AU776392B2 - Air control system for an air-conditioning installation - Google Patents

Description

AIR CONTROL SYSTEM FOR AN AIR-CONDITIONING INSTALLATION Field of the Invention The invention relates to air-conditioning, heating and cooling systems and industry gas heating systems, and in particular to control systems for controlling temperature and air-flow from an air-conditioning unit to a multiple of zones in a domestic environment.

Background of the Invention Within the Australian domestic market, air-conditioning installations generally comprise an- air-conditioning unit, whose fan and compressor are controlled by a unit control system, and various collection and distribution apparatus.

For an air conditioning installation within a house, air is generally drawn in to the air-conditioning unit via a return air grille which is located centrally within the house. Adjacent the return air grille of the unit will be located a temperature transducer from which will be received data relating to the "average" temperature within the house. The unit control system reads this average temperature, and the set point determined by the occupant, then uses this data to determine the fan speed and operation of the compressor.

o In a basic form, the air-conditioning unit may service two zones, and will be designed to have a capacity to provide sufficient air to the largest of these zones.

Thus the air-conditioning unit is limited in capacity to service one zone at a time.

Generally the zones are established on the basis of day and night cycles in that one zone may provide air for the bedrooms and the other zone to provide air to the day time living spaces.

25 The unit is connected to each zone via connecting ducts which will have in series, an intermediate diverter and a terminal air diffuser located within the designated zone. So, in switching between one zone and the other, it is a matter opening the diverter of one zone and closing the other.

In more elaborate installations there can be multiple zones serviced by the air-conditioning unit, the zones being notionally divided between the rooms, such as for bedrooms, family room, kitchen, study, and infrequently used areas, such as for formal entertaining. Again the air-conditioning unit is designed to service a limited combination of zones, but it may be that on certain occasions the unit will have to provide for either larger or smaller zone combinations than the unit was selected for.

As stated, to provide a sufficient volume of air in most circumstances, the air-conditioning unit will be designed to service a pre-determined combination of zones. Thus, when the air-conditioning unit is switched to servicing a combination of zones requiring a lower capacity than the designated zone combination, said zone will be over cooled or heated. Nothing within such a conventional system provides for selectively varying the volume of air going to a particular zone, and so the possibility that one or more zones may never be adequately serviced exists for conventional installations.

To overcome some of these short comings it is normal at the time of installing of the air-conditioning installation to balance the house by permanently fixing diverters, or dampers, for those zones of less capacity than the largest so that when the air-conditioning unit has its air-flow diverted to the smaller zone the added resistance ensures a proportional air-flow to the smaller zone.

Problems arise in this case when one considers that on any given day the relevant ambient temperatures between zones can vary depending on the position of the sun, whether or not curtains are drawn, the time of year etc. Thus, 20 each variable tends to vary the relative capacities of zones and thus often makes the balancing procedure superfluous. If under ideal conditions, the night cycle zone requires 10% less air-flow in order to achieve the same temperature as the day time cycle zone, then the diverter or damper, can be proportionally opened or closed to accommodate this lesser requirement for air-flow. However, outside ideal conditions, that is, on extremely cold or extremely hot evenings, the bedrooms will require much greater or much less air-flow in order to achieve the desired temperature. However, as the temperature transducer is located adjacent the return air grille, then temperature input to the unit control system is based on an average temperature of the total house. Thus, if the bedrooms are extremely hot and the living room extremely cold, the unit control system will interpret this as being an ideal condition, and thus operate the air-conditioning unit accordingly. It follows that the majority of time it is possible for no zone to be controlled at the desired temperature.

Statement of Invention It is therefore an object of the invention to provide an air control system that provides a greater degree of control to the occupant beyond that provided by the unit control system.

Therefore, according to one aspect of the present invention, there is provided an air distribution system for an air conditioning installation, the system including: a distribution assembly for distributing a supply air flow from an air conditioning unit to a plurality of zones; a zone damper for each zone for controlling the flow of air to said zone; a zone temperature control means for each zone for controlling the position of the zone damper as a function of a temperature set-point set by an occupant of the zone, the zone temperature control means being adapted to maintain the zone at the temperature set-point; a master control system including means for measuring the static pressure of the supply air-flow within the distribution assembly, and means for maintaining said static pressure at a predetermined set point pressure by overriding the zone 20 temperature control means and controlling the position of one or more of the zone dampers to allow air to be bled into one or more said zones.

The master control system may further measure the temperature of the supply air from the air conditioning unit and advise the zone temperature control means of said supply air temperature. The zone temperature control means may then incrementally open or close the zone damper to control the supply air-flow to the zone based on difference between the supply air temperature and the temperature set-point for the zone.

According to another aspect of the present invention, there is provided a multi-zone air conditioning installation including an air conditioning unit and an air distribution system as described above.

The air distribution system according to the present invention is therefore an "air side" control system which can operate independently from the unit control system of an air conditioning unit.

Whether fitted at the time of manufacture or purchased separately, a unit control system is a fundamental part of the air-conditioning unit. Based on a unit set point temperature the unit control system controls the fan speed and operation of the compressor within the air-conditioning unit to provide a volume of air that will bring the house air temperature in compliance with the temperature set point of the house. The temperature transducer that supplies data to the unit control system may be located in the collection assembly and thus in the return duct adjacent to the return air grille. The return air grille may be placed centrally within the house so as to return to the air-conditioning unit air having a temperature which is equal to the average temperature within the house.

The provision of the master control system is quite separate and distinct from the unit control system, with the master control system having "air-side control" only. The master control system may measure and react to only the supply air temperature and the static pressure within the supply duct forming the up-stream portion of the distribution assembly.

The distribution assembly itself is a collective term for the arrangement of 20 supply ducts feeding supply air-flow to each of the plurality of zones, with the zone dampers being located within the distribution assembly for varying the volume of supply air-flow to each zone.

-A zone damper may be located in line with the supply duct for the respective zone, and under the influence of the zone temperature control means, may open or close and thus vary the supply air-flow to the zone. The zone damper may be fitted with means to incrementally open or close and thus the system may be able to accommodate partial opening or partial closing. To *achieve this partial opening or closing, the damper may have fitted a biasing means such as a modulating or stepper motor providing the incremental bias to partially open or close the damper.

The zone temperature control means provide means to the occupant of the zone to establish the set point temperature for that zone, and thus may be a thermostat or other analog or digital means to establish the set point temperature.

The zone temperature control means of each zone may include a first measurement means which measures the actual temperature within that zone, so that the actual temperature may be compared with the desired temperature as represented by the temperature set point. The master control system may include a second measurement means located in the supply duct adjacent the air conditioning unit for measuring the supply air-flow temperature that is delivered by the air-conditioning unit. Further located in the supply duct adjacent the air conditioning unit, as part of the master control system, may be a pressure measurement means to measure the static pressure of the supply air-flow as distinct from the velocity head created by the supply air-flow. The pressure measurement means is capable of measuring increases and decreases in the static pressure within the supply duct, which under normal circumstances would be attributable to the build up in pressure caused by resistance to the supply airflow passing through the dampers of each of the zones.

Within each zone is located the zone temperature control means which S provides control of the zone damper for that zone, and specifically the degree to 20 which the damper opens or closes for the free flow of supply air. In determining Swhether to open or close the damper, the zone temperature control means may assess the actual temperature within the zone, the temperature set point and the supply air-flow temperature supplied by the master control system and determine whether that zone requires heating or cooling, and thus whether the damper requires opening or closing in order for the actual temperature within that zone to converge with the temperature set point.

Preferably, each zone may be turned on or off. In referring to whether a zone may be on or may be off, this relates to whether the zone temperature control means of that zone is on or off, and thus whether it has control over the damper within that zone.

Preferably, if an increase in static pressure is detected by the pressure measurement means which is caused by the dampers within those zones which are on, restricting the supply air-flow entering those zones, as the temperature within those zones approaches their set-point temperatures then in order to reduce the static pressure the master control system may bleed excess supply air-flow to the OFF zones by partially or fully opening the dampers within those OFF zones.

It should be noted that the master control system may only exercise control over the dampers when the static pressure exceeds a pre-set maximum pressure.

Preferably, the master control system may bleed excess supply air-flow to all the OFF zones simultaneously. Alternatively, the master control system may bleed air to selected OFF zones based on predetermined preferences or other conditions.

Preferably, if following opening of all the dampers within the OFF zones, the static pressure remains higher than the predetermined maximum pressure, the master control system may over-ride the zone temperature control means within the ON zones and sequentially open the respective dampers and thus bleed air into the ON zones.

If all the zones are ON zones, the master control system may sequentially open dampers of each ON zone as required.

More preferably, one or more zones may be designated as non over-riding 20 zones in that the master control system in over-riding the ON zones is unable to over-ride those designated zones.

In a further aspect of the present invention, there is provided a method for controlling an air conditioning system, the system including a distribution assembly for distributing air from an air conditioning unit to a plurality of zones, a zone damper for each zone for controlling the flow of air to said zone, the method including the steps establishing a temperature set-point within the zone, controlling the position of the damper within the zone so as to maintain the temperature set-point measuring the static pressure of the supply air flow within the distribution assembly, overriding a zone temperature control means, controlling the position of one or more of the zone dampers to allow air to be bled into one or more said zones, for maintaining said static pressure at a predetermined set-point pressure.

Preferably the method may further include the step of turning a zone ON or OFF wherein an OFF zone may be used in preference to overriding an ON zone.

For the purposes of clarification and exemplification, the following description of one possible embodiment of the invention is provided.

The addition of the air control system to an air-conditioning installation may provide means to optimise conditions within each zone. As with conventional airconditioning systems, zones can be designated as day cycle, night cycle or infrequently used cycle zones, by designating zones as on or off, depending on use at that particular time of the day. In the case of conventional systems where occupants in different on zones wish to vary the temperature from that supplied by the air-conditioning unit, it is necessary to vary the set point temperature of the air-conditioning unit itself. In so doing, occupants within two zones will need to compromise their desired environment as varying the set point of the airconditioning unit will favour one zone over another.

The present invention provides means to provide each occupant within each zone a way to vary the temperature within each zone but not at the expense of other zones. Thus, by establishing the temperature set point of the unit, the occupants can ensure that supply air-flow at a desired temperature is of sufficient capacity to satisfy the needs of all the serviced zones. Then each occupant within each zone through the zone temperature control means, is able to modify the temperature within that zone by varying the volume of supply air-flow entering that zone. In the case of the supply air-flow being fully utilised by all the on S"zones, then there will be no back pressure in the distribution assembly, and thus the static pressure will stay within the required limits and so not activate the master control system. Where the preferences of the occupants within each zone are such that there is an excess of supply air-flow to meet the needs of the on zones, this will lead to a back pressure increasing within the distribution assembly, and thus increasing the static air pressure. Once the predetermined maximum static pressure is exceeded the master control system is able to bleed the excess supply air-flow to those zones that are not currently being used, for instance the bedrooms during the day.

In those cases where the supply air-flow is of a sufficient volume such that with all the off zones fully open and still static air pressure has not dropped below the predetermined maximum, then the master control system is able to sequentially over-ride each of the on zones so that although the desired temperatures within each on zone may be compromised, the master control system is able to limit this disruption by spreading the excess supply air-flow among all of the on zones.

As an alternative, one or more of the on zones can be designated as non over-rideable such that no excess air is ever supplied to this zone, and so the temperature remains ideal throughout, this case being particularly suitable for a sick room, a computer room or other rooms where a variation in temperature is undesirable.

In the case of the master control system regularly over-riding the on zones, the occupants need only reduce the set point temperature of the unit so as to alter the volume and temperature of supply air-flow, and thus bring the house into balance with relative ease.

Description of Preferred Embodiment It will be convenient to further describe the present invention with respect to the accompanying drawings which illustrate possible arrangements of the 20 invention. Other arrangements of the invention are possible, and consequently the particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

Figure 1 is a schematic view of the air-conditioning installation according to the present invention.

Figure 2 is a flow chart of the process according to the present invention.

Figure 1 shows the air-conditioning installation 1 which includes an airconditioning unit 2, a unit control system 3 to control the air-conditioning unit compressor and fan, at least one return air grille 4, a plurality of distribution nodes at least one zone 6 associated with each distribution node 5, and at least one diffuser 7, for each zone 6. These elements are all connected through a network of return ducts 8, connecting the return air grille 4 to the air-conditioning unit 2, a further network of supply ducts 9 connecting the air-conditioning unit 2 to each 9 distribution node 5. The distribution nodes 5 are then connected to the zones 6 by a network of zone ducts Within each distribution node 5 there is included a damper 13 and damper actuator for each zone 6. Zone temperature measurement means are used to measure the actual temperature. The zone temperature measurement means is part of a zone temperature controller, possibly a form of thermostat located in each zone, which is also used by an occupant of that zone to register the preferred temperature set-point 14 for that zone. The zone temperature controller uses this temperature data in order to determine whether to open or close the respective damper 13 for that zone.

Temperature measurement means and static pressure measurement means 16 are each provided in the supply duct 9. Each of these measurement means 15 and 16 provides information to a master control system 17, said master control system 17 acting to communicate the supply air temperature as determined by temperature measurement means 15 to each of the zone temperature controllers. The zone temperature controllers, as described previously, therefore use three sets of data to determine whether the damper 13 is to be incrementally opened or closed, the three sets of data being, the actual temperature within the zone, the set point temperature as established by the zone 20 temperature controller 14, and the supply air temperature as communicated by the master control system 17. For example, if the set point temperature in the zone is set at 250 C the actual temperature within the zone is measured at 30' C, and the supply air temperature is measured at 200 C, the zone temperature controller will operate the damper 13 so as to open the damper and make use of 25 the cooler supply air-flow.

In this particular case the master control system 17 will take no action other than to communicate the supply air temperature to each of the zone temperature controller. In so doing, occupants within each individual zone are able to establish set point temperatures within each of their zones and the respective zone temperature controllers are able to determine actions which will best optimise the flow of air into the zone so as to best achieve the set point temperature for their respective zones.

The capacity of the air-conditioning unit is based on servicing the largest capacity zone or zones that may reasonably be expected to be operating at one time. Thus, for a daytime cycle it would be expected that the kitchen, lounge room, family room etc., may all require air-conditioning at one time, and the airconditioning unit will be sized accordingly. In this case, the night cycle zones, such as the bedrooms, would have their respective zone temperature controllers switched off. In operating the air-conditioning unit a unit set point temperature is established and is based on providing a sufficient volume of cool air so as to service the zones in question. Where that volume of air may be at any given time greater than is required to service the ON zones, the zone temperature controllers will each operate their respective dampers so as to limit the supply of air into those zones, so as to best maintain or achieve the zone set point temperature.

The subsequent restriction in air-flow created by the partially or fully closed dampers will lead to a back pressure being caused within the supply air duct 9.

This back pressure will be detected by the pressure measurement means 16, and subsequently will activate the master control system 17. It is the function of the master control system 17 to maintain the static air pressure within the supply air duct 9 at a particular set point pressure, or alternatively within an acceptable S° range of pressures. When that set point pressure is exceeded the master control 20 system takes control of the dampers within each of the OFF zones, and opens the dampers within the OFF zones so as to bleed the excess supply air to those zones. In so doing, the ON zones are unaffected by the excess supply air being generated by the air-conditioning unit, with the temperature of the OFF zones being immaterial as they are not occupied at that time.

In the event that the bleeding of the excess air to the OFF zones is insufficient to lower the static air pressure, then the master control system 17 will sequentially over-ride the dampers within each ON zone so as to partially bleed excess air into each of those zones. This will have the effect of marginally disrupting the occupant preferences within each of those zones, but as the overriding of the ON zones is sequential the disruption to the environment within each zone is minimised. If the over-riding of the ON zones is required for an extended period so as to bleed the excess supply air, and the disruption caused by the 11 over-riding is such that it is intolerable to the occupants within each of the ON zones, it is likely that this is as a result of having too high or too low a set point temperature for the air-conditioning unit itself. In this case, in order to meet the requirements of the set point temperature, the air-conditioning unit is supplying too great a volume of air to satisfy the system as a whole. Therefore, it is a matter of one or more of the occupants varying the set point temperature of the air-conditioning unit so as to reduce the volume of air being supplied, thus reducing the back pressure and making it unnecessary for the master control system 17 to have to over-ride the ON zones. It is preferable for the efficient operation of the air-conditioning unit to vary the set point temperature of the airconditioning unit such that it does not need to bleed excess air to the OFF zones, but this is within the control of one or more of the occupants within each of the zones, and demonstrates the flexibility of the master control system 17 in providing optimum conditions within each of the zones.

Figure 2 shows the flow diagram associated with the functioning of the master control system 17 of the air control system of the invention. Prior to the process commencing the system initializes itself by detecting the number of zones within the network 101, reading input from each transducer, place the zone temperature controllers on standby and opens all dampers.

The first step 102 of the process determines which of the zones are OFF, that is, the zone temperature controller is not functioning. Any zones which were overridden when ON, and have now been turned OFF, are "unover-ridden" so as to ensure the associated dampers are fully closed 103. The system then tests 104 to see if any ON zones have been over-ridden, and if so, then all OFF zones are fully opened 105.

Notwithstanding this rationalization of OFF zones, the system checks the status of the static air pressure 106, and tests whether it is within the acceptable operating range 107, or has been exceeded by back pressure being formed from restriction of flow in the zones. If the pressure is higher than desirable 108, a test of whether the OFF zones are fully open is conducted 109. If so, then the first zone within a predetermined sequence is tested 110 as to whether it is both overridden and fully open, and if not, then it is overridden and opened 113. The system then re-tests the pressure. If the pressure remains high, or if the first zone is already over-ridden and open, the next zone within the sequence is tested 111, 112, and so on until all the pre-determined zones are assessed and controlled 114, 115, or the pressure is brought under control. If instead, all the OFF zones are not open, then all such zones are opened 91.

If the pressure is lower than the acceptable operating range 108, then all the zones are tested as to whether they are ON, and thus outside the direct control of the master control system. If there are some zones, it is determined whether any have been overridden already 117, and if not, then all the OFF zones are closed 120.

All those zones which have been overridden are then sequentially closed 118, with the pressure being tested following each closure 119, to determine the effect and necessity to move to the next zone in the sequence.

A further feature of the master control system is where the occupant can configure the system 121 to automatically turn all the zones OFF, after a delay of fifteen seconds 123 after detecting the air conditioning unit has been switched off 117. If selected 121, the zones are turned OFF, and all the dampers are subsequently opened 125, 126.

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Claims (19)

1. An air distribution system for an air conditioning installation, the system including: a distribution assembly for distributing a supply air flow from an air conditioning unit to a plurality of zones; a zone damper for each zone for controlling the flow of air to said zone; a zone temperature control means for each zone for controlling the position of the zone damper as a function of a temperature set-point set by an occupant of the zone, the zone temperature control means being adapted to maintain the zone at the temperature set-point; a master control system including means for measuring the static pressure of the supply air-flow within the distribution assembly, and means for maintaining said static pressure at a predetermined set point pressure by overriding the zone temperature control means and controlling the position of one or more of the zone dampers to allow air to be bled into one or more said zones.

2. The air distribution system according to claim 1 wherein the master control system further includes means to measure the temperature of the supply air flow and communicating said temperature to the zone temperature control means.

S3. The air distribution system according to claim 1 or claim 2 wherein the distribution assembly includes ductwork leading from the air conditioning unit to each zone and diffusers located in each zone for distributing the supply air flow to the respective zone.

4. The air distribution system according to any one of the preceding claims wherein the means for measuring the static pressure includes at least one pressure transducer located adjacent the air conditioning unit.

The air distribution system according to any one of the preceding claims wherein the zone damper is capable of an incremental change in position. 14

6. The air distribution system according to claim 5 wherein the change in incremental position is provided by a modulating or stepper motor.

7. The air distribution system according to any one of the preceding claims wherein the zone temperature means includes a thermostat.

8. The air distribution system according to any one of the preceding claims wherein the master control system further includes a second measurement means for measuring the supply air flow temperature, said second measurement means being located adjacent the air conditioning unit.

9. The air distribution system according to any one of the preceding claims wherein each zone may be selectively turned on or off.

The air distribution system according to claim 9 wherein the one or more zones into which air is bled includes OFF zones. :o

11. The air distribution system according to any one of the preceding claims o wherein the means for maintaining static pressure is activated only when the static pressure exceeds a pre-determined maximum pressure.

12. The air distribution system according to any one of claims 9 to 11 wherein excess air is bled into all of the off zones simultaