each refrigeration unit 42 includes at least one compressor 21 which circulates refrigerant through a refrigeration circuit 23 which incorporates an evaporator and a condenser.
A shut-off valve 24 is connected in each of the water return lines from each evaporator heat exchanger 12 and each condenser heat exchanger 16. The valves 24 may be of any suitable form, but in the embodiment illustrated, the valves are servo valves which are actuated by water under pressure bled from the respective evaporator water supply line 26 or condenser water supply line 20. The bleed water passes through a bleed pipe 27 and is controlled by a solenoid valve 28 actuated in conjunction with the respective compressor 21.
A pressure differential sensor 31 is associated with both the chilled water circuit 40 and the condenser water circuit 15 to sense the pressure differential between the respective water supply lines 8 and 17 and the return lines 22 and 18. The pressure differential sensors 31 provide a signal to respective motor speed controllers 32 which operate to vary the speed of the respective pumps 41 and 14 so as to maintain a predetermined pressure differential.
Referring to FIG. 2, a 3-phase power supply 33 is provided for the chilled water circulating pump 41 and the condenser water pump 14. Each motor speed controller 32 is an inverter which, in response to signals from the respective pressure differential sensors 31, varies the frequency of supply to the respective pumps to thereby vary the pump speed and, thus, the water flow in the respective circuits which, accordingly, varies the pressure differential between the respective supply and return lines 8 and 17, and 22 and 18, respectively.
The system also includes a control circuit incorporating a master controller 34 which controls operation of the refrigeration units 42 in accordance with a variety of factors including load demand, unit operating time, fault diagnosis, maintenance schedules and the like. In order to detect load changes, the temperature of the chilled water is measured in the supply line 8 and return line 22 by appropriate temperature measuring devices 36. Each compressor 21 is controlled by a compressor contactor 37 which receives a 24 volt power supply through an outstation controller 38. The outstation controller 38 receives control signals from the master controller 34 in response to sensed load conditions and predetermined system parameters. The solenoid valves 28 for each servo valve 24 on the respective units 42 are also controlled by the outstation controllers 38 such that if the compressor contactor 37 is actuated, the associated solenoid valves 28 are de-energized and, conversely, if a compressor contactor 37 is de-energized the associated solenoid valves 28 are energized.
On full load, each of the refrigeration units 42 is operating and chiller water flows through each of the evaporator heat exchangers 12. When the load decreases, the temperature of the chilled water in the chilled water supply and return lines 8 and 22 changes which initiates, through the master controller, operation of one of the outstation controllers 38 to deactivate a compressor 21. At the same time, the associated solenoid valves 28 are energized to thereby activate the shut-off valve 24 in the respective return lines 22 and 18 preventing water flow through the respective evaporator heat exchanger 12 and condenser heat exchanger 16. The pressure differential sensors 31 then detect a change in the pressure differential between the respective supply and return lines due to one or more of the heat exchangers being taken out of the water circuits. The pressure differential sensors 31 signal the respective motor speed controllers 32 to thereby vary the speed of the respective pumps 41 and 14 to decrease the pumping speed, the flow of water in the respective circuits and, thus, reduce the differential pressure to the predetermined value.
It will be seen that the combination of valves and variable speed pumps enables a substantial reduction in power consumed when the system is operating at less than full load. Further, by utilizing servo operated valves, the power requirements for such valve operations are minimal.
Referring to FIGS. 3 to 5, there is illustrated a modular refrigeration unit 42 which comprises a housing 112 mounting a pair of compressor units 114 which have parallel refrigeration paths 23 including evaporators and condensers. The evaporators are located in a common evaporator heat exchanger 12 while the condensers are located in a common condenser heat exchanger 16. The evaporator heat exchanger is used to chill water which flows from the supply header pipe 118 through the heat exchanger 12 and to the return header pipe 119. A supply conduit 121 connects the supply header pipe 118 to the evaporator heat exchanger 12 while a return conduit 122 connects with the return header pipe 119.
Similarly, water is supplied to the condenser heat exchanger 16 from the supply and return header pipes 123 and 124, respectively.
In an air conditioning system, a plurality of modular refrigeration units 42 are connected in parallel so that the chiller water and the condenser water circulates through each of the evaporator heat exchanger 12 and condenser heat exchanger 16 of each unit in the system. As previously indicated, the master controller 34 controls the number of refrigeration units 42 operating at any one time commensurate with the load on the system. The number of units operating to maintain the chiller water at the desired temperature is reduced when the load decreases and individual units are deactivated in accordance with such decreasing load requirements.
Similarly, as the load increases, the master controller 34 activates units as necessary to maintain the desired chiller water (or heating water) temperature.
When a modular unit 42 is deactivated, one or more valves are actuated to close off the supply and/or return of chiller and/or heating water to the evaporative heat exchanger 12 and condenser heat exchanger 16. In the embodiment illustrated in FIGS. 3 and 4, a valve 126 is provided in the return header pipe 119 to operate on the return conduit 122. A similar valve is provided in the condenser water return header pipe 124 to operate on the condenser return conduit 127.
The valve 126 consists of a pressure chamber 128 located on the outside of the header pipe 119, a valve stem 129 passing through a seal 131 in the return header pipe 119, a piston 132 on the end of the valve stem 129 in the pressure chamber, a valve head 133 on the other end of the valve stem 129, the valve head being of a size to close the opening to the return conduit 122. A pressure bleed pipe 134 runs from the supply header pipe 118 to the pressure chamber 128 to bleed supply fluid to the pressure chamber 128 and thus cause the piston 132 to move the valve head 133 into the sealing position, as shown in solid lines in FIG. 4. The pressure bleed pipe 134 is fitted with a normally closed, solenoid actuated valve 136 which closes the bleed pipe 134.
A similar valve arrangement is located on the condenser side of the modular unit 42.
In normal operation, when the modular refrigeration unit is in operation, and the compressors 114 are in operation, the solenoid is deactivated thus closing the pressure bleed pipe 134. The pressure of chiller water in the return conduit 122 and the return spring 120 is sufficient to force the valve head 133 away from the seat so that the return conduit 122 opens into the return header pipe 119 as shown in chain dot lines in FIG. 4. Similarly, the return header pipe on the condenser heat exchanger 117 is open and heat exchange fluid flows through both the evaporative and condenser heat exchangers 12 and 16.
When the modular refrigeration unit is deactivated, the solenoid valves 136 are actuated to open the bleed pipe 134 and fluid under pressure from the supply header pipes 118 and 123, respectively, operate the respective valves 126 so as to close off the respective return conduits 122 and 127. Thus, water no longer flows through the evaporative heat exchanger 12 and condenser heat exchanger 16. By taking these heat exchangers out of the respective water circuits, the loads on the circulating pumps are reduced accordingly thus enabling a reduction in pumping power by reducing pump speed.
As the solenoid actuated valves 136 operate only on fluid bleed lines 134, sealing difficulties are avoided and the valves 136 may be of relatively simple construction.
Referring to the embodiment illustrated in FIG. 5, instead of using valves of the type illustrated in FIGS. 3 and 4, this embodiment shows the use of two solenoid actuated butterfly valves 137 and 138 in each of the supply conduit 121 and return conduit 122. With this arrangement, the butterfly valves 137 and 138 are actuated to directly close off both the supply conduit 121 and return conduit 122 simultaneously. Such butterfly valves 137 and 138 are located directly in the respective conduits and may, if desired, be actuated by a single actuating solenoid. Alternatively, such valves may be pneumatically or hydraulically operated.
It will be appreciated that although the specific embodiments described use variable speed pumps for circulating the chiller water and condenser water, variable capacity pumps, or a combination of variable speed and capacity pumps may be used. Alternatively, staged pumps or even a plurality of pumps can be used for water circulation with one or more stages or individual pumps of a group being deactivated to reduce water flow as required by system changes.
Further, it will be appreciated that the condenser heat exchanger for each unit may utilize air cooling in which case the invention will be applicable to the chiller water side of the units. Conversely, the units may be used for heating purposes in which case the invention will be applicable particularly to the condenser water circuit.

Auto Control:

When AUTO CONTROL mode is selected, the DHRC controls package will monitor the water temperature in both the condenser and evaporator sides of the chiller and automatically determine the maximum load that the chiller can operate at any given time. The DHRC will initially start in the COOLING MODE of operation when “enabled” by the end user until the DHRC controls has the opportunity to better sense the cooling and heating load requirements in the system. The mode of operation that is automatically selected by the DHRC controller will be based on the pre-set System Variables that the end user configures for the heating and cooling requirements in their system.
For example: If we have a 100 ton chiller, and there is a 40 ton cooling load and a 60 ton heating load, the DHRC controls will be in “COOLING MODE” and will limit the 100 ton chiller to a maximum of 40 tons. This is necessary to prevent the evaporator from getting too cold, which could possibly cause safety trips or even damage to the chiller. If the conditions in the building change and the cooling demand increases to 80 tons but there is still only a 60 ton requirement for heating, then the DHRC controls will automatically switch to “HEATING MODE” and will limit the 100 ton chiller to a maximum of 60 tons (in this instance) to prevent the condenser from running too high in pressure/temperature. This logic will help prevent the DHRC from tripping on nuisance high pressure trips. When designed properly, the customer should be able to utilize the most out of there chiller and get the benefits of all of the reclaimed heat that would normally be rejected into the atmosphere.

Sequence of Operations

The Dedicated Heat Recovery Chiller (DHRC) shall be equipped with a microprocessor based return water controller. The DHRC shall have the capability to operate in response to either heating water or cooling water set points. The selection of these two modes of operation shall be made automatically by the DHRC's Master Controller. Alternatively, this mode may be set manually or through a binary input to the controller.

Heating Mode:

In Heating Mode the DHRC shall operate to provide maximum hot water to the building's systems while producing chilled water as a byproduct and thus reducing the load on the buildings main chiller system.
The DHRC will respond to the heating set points while in the Heating Mode. There shall be three set points which dictate the staging of compressors in this mode as follows:


	Heating Upper Set Point (HUSP)
	Heating Lower Set Point (HLSP)
	Variable Set Point (VSP)

The HUSP shall indicate the design leaving hot water temperature from the DHRC. The HLSP shall indicate the design entering hot water temperature at the DHRC. The VSP shall indicate a percentage between 0 and 80 which will allow for a leaving temperature reset based on entering hot water temperature. (That is, as the entering hot water temperature begins to rise, the DHRC's Master Controller may allow the leaving hot water temperature to fall at a corresponding rate to the VSP. For example, if the VSP is equal to 50%, then for every 1 degree F. rise in Entering Water Temperature—above the HLSP—the Leaving Water Temperature will be allowed to drop a corresponding 1 degree F. If the VSP is 0% then there will be no corresponding drop in Leaving Water Temperature on a rise in Entering Water Temperature. If the VSP is set at its maximum of 80% then for each 1 degree F. rise in Entering Water Temperature there will be a corresponding 4 degree F. drop in Leaving Water Temperature.
Any time the actual entering hot water temperature at the DHRC is below the HLSP the DHRC will operate at maximum capacity.
As the entering hot water temperature rises above the HLSP the DHRC will begin unloading compressor stages based on the setting of the HUSP and VSP to maintain set point.
The entering and leaving chilled water temperature will be monitored and any time any chilled water sensor reads 36° F. the corresponding portion of the DHRC will be locked-out on a freeze protection safety.

Cooling Mode:

In the Cooling Mode the DHRC shall operate to provide the required chilled water to the building's systems while producing hot water as a byproduct and thus reducing the load on the building's main boiler system.
The DHRC will respond to the cooling set points while in the Cooling Mode. There shall be three set points which dictate the staging of compressors in this mode as follows:
Cooling Upper Set Point (CUSP) Cooling Lower Set Point (CLSP) Variable Set Point (VSP)
The CUSP shall indicate the design entering chilled water temperature at the DHRC. The CLSP shall indicate the design leaving chilled water temperature from the DHRC. The VSP shall indicate a percentage between 0 and 80 which will allow for a leaving temperature reset based on entering chilled water temperature. (That is, as the entering chilled water temperature begins to drop, the DHRC's Master Controller may allow the leaving chilled water temperature to rise at a corresponding rate to the VSP. For example, if the VSP is equal to 50%, then for every 1 degree F. drop in Entering Water Temperature—below the CUSP—the Leaving Water Temperature will be allowed to rise a corresponding 1 degree F. If the VSP is 0% then there will be no corresponding rise in Leaving Water Temperature on a drop in Entering Water Temperature. If the VSP is set at its maximum of 80% then for each 1 degree F. drop in Entering Water Temperature there will be a corresponding 4 degree F. rise in Leaving Water Temperature.
Any time the actual entering chilled water temperature at the DHRC is above the CUSP the DHRC will operate at maximum capacity.
As the entering chilled water temperature drops below the CUSP the DHRC will begin unloading compressor stages based on the setting of the CLSP and VSP to maintain set point.
If at any time the entering and leaving water temperatures exceed the DHRC Design Envelope the corresponding portion of the DHRC will be locked out on a high compressor discharge pressure safety.

Automatic Changeover of Control:

At initiation of the system, the DHRC shall start in Heating Mode.
While in Heating Mode, if at any time the system senses that the cooling side of the load has fallen below set point, the system will automatically change over to Cooling Mode.
Similarly, while in Cooling Mode, if at any time the system senses that the heating side of the load has risen above set point, the system will automatically change over to Heating Mode.
The Automatic Changeover Controls will always respond to the smallest of the cooling and heating load. Therefore, the system will operate the maximum number available hours over its life thereby providing maximum economic benefit.
The Multistack Dedicated Heat Recovery Chiller was developed to eliminate the common practice (in many large commercial buildings) of operating electric water chillers for air conditioning while simultaneously operating a natural gas fired boiler for heating. There are over 100,000 commercial air conditioning water chillers installed in North America and in almost every case those buildings operate some kind of hot water boiler system (most commonly a natural gas burning boiler) in order to provide heat at the same time. During the summer months, this heat is often used for either Domestic Hot Water or Hot Water Reheat for summertime humidity control. Similarly, in the winter months when the prevailing requirement in many commercial buildings is for heating, there are internal building loads that require cooling. Therefore, in many commercial buildings there is simultaneous operation of both the air conditioning system and the heating system.
The DHRC Chiller, when properly applied, eliminates this simultaneous operation providing significant energy savings by reducing the operation of the boiler system (in some cases by as much as 65%). Since most hot water boilers make heat through the burning of natural gas, the significant reduction in Natural Gas Consumption offered by the DHRC not only saves utility costs, but also reduces the consumption of a limited natural resource. Furthermore, the most significant contributor to Global Warming is the burning of Fossil Fuels (like Natural Gas) which causes the emission Of C02, a Greenhouse Gas. Therefore, the DHRC has the potential to make a significant positive impact on the environment through the reduction in Greenhouse Gas Emissions in systems utilizing this technology.

Operation (See FIG. 1)

The Dedicated Heat Recovery Chiller (DHRC) is physically piped in parallel or in series with the main building's central chilled water and central hot water plants. These main heating and cooling plants remain an integral and vital part of the building. Often, the only purpose of the DHRC System is to monitor the operational temperatures of both of theses main systems and provide for any simultaneous requirement the building may have for cooling and heating.
For example, if there is a very large building cooling load and simultaneously there is a relatively small building heating load, the DHRC will provide all of the heat required by the building, eliminating any operation of the building's main heating system. At the same time the DHRC will provide cooling in a corresponding quantity to the heating it is providing to the building's heating loads. This cooling is supplied to the building cooling loads and the building's main chiller plant will simply provide less cooling than it would have in the absence of the DHRC. Essentially, the DHRC is pumping some of the heat generated by the building into the building's hot water system (instead of rejecting it to the atmosphere which is the more common practice) in order to eliminate boiler operation.
Similarly, if there is a very large building heating load and simultaneously there is a relatively small building cooling load, the DHRC will provide all of the cooling required by building, eliminating any operation of the building's main chiller system. At the same time the DHRC will produce heating in a corresponding quantity to the cooling it is providing to the building's cooling loads. This heating is supplied to the building's heating loads and the building's main heating plant will simply provide less heat than it would have in the absence of the DHRC. In this case the DHRC is pumping all of the heat generated by the building into the building's hot water system in order to eliminate chiller operation.
The DHRC uses the entering and leaving hot water and chilled water temperatures (Pipes A, B, C and D in FIG. 1) connected to the building's hot water and chilled water loads to determine its most efficient mode of operation. When it is initially enabled the DHRC will operate in Heating Control Mode. Once initial operation is established the DHRC will automatically change over from Heating Control Mode to Cooling Control Mode and vice versa based on its internal calculations on the most efficient mode of operation.
In the case of FIG. 1, the system temperatures are defined as follow:

Pipe A=Entering Hot Water

Pipe B=Leaving Hot Water

Pipe C=Entering Chilled Water

Pipe D=Leaving Chilled Water

The DHRC uses temperature sensors connected to each of the above pipes to monitor all four of these temperatures. It also has installed flow switches in each of the piping systems (that is, there is a proof of flow switch for both the hot water and chilled water systems to insure pumping operation is enabled). Proof of flow is critical because in the absence of chilled or hot water flow to the DHRC it is impossible for the DHRC to measure the water temperatures, and the corresponding load, in these systems.
On initial operation of the DHRC it will utilize the temperature sensed in Pipe A (Entering Hot Water Temperature), along with the programmed temperature set points within its electronic controller, to determine its operating point. The DHRC will have multiple stages of capacity control. That is, a typical DHRC will have between two and 24 steps of control. In a two-step machine, capacity will be capable of being controlled in the following steps: 0%, 50%, and 100%. In 24-step machine, capacity will be controlled as follows: 0%, 4%, 8%, 12%, 17%, 21%, 25%, 29%, 33%, 38%, 42%, 46%, 50%, 54%, 58%, 62%, 67%, 71%, 75%, 79%, 83%, 88%, 92%, 96%, and 100%. Each of these steps will have an identical affect on both total cooling and total heating output of the DHRC. That is, when the DHRC is operating at 50% of its capacity, it will be operating simultaneously at 50% of its total cooling capacity and 50% of its total heating capacity.

Heating Control Mode

When in heating control mode, a rise in the temperature in Pipe A indicates a reduction in the building's heating load requirement. Whenever the temperature in Pipe A is below the heating set point, the DHRC will operate at full capacity (100%). As the temperature in Pipe Arises, the DHRC will reduce its capacity from 100% to 0% corresponding to the temperature measured in Pipe A, the number of steps of control available in the DHRC, and the heating set points programmed into the DHRC.
The three heating mode set points that dictate the loading and unloading of the DHRC System while in heating mode are:

HUSP: Heating Upper Set Point

HLSP: Heating Lower Set Point

VSP: Variable Set Point

The HUSP represents the temperature in Pipe B when the DHRC is operating at its full capacity design point. The HLSP represents the temperature in Pipe A when the DHRC is operating at its full capacity design point. The VSP represents a percentage of reduction in Hot Water Temperature leaving the DHRC (Pipe B) that will be allowed when the DHRC is operating under part load conditions. Reducing the leaving hot water temperature from the DHRC under part load conditions is a common practice that allows for higher efficiency operation.
In order to determine the operational curve of the system, the DHRC's electronic controller calculates a temperature called the Heating No Load Point (HNLP). The formula for determining the Heating No Load Point is as follows for the Heating Mode:
HNLP=HUSP−(VSP*(HUSP−HLSP))
The DHRC then employs its available capacity controls to correlate the temperatures in Pipe A to a point between the HLSP and the HNLP.

Example 1

Heating Mode

HUSP=125° F.

HLSP=115° F.

VSP=50%

The Heating No Load Point (HNLP) is then calculated as follows:
HNLP=HUSP−(VSP*(HUSP−HLSP)=125° F.−(50%*(125° F.−115° F.)=120° F.
Therefore, in this case, the DHRC will operate its capacity controls based on temperature in Pipe A as it moves between the HLSP and the HNLP. That is, it will operate its capacity controls between measured temperatures of 115° F. and 120° F. in Pipe A. Any time the temperature in Pipe A is at or below the HLSP (115° F.), the DHRC will operate at 100% capacity. Any time the temperature in Pipe A at or above the HNLP (120° F. in this case), the DHRC will operate at 0% capacity. In between these two temperatures in Pipe A, there will be a linear relationship between capacity and temperature based on the DHRC's ability to step down. That is, if the DHRC has five-steps of capacity control (0%, 20%, 40%, 60%, 80%, and 100%). Then the following control logic will dictate DHRC loading:
Whenever the temperature in Pipe A is at or below the HLSP of 115° F. the DHRC will operate at 100% capacity
If the temperature in Pipe A is at 116° F. the DHRC will operate at 80% capacity
If the temperature in Pipe A is at 117° F. the DHRC will operate at 60% capacity
If the temperature in Pipe A is at 118° F. the DHRC will operate at 40% capacity
If the temperature in Pipe A is at 119° F. the DHRC will operate at 20% capacity
If the temperature in Pipe A is at or above 120° F. (the Heating No Load Point) the DHRC will operate at 0% capacity

Cooling Control Mode

The three cooling mode set points that dictate the loading and unloading of the DHRC System while in cooling mode are:

CUSP: Cooling Upper Set Point

CLSP: Cooling Lower Set Point

VSP: Variable Set Point

The CUSP represents the temperature in Pipe C when the DHRC is operating at its full capacity design point. The CLSP represents the temperature in Pipe D when the DHRC is operating at its full capacity design point. The VSP represents a percentage of rise in Chilled Water Temperature leaving the DHRC (Pipe D) that will be allowed when the DHRC is operating under part load conditions. Increasing the leaving chilled water temperature from the DHRC under part load conditions practice that allows for higher efficiency operation.
In order to determine the operational curve of the system, the DHRC's electronic controller calculates a temperature called the Cooling No Load Point (CNLP). The formula for determining the Cooling No Load Point is as follows for the Cooling Mode:
CNLP=CLSP+(VSP*(CUSP−CLSP))
The DHRC then employs its available capacity controls to correlate the temperature in Pipe C to a point between the CUSP and the CNLP.

Example 2

Cooling Mode

CUSP=55° F.

CLSP=45° F.

VSP=80%

The Cooling No Load Point (NLP) is then calculated as follows:
CNLP=CLSP+(VSP*(CUSP−CLSP)=45° F.+(80%*(55° F.−45° F.)=53° F.
Therefore, in this case, the DHRC will operate its capacity controls based on temperature in Pipe C as it moves between the CUSP and the CNLP. That is, it will operate its capacity controls between measured temperatures of 55° F. and 53° F. in Pipe C. Any time the temperature in Pipe C is at or above the CUSP (55° F.), the DHRC will operate at 100% capacity. Any time the temperature in Pipe C at or below the CNLP (53° F. in this case), the DHRC will operate at 0% capacity. In between these two temperatures in Pipe C, there will be a linear relationship between capacity and temperature based on the DHRC's ability to step down. That is, if the DHRC has four-steps of capacity control (0%, 25%, 50%, 75%, and 100%). Then the following control logic will dictate DHRC loading:
Whenever the temperature in Pipe C is at or above the CUSP of 55° F. the DHRC will operate at 100% capacity
If the temperature in Pipe C is at 54.5° F. the DHRC will operate at 75% capacity
If the temperature in Pipe C is at 54° F. the DHRC will operate at 50% capacity
If the temperature in Pipe C is at 53.5° F. the DHRC will operate at 25% capacity
If the temperature in Pipe C is at or below 53° F. the DHRC will operate at 0% capacity

Automatic Changeover of Control Point

As previously explained, when the DHRC initializes it will begin operation in the Heating Control Mode. Upon initialization, the DHRC will immediately calculate both the HNLP (Heating No Load Point) and the CNLP (Cooling No Load Point). It will perform capacity control based on the temperature in Pipe A and its Heating Control Mode Set Points (HUSP, HLSP, and VSP). It will also continually monitor the temperatures in Pipes B, C and D.
If while in the Heating Control Mode the DHRC senses that the temperature in Pipe C drops below the CNLP, the DHRC will perform a normal shut down and automatically restart in the Cooling Control Mode.
Similarly, if while in the Cooling Control Mode the DHRC senses that the temperature in Pipe A rises above the HNLP, the DHRC will perform a normal shut down and automatically restart in the Heating Control Mode.
It is essential that if the DHRC is to maximize its hours of operation, which maximizes its energy savings and positive environmental impact, that it must always use the smaller of the simultaneous loads (heating or cooling) as its point of control. If the DHRC were to operate from its Heating Mode controls in the absence of an adequate building cooling load it would eventually drive the building's cooling system temperatures so low that the DHRC system would freeze. Similarly, if the DHRC were to operate from its Cooling Mode controls in the absence of an adequate building heating load it would eventually drive the building's heating system temperatures so high that the DHRC system would overheat. The ability to automatically sense both the heating and cooling system loads through the monitoring of the temperatures in Pipes A and C coupled with the DHRC's ability to continually adjust its point of control between heating and cooling, in one embodiment, is critical to its successful operation.

Heat Pump Application

Master Control Requirements:

Two of the EX inputs may be modified for other purposes. EX1 will be modified so that when it is closed, the controller is in COOLING mode. EX3 will be modified so that when it is closed, the controller is in HEATING mode. if both inputs are open, the chiller is ‘DISABLED’. If both inputs are closed, the master control will be i_nHEATING Mode. Both of these inputs will not require a reset at the master control to resume operation. In addition, no fault will log in the FAULT REVIEW for these inputs. They will both be similar to EX2 input. The open line on the second status screen will display which mode the chiller is in, i.e. COOLING MODE I HEATING MODE.
Any time that the control changes from COOLING mode to HEATING mode all of the compressors will shut off. There will be a 30 second delay same as if the ON key was pressed and then a compressor will be allowed to start if there is a DEMAND present. The same will be true if we switch from HEATING mode to COOLING mode. This will make it obvious if the inputs for COOLING MODE/HEATING MODE are changing rapidly.
The other two EX inputs will act as they normally do. EX2 will be used for remote start/stop operations, and will not require a restart. EX4 will be used only for the Power Phase Monitor (PPM) system. This input will not require a restart of the chiller, but will log a fault in the FAULT REVIEW every time EX4 opens.
The Condenser Water temperature inputs (ECW and LCW) will not need to be able to read temperatures up to 150° F. The standard temperature range will be sufficient.
The Master Control may have separate Upper and Lower Setpoints for the Cooling Mode and the Heating Mode. The Cooling Mode setpoints will be the standard setpoints that are in every Master Control. The Heating Mode setpoints will be:


Variable	Range	Default

Upper Set Point (Heating)	80--120° F.	100° F.
Lower Set Point (Heating)	70--110° F.	90° F.

When the chiller is in COOLING MODE, the control of the compressors will be based off the ECHW (Entering Chilled Water) system sensor. As the ECHW temperature increases more compressors will be called to start. When the ECHW temperature decreases the compressors will unload.
When the chiller is in HEATING MODE, the control of the compressors will also use the ECHW (Entering Chilled Water) system sensor. As the ECHW temperature drops, more compressors will be called to start. When the ECHW temperature increases the compressors will unload.
How many compressors are running is based on the Upper and Lower Set Points for the individual mode of operation along with the VSP (Variable Set Point) value. For example, if the system variable were set as such:

Upper Set Point=55

Lower Set Point=45

VSP=50%

Upper Set Point (Heating)=120

Lower Set Point (Heating)=110

this would mean that in the COOLING MODE, ideally all of the compressors would be on when the ECHW temperature was 55° or above, and all of the compressors would be OFF when the ECHW temperature was 50° or below. When the controller was in the HEATING MODE, all of the compressors would be on when the ECHW temperature was 110° F. or below, and all of the compressors would be OFF when the ECHW temperature was 115° F. or above. There would also be an at-Jot mode in both the COOLING and HEATING modes.
Two sensor inputs may be added to the module boards. These two sensors may monitor the Leaving Condenser Water Temperature (LCW) of the two compressor circuits that are controlled by that module board. The code will incorporate a low temperature cutout on the Leaving Condenser Water Temperature. It will work exactly like the Leaving Chilled Water Temp. cutout (at 36° F., reset at 40° F.). This will be active in both the COOLING and HEATING modes of operation. The fault will need to display as LO LSW. The present low chilled water temperature display may be changed from LOCHW to LO LLW.
The System Condenser Water sensors will now become an active portion of the control. If the Leaving Condenser Water Temperature drops to 36.0° F. during operation, a LOW COMMON LSW TEMP SYSTEM fault will occur. Once the temperature rises to 40.0° F. the fault will change to a resetable fault. This fault will shut the entire system down, and a manual reset and restart will be required to resume operation.
All of the present cutouts on the module boards may remain as they are and may be active in both the COOLING and HEATING modes of operation. This may include the 36° F. cut out on individual LCHW Temp. and 25 or cut out on the SUCT. Temp. of each circuit.
In the Master Control, the CHW Flow Switch inputs may remain the same as in a standard unit. There is a 4 second delay on the chilled water flow switch input. If flow is not established in 4 seconds after the chiller is commanded ‘ON’ then the Master Control will lock the system out, on a fault and will require a manual reset and proof of flow at the controller before any compressors will be allowed to start. The chiller will be commanded ‘ON’ whenever EXI (HEATING MODE) or EX3 (COOLING MODE) is closed. If both inputs are open, the chiller will be commanded ‘OFF’, and the chilled water flow switch will not be monitored. This fault will display as “WAITING FOR LOAD WATER FLOW” instead of “WAITING FOR CHILLED WATER FLOW”.
On the condenser side, we need to change the input to respond the same as the CHW flow switch input. If flow is not established in 4 seconds after the chiller is commanded ‘ON’ then the Master Control will lock the system out on a fault and will require a manual reset and proof of flow at the controller before any compressors will be allowed to start. The chiller will be commanded ‘ON’ whenever EX1 (HEATING MODE) or EX3 (COOLING MODE) is closed. If both inputs are open, the chiller will be commanded ‘OFF’, and the chilled water flow switch will not be monitored. This fault will display as “WAITING FOR SINK/SOURCE WATER FLOW” instead of “WAITING FOR CONDENSER WATER FLOW
The Condenser Pump Relay Output may be disabled under certain conditions.
The following information may pertain to various screens and displays:
ECHW will display as ELW. LCHW will display as LLW. ECW will display as ESW. LCW will display as LSW.

Heat Pump Embodiment:

Master Control Requirements:

It may be possible to modify two of the EX inputs for other purposes.
EX1 will be modified so that when it is closed, the controller is in COOLING mode. EX3 will be modified so that when it is closed, the controller is in HEATING mode. if both inputs are open, the chiller is ‘DISABLED’. If both inputs are closed, the master control will be. in HEATING mode. Both of these inputs will not require a reset at the master control to resume operation. In addition, no fault will log in the FAULT REVIEW for these inputs. They will both be similar to EX2 input. The open line on the second status screen will display which mode the chiller is in (COOLING MODE/HEATING MODE).
Any time that the control changes from COOLING mode to HEATING mode all of the compressors will shut off. There will be a 30 second delay, same as if the ON key were to be pressed, and then a compressor will be allowed to start if there is a DEMAND present. The same will be true if there is a switch from HEATING mode to COOLING mode. This will make it obvious if the inputs for COOLING MODE/HEATING MODE are changing rapidly.
The other two EX inputs will act as they normally do. EX2 will be used for remote start/stop operations, and will not require a restart. EX4 will be used only for the Power Phase Monitor (PPM) supplied
by Multistack. This input will not require a restart of the chiller, but will log a fault in the FAULT REVIEW every time EX4 opens.
The Condenser Water temperature inputs (ECW and LCW) will not need to be able to read temperatures up to 150° F. The standard temperature range will be sufficient.
The Master Control will have separate Upper and Lower Setpoints for the Cooling Mode and the Heating Mode. The Cooling Mode setpoints will be the standard setpoints that are in every Master Control. The Heating Mode setpoints will be:

Variable Range Default Upper Set Point (Heating) 80-120° F. 100° F. Lower Set Point (Heating) 70-110° F. 90° F.

When the chiller is in COOLING MODE, the control of the compressors will be based off the ECHW (Entering Chilled Water) system sensor. As the ECHW temperature increases more compressors will be called to start. When the ECHW temperature decreases the compressors will unload.
When the chiller is in HEATING MODE, the control of the compressors will also use the ECHW (Entering Chilled Water) system sensor. As the ECHW temperature drops, more compressors will be called to start. When the ECHW temperature increases the compressors will unload.
How many compressors are- running is based on the Upper and Lower Set Points for the individual mode of operation along with the VSP (Variable Set Point) value. For example, if the system variable were set as such:

Upper Set Point 55

Lower Set Point=45

VSP=50%

Upper Set Point (Heating)=120

Lower Set Point (Heating)=110

this would mean that in the COOLING MODE, ideally all of the compressors would be on when the ECHW temperature was 55. ° F. or above, and all of the compressors would be OFF when the ECHW temperature was 50° F. or below. When the controller was in the HEATING MODE, all of the compressors would be on when the ECHW temperature was 110° F. or below, and all of the
compressors would be OFF when the ECHW temperature was 115° F. or above. There would also be an abort mode in both the COOLING and HEATING modes.
It may be desirable to add two sensor inputs to the module boards. These two sensors will monitor the Leaving Condenser Water Temperature (LCW) of the two compressor circuits that are controlled by that module board. The code will have to encorporate a low temperature cutout on the Leaving Condenser Water Temperature. It will need to work exactly like the Leaving Chilled Water Temp. cutout (at 36° F., reset at 40° F.). This will be active in both the COOLING and HEATING modes of operation. The fault will need to display as LO LSW. The present low chilled water temperature display may be changed from LOCHW to LO LLW.
The System Condenser Water sensors will now become an active portion of the control. If the Leaving Condenser Water Temperature drops to 36.0° F. during operation, a LOW COMMON LSW TEMP SYSTEM fault will occur. Once the temperature rises to 40.0° F. the fault will change to a resetable fault. This fault will shut the entire system down, and a manual reset and restart will be required to resume operation.
All of the present cutouts on the module boards will remain as they are and will be active in both the COOLING and HEATING modes of operation. This will include the 36° F. cut out on individual LCHW
In the Master Control, the CHW Flow Switch inputs will remain the same as in a standard unit. There is a 4 second delay on the chilled water flow switch input. If flow is not established in 4 seconds after
the chiller is commanded ‘ON’ then the Master Control will lock the system out on a fault and will require a manual reset and proof of flow at the controller before any compressors will be allowed to start. The chiller will be commanded ‘ON’ whenever EXI (HEATING MODE) or EX3 (COOLING MODE) is closed. If both inputs are open, the chiller will be commanded ‘OFF’, and the chilled water flow switch will not be monitored. This fault will display as “WAITING FOR LOAD WATER FLOW” instead of “WAITING FOR CHILLED WATER FLOW”.
On the condenser side, it may be desirable to change the input to respond the same as the CHW flow switch input. If flow is not established in 4 seconds after the chiller is commanded ‘ON’ then the Master Control will lock the system out on a fault and will require a manual. reset and proof of flow at the controller before any compressors will be allowed to start. The chiller will be commanded ‘ON’ whenever EX! (HEATING MODE) or EX3 (COOLING:̂,ODE) is closed. If both inputs are open, the chiller will be commanded ‘OFF’, and the chilled water flow switch will not be monitored. This fault will display as “WAITING FOR SINK/SOURCE WATER FLOW” instead of “WAITING FOR CONDENSER WATER FLOW”.

Disable the Condenser Pump Relay Output.

The following information will pertain to ALL screens and displays:
ECHW will display as ELW. LCHW will display as LLW. ECW will display as ESW. LCW will display as LSW.

Master Control Requirements:

In one embodiment, there must be a modification of two of the EX inputs for other purposes.
EX1 will be modified so that when it is closed, the controller is in COOLING (Summer) mode. EX3 will be modified so that when it is closed, the controller is in HEATING (Winter) mode. If both inputs are open, the chiller is commanded ‘OFF’. If both inputs are closed, the master control will be in HEATING (Winter) mode. Both of these inputs will not require a reset at the master control to resume operation. In addition, no fault will log in the FAULT REVIEW for these inputs. They will both be similar to EX2 input. The open line on the second status screen will display which mode the chiller is in (COOLING MODE/HEATING MODE).
Any time that the control changes from COOLING mode to HEATING mode all of the compressors will shut off. There will be a 30 second delay, same as if the ON key were to be pressed, and then a compressor will be allowed to start if there is a DEMAND present. The same will be true if there is a switch from HEATING mode to COOLING mode. This will make it obvious if the inputs for COOLING MODE/HEATING MODE are changing rapidly.
The other two EX inputs will act as the normally do. EX2 will be used for remote start/stop operations, and will not require a restart. EX4 will be used only for the Power Phase Monitor (PPM) supplied by Multistack. This input will not require a restart of the chiller, but will log a fault in the FAULT REVIEW every time EX4 opens.
The Condenser Water temperature inputs (ECW and LCW) will need to be able to read temperatures up to 150° F. The FAULT REVIEW will also need to log these temperatures properly in the case of a fault. This will require a special Master Control with modified inputs for these two sensors.
The Master Control will have separate Upper and Lower Setpoints for the Cooling Mode and the Heating Mode. The Cooling Mode setpoints will be the standard setpoints that are in every Master Control. The Heating Mode setpoints will be:


Variable	Range	Default

Upper Set Point (Heating)	110--140° F.	125° F.
Lower Set Point (Heating)	100--130° F.	115° F.

When the chiller is in COOLING MODE, the control of the compressors will be based off the ECHW (Entering Chilled Water) system sensor. As the ECHW temperature increases more compressors will be called to start. When the ECHW temperature decreases the compressors will unload.
When the chiller is in HEATING MODE, the control of the compressors will change over to the ECW (Entering Condenser Water) system sensor. As the ECW temperature drops, more compressors will be called to start. When the ECW temperature increases the compressors will unload.
How many compressors are running is based on the Upper and Lower Set Points for the individual mode of operation along with the VSP (Variable Set Point) value. For example, if the system variable were set as such:

Upper Set Point=55

Lower Set Point=45

VSP=50%

Upper Set Point (Heating)=125

Lower Set Point (Heating)=115

this would mean that in the COOLING MODE, ideally all of the compressors would be on when the ECHW temperature was 55° F. or above, and all of the compressors would be OFF when the ECHW temperature was 50° F. or below. When the controller was in the HEATING MODE, all of the compressors would be on when the ECW temperature was 115° F. or below, and all of the compressors would be OFF when the ECW temperature was 120° F. or above. There
would also be an abort mode in both the COOLING and HEATING modes.
All of the present cutouts on the module boards will remain as they are and will be active in both the COOLING and HEATING modes of operation. This will include the 36° F. cut out on individual LCHW Temp. and 25° F. cut out on the SUCT. Temp. of each circuit.
In the Master Control, the Flow Switch inputs will remain the same as our standard unit. There is a 4 second delay on the chilled water flow switch input. If flow is not established in 4 seconds after the chiller is commanded ‘ON’ then the Master Control will lock the system out on a fault and will require a manual reset and proof of flow at the controller before any compressors will be allowed to start. The chiller will be commanded ‘ON’ whenever EXI (SUMMER/HEATING MODE) or EX3 (WINTER/COOLING MODE) is closed. If both inputs are open, the chiller will be commanded ‘OFF, and the chilled water flow switch will not be monitored.
On the condenser side, it is not important to monitor the flow switch input until a compressor starts. If flow is not established in 10 seconds after the compressor starts, then the Master Control will lock the system out on a fault and will require a manual reset and proof of flow at the controller before any compressors will be allowed to start. Any time after the 10 second delay after the first compressor starts there will be only a 4 second delay for this fault.
The customer would also like a dry contact from a relay for the ALARM OUTPUT of the Master Control. A relay may be added that will use the standard Customer Alarm Relay (24V) output on the Master Control. No changes will be required for this request.

Other Requirements:

The individual circuits high pressure switches will be set at 365-370 PSIG which corresponds to a temperature of about 146-150° F. on the condenser side. The will be required because the chiller must operate at 125° F. condenser entering water temperature (ECW).
This design does not fall within the scope of our approval agency requirements, and such we will not be able to label it ETL approved.
In one embodiment, the HRC (Heat Recovery Chiller) will utilize one input (EX2) for chiller control. EX2 must be closed for the chiller to operate regardless of the CONTROL MODE. This will eliminate the use of EX1 and EX3 for determining what mode the controller should be in. EX1 and EX3 will default back to their previous configuration.
A SYSTEM VARIABLE may be added that has the options of HEAT OVERRIDE, COOL OVERRIDE, and AUTO CONTROL. This variable will be called CONTROL MODE.

- If HEAT OVERRIDE is selected, the control will act as it did when EX3 was closed.
- If COOL OVERRIDE is selected, the control will act as it did when EX1 was closed and EX3 was open.
- If AUTO CONTROL is selected, then control to the following set of parameters.

Any time the HRC is started (EX2 closed or On/Off button pushed) it will initially go into “Cooling” control mode.

While the HRC is in “Cooling” Control Mode:

If the entering heating water temperature (ECW) rises above the no-load point (default 120° F.) of the Heating Mode, then the controls will do an automatic change-over to “Heating” control. This will cause all of the compressors to turn Off, and start a 30 second count down to start. The control will now display Heating Mode information.

While the HRC is in “Heating” Control Mode:

If the entering cooling water temperature (ECHW) drops below the no-load point (default 50° F.) of the Cooling Mode, then the controls will do an automatic change-over to “Cooling” control. This will cause all of the compressors to turn Off, and start a 30 second count down to start. The control will now display Cooling Mode information.
In the case that the ECW is above the no load point of Heating Mode, and the ECHW is below the no load point of Cooling Mode everything should be OFF and the controller would be in Cooling. Mode.

- It may be necessary to modify the CPR output. This output will need to be energized as soon as EX2 closes, or any time the Chiller is Commanded ON instead of when a compressor starts. This will occur in all modes of operation. There should be a 10 second delay after the start of the pump before a fault condition can occur, and 4 seconds any time thereafter. Manual reset and restart of chiller may be necessary to resume operation. You will need to remove the portion of code that requires proof of flow in order to reset this fault.
- It may be possible to add one SYSTEM FAULT to the control. HIGH ECW TEMP. This fault would occur if the ECW reached 150° F. If this fault occurs, command the chiller OFF. This will turn all of the compressors OFF as well as the CPR output. Manual reset and restart may be necessary to resume operation.

In one embodiment, the need for an external signal to tell what mode the system is operating in could be eliminated.

Heat Recovery Chiller Auto-Changeover Controls

When the HRC is in “Cooling” Control Mode:

If the entering heating water temperature drops below the no-load point, then the controls will
change-over to “Heating” control

When the HRC is in “Heating” Control Mode:

If the entering cooling water temperature drops below the no-load point, then the controls will
change-over to “Cooling” control
The HRC will be utilize EX2 for remote start/stop. Any time the HRC is started it will initially go into “Cooling” control.

Specific Applications:

70/90 Ton Heat Recovery Controls

External Inputs: (EX Inputs)

The customer inputs (EX Inputs) will not need to be modified for this program. EX1 and EX3 will be closed circuit to operate, open to stop. These two inputs would require manual resets to resume operation. EX2 would be utilized as the Customers Remote Start/Stop contact. Open to stop operation, closed to start the chiller. No reset required to resume operation. EX4 will be used for the PPM input (Power Phase Monitor).

System Variables:

The System Variables may be expanded to encorporate a COOL MODE and HEAT MODE set of variables for the following: UPSETPT, LOSETPT VSP VALUE, T-DIFF. The COOL MODE setpoints will be the same as in all 70/90 Ton standard program chips. Which are:


Variable	Range	Default

Upper Set Point (Cooling)	45-80° F.	125° F.
Lower Set Point (Cooling)	35-70° F.	115° F.
VSP VALUE	0-80%	50
T-DIFF	15-210 Secs.	90 Secs.

The HEAT MODE setpoints will need to be adjustable as follows:


Variable	Range	Default

Upper Set Point (Heating)	110-130° F.	125° F.
Lower Set Point (Heating)	100-120° F.	115° F.
VSP VALUE	0-80%	50
T-DIFF	15-210 Secs.	90 Secs.

There may also be an additional System Variable called CONTROL MODE. The options for this variable will be: HEAT OVERRIDE, COOL OVERRIDE, and AUTO CONTROL. This point may be able to be written to by a BAS controller through the RS232 port.

Status Screens:

Move the display of current faults from the first screen to the second status screen (center bottom). Replace the current faults on the first (main) status screen with the display of the mode of operation of the chiller. (HEATING or COOLING)
The condenser water temperature inputs (ECW and LCW) may be able to read temperatures up to 150° F. The FAULT REVIEW will also need to log these temperatures properly in the case of a fault. This will require the use of a special Master Control with modified inputs for these two sensors.

Oct. 6, 2003

Logic of Operation:

Anytime the HRC (Heat Recovery Chiller) is started (EX2 closed or On/Off button pushed) it will initially go into “Cooling” control mode. There will be a 30 second countdown to start before any compressor will start. Also, ideally anytime the controller changes from one mode to another, there should be a 30 second count before any compressor will be allowed to start.

While the HRC is in “Cooling Control Mode:

If the entering condenser water temperature (ECW) rises above the no-load point (default 120° F.) of the Heating Mode, then the controls will do an automatic change-over to “Heating” control. This will cause all of the compressors to turn Off, and start a 30 second count down to start. The control will now display Heating Mode information.

While the HRC is in “Heating” Control Mode:

If the entering chilled water temperature (ECHW) drops below the no-load point (default 50° F.) of the Cooling Mode, then the controls will do an automatic change-over to “Cooling” control. This will cause tall of the compressors to turn Off and start a 30 second count down to start. The control will now display Cooling Mode information.
In the case that the ECW is above the no load point of Heating Mode and the ECHW is below the no load point of Cooling Mode, everything should be OFF, and the controller would be in Cooling Mode.
How many compressors are running is based on the Upper and Lower Set Points for the individual mode of operation along with the VSP (Variable Set Point) value. For example, if the System Variables were set as such:

Upper Set Point (Cooling)=55 Lower Set Point (Cooling)=45 VSP (Cooling)=50 Upper Set Point (Heating)=125 Lower Set Point (Heating)=115

VSP (Heating)=50

This would mean that in the “Cooling” mode of operation, ideally all of the available compressors would be on when the ECHW temperature was 55° F. or above, and all of the compressors would be OFF when the ECHW temperature was 50° F. or below. When the controller was in the “Heating” mode of operation, all of the compressors would be on when the ECW temperature was 115° F. or below, and all of the compressors would be OFF when the ECW temperature was 120° F. or above. There would also be an abort mode in both the Cooling and Heating modes of operation similar to the standard program.
It would also be possible to modify the CPR output so that it is energized as soon as EX2 closes (or anytime the Chiller is commanded ON) instead of when a compressor starts. This should occur in all modes of operation. There should be a 10 second delay after the start of this CPR output before a CW FLOW fault can occur. Any time after the initial 10 seconds, if the CW FLOW input (TB11-pin 9) is open for 4 seconds, a CW FLOW fault will occur. Manual reset and restart of chiller may be required to resume operation. It may be necessary to remove the portion of the code that requires proof of flow in order to reset this fault.
An additional SYSTEM fault may be added to the control logic. Its name is HIGH ECW TEMP. This fault would occur if the ECW temperature reached 140° F. If this fault occurs, command the chiller OFF. This will turn all of the compressors OFF as well as the CPR output. Manual reset and restart may be required to resume operation.

Oct. 6, 2003

All other safeties from the module boards will remain as they are and will be active in both the COOLING and HEATING modes of operation. This will include the 36° F. cut out on individual LCHW Temp. and 25° F. cut out on the SUCT. Temp. of each circuit.

Other Requirements:

The individual circuits high pressure switches will need to be set to 330 psig, which corresponds to a temperature of about 138° F. on the condenser side. The rated load amps for the compressors will be preliminarily set as:

RLA's

	208 V	230 V	460 V	575 V

70 TON	219 amps	198 amps	99 amps	80 amps
90 TON	297 amps	268 amps	134 amps	108 amps

OCT. 6, 2003

The system may also include the following features.
A heating and/or cooling system comprising at least one modular dedicated heat recovery refrigeration units each of which has at least one compressor, an evaporator heat exchanger and a condenser heat exchanger, supply and return fluid conduit on each unit for conveying a heat exchange fluid through the evaporator heat exchanger, said supply and return fluid conduit being connected to respective supply and return manifold so that the evaporator heat exchangers of the system are connected in parallel across the manifold, pump disposed in said manifold for circulating the heat exchange fluid through the manifold, said pump including pump control to vary the flow of said heat exchange fluid, and valve associated with each unit to selectively close at least one of the supply and return fluid conduit.
The system may include differential pressure sensing structure to sense the pressure differential between the supply and return manifold, said pump control being responsive to said sensing structure to vary the flow of said heat exchange fluid to maintain a predetermined pressure differential.
The system may include a master controller to monitor system operating parameters and control the modular units, the pump and each valve, said master controller receiving signals from temperature sensors in the supply and return manifold, compressor contactors for each compressor which are activated or deactivated by the master controller in response to manifold temperatures, and structure to operate the valve structure of those units which are deactivated to close the respective supply and/or return fluid conduit structure.
The system may have a master controller which activates or deactivates selected compressor structure in response to manifold temperatures and so that all units operate substantially equally.
The system may have a valve structure mounted on each unit so as to selectively close only the return fluid conduit structure.
The system may have a valve structure mounted on each unit so as to selectively close only the return fluid conduit structure.
The system may have a valve structure which are mounted on each unit so as to selectively close only the return fluid conduit structure.
The system may have second supply and return conduit conveying condenser fluid to the condenser heat exchanger of each unit, said second conduit being connected to condenser fluid manifolds which are interconnected so that the condenser heat exchangers are connected in parallel, second pump for circulating said condenser fluid, said second pump having second pump control structure to vary the flow of said condenser fluid, and condenser valve structure to selectively close at least one of the second supply and return conduit on each unit.
The system may have valve structure comprising a servo valve having a valve head movable to substantially seal against a valve seat in the respective return fluid conduit, a piston connected to the valve head, a pressure line to convey fluid from the supply manifold to said piston, and closure structure to selectively close the pressure line.
The system may have closure structure comprising an inline solenoid valve in the pressure line.
The system may have a solenoid valve which is a normally closed valve which opens the pressure line when energised.
The system may have an outstation controller which switches a supply voltage to either the solenoid valve or compressor contactor in response to the presence or absence of a control signal for actuation of the respective compressor.
The system may have pump control structure comprising motor speed controller structure to vary the speed of said pump.
The system may have a condenser heat exchanger which is an air-cooled heat exchanger.
The dedicated heat recovery air conditioning system according to the present invention may include a plurality of modular refrigeration units each having at least one compressor in a refrigeration circuit which includes an evaporator and a condenser, a chiller water circuit including water supply and return manifold pipes and a water circulating pump, a motor speed controller to control the speed of the pump motor, a pressure differential sensor to sense the water pressure difference between the supply and return manifold pipes, differential signal to supply a control signal to the motor speed controller in response to a predetermined sensed pressure differential, a chiller water supply and return conduit for each evaporator to convey water from the chiller water circuit to a heat exchanger associated with the evaporator such that the heat exchangers are connected in parallel, a valve in at least one of each supply and return conduit, and valve actuating structure to close the valves when the respective at least one compressor is deactivated.
The system may have a valve which is a servo valve actuated by supply manifold water through a bleed pipe and controlled by a solenoid valve in the bleed pipe.
The system may have a temperature measuring device which measures the temperature of the water in the supply and return manifold pipes, and a master controller activates or deactivates compressors of the system in response to measured temperatures and pre-programmed instructions to effect a decrease or increase, respectively, of the temperatures and, at the same time deactivates or activates, respectively, the valve actuating structure.
The present invention may include a heating and/or cooling system comprising a plurality of modular refrigeration units each of which has at least one compressor, an evaporator heat exchanger and a condenser heat exchanger, supply and return fluid conduit being connected to respective supply and return manifold so that the evaporator heat exchangers of the system are connected in parallel across the manifold, pump for circulating the heat exchange fluid through the manifold, said pump including pump control structure to vary the flow of said heat exchange fluid, valve structure associated with each unit to selectively close at least one of the supply and return fluid conduit, second supply and return conduit structure conveying condenser fluid to the condenser heat exchanger of each unit, said second conduit being connected to condenser fluid manifolds which are interconnected so that the condenser heat exchangers are connected in parallel, second pump for circulating said condenser fluid, said second pump having second pump control to vary the flow of said condenser fluid, and condenser valve to selectively close at least one of the second supply and return conduit on each unit.
The system may include second pump control which includes a condenser fluid pressure differential sensor to sense the pressure differential between the condenser fluid supply manifold and return manifold, and is responsive to the sensor to vary the flow of condenser fluid to maintain a predetermined pressure differential.
The system may function such that condenser fluid is circulated through a cooling tower.
The present invention may include a heating and/or cooling system comprising at least one modular dedicated heat recovery refrigeration unit each of which has at least one compressor, an evaporator heat exchanger and a condenser heat exchanger supply and return fluid conduit on each unit for conveying a heat exchange fluid through the evaporator heat exchanger, said supply and return fluid conduit being connected to respective supply and return manifold so that the evaporator heat exchangers of the system are connected in parallel across the manifold, pump for circulating the heat exchange fluid through the manifold, said pump including pump control to vary the flow of said heat exchange fluid, valve associated with each unit to selectively close at least one of the supply and return fluid conduit, and differential pressure sensing structure to sense the pressure differential between the supply and return manifold, said pump control structure being responsive to said sensing structure to vary the flow of said heat exchange fluid to maintain a predetermined pressure differential.
The system may include a master controller to monitor system operating parameters and control the modular units, the pump and each valve, said master controller receiving signals from temperature sensors in the supply and return manifold, compressor contactors for each compressor which are activated or deactivated by the master controller in response to manifold temperatures, and structure to operate the valve of those units which are deactivated to close the respective supply and/or return fluid conduit.
The system may include valve which are mounted on each unit so as to selectively close only the return fluid conduit.
The present invention may include a heating and/or cooling system comprising at least one modular dedicated heat recovery refrigeration unit each of which has at least one compressor, an evaporator heat exchanger and a condenser heat exchanger, supply and return fluid conduit on each unit for conveying a heat exchange fluid through the evaporator heat exchanger, said supply and return fluid conduit being connected to respective supply and return manifold so that the evaporator heat exchangers of the system are connected in parallel across the manifold, pump for circulating the heat exchange fluid through the manifold, said pump including pump control to vary the flow of said heat exchange fluid, valve associated with each unit to selectively close said return fluid conduit, a master controller to monitor system operating parameters and control the modular units, the pump and each valve, said master controller receiving signals from temperature sensors in the supply and return manifold, compressor contactors for each compressor which are activated or deactivated by the master controller in response to manifold temperatures, and structure to operate the valve of those units which are deactivated to close the respective supply and/or return fluid conduit.
The present invention may include a heating and/or cooling system comprising at least one modular dedicated heat recovery refrigeration units each of which has at least one compressor, an evaporator heat exchanger and a condenser heat exchanger, supply and return fluid conduit on each unit for conveying a heat exchange fluid through the evaporator heat exchanger, said supply and return fluid conduit being connected to respective supply and return manifold, so that the evaporator heat exchangers of the system are connected in parallel across the manifold, pump for circulating the heat exchange fluid through the manifold, said pump including pump control structure to vary the flow of said heat exchange fluid, valve associated with each unit to selectively close said supply fluid conduit, a master controller to monitor system operating parameters and control the modular units, the pump and each valve, said master controller receiving signals from the temperature sensors in the supply and return manifold, compressor contactors for each compressor which are activated or deactivated by the master controller in response to manifold temperatures, structure to operate the valve of those units which are deactivated to close the respective supply and/or return fluid conduit, wherein said master controller is arranged and constructed to activate or deactivate selected compressor in response to manifold temperatures so that all units operate substantially equally.
The present invention may include a heating and/or cooling system comprising at least one modular dedicated heat recovery refrigeration units each of which has at least one compressor, an evaporator heat exchanger and a condenser heat exchanger, supply and return fluid conduit on each unit for conveying a heat exchange fluid through the evaporator heat exchanger, said supply and return fluid conduit being connected to respective supply and return manifold so that the evaporator heat exchangers of the system are connected in parallel across the manifold, pump for circulating the heat exchange fluid through the manifold, said pump including pump control to vary the flow of said heat exchange fluid, valve associated with each unit to selectively close at least one of the supply and return fluid conduit, said valve comprising a servo valve having a valve head movable to substantially seal against a valve seat in the respective return fluid conduit, a piston connected to the valve head, a pressure line to convey fluid from the supply manifold to said piston, and closure structure arranged and constructed to selectively close the pressure line, said closure structure comprising an inline solenoid valve in the pressure line, wherein an outstation controller switches a supply voltage to either the solenoid valve or compressor contactor in response to the pressure or absence of a control signal for actuation of the respective compressor.
The dedicated heat recovery chiller sensor monitors both sides, heating and cooling. The dedicate heat recovery chiller reacts to the smaller demand. The result is no wasted heat and no wasted cooling. The dedicated heat recovery chiller acts to control the load which is smaller. In the present invention, all of the otherwise wasted heat is used to supply the heat input for the main building heating supply. The overall effect is to reduce the outside energy needed to create the correct temperature hot water for the building heating input circuit by preheating the input water to the main boiler.
The dedicated heat recovery chiller is sized to run at full load all year. The dedicated heat recovery chiller supplies all heat requirements to the building in the summer while cooling at the same time and also may be sized to substitute all cooling load in the winter. In one embodiment, the dedicated heat recovery chiller is sized to the larger of either the entire summer heating load or the entire winter cooling load. The dedicated heat recovery chiller acts to pre-cool the main chiller water and to preheat the main boiler water.
The sensor senses and controls based upon the return water line characteristics from the building to the main heating unit, and the cooled condenser water line in the dedicated heat recovery chiller.

Claims

1. A dedicated heat recovery chiller, comprising:

a modular dedicated heat recovery chiller,

a sensor,

a dedicated heat recovery chiller evaporator waste heat line exiting the dedicated heat recovery chiller,

a dedicated heat recovery chiller condenser coolant line entering the dedicated heat recovery chiller,

a dedicated heat recovery chiller chilled water line,

a dedicated heat recovery chiller return water line,

a connection on the dedicated heat recovery chiller condenser line for exchanging heat from a main heating unit return water line,

a connection on the dedicated heat recovery chiller evaporator line for exchanging heat with a main heating unit return water line,

a connection on the dedicated heat recovery chiller chilled water line for exchanging heat with a return water line to a main chiller unit,

a connection on the dedicated heat recovery chiller return water line for exchanging heat with a return water line to a main chiller unit,

wherein the dedicated heat recovery chiller supplies heat to the return water line to preheat return water to the main heating unit,

the sensor sensing the return water line to the main heating unit and the dedicated heat recovery chiller condenser coolant line entering the dedicated heat recovery chiller.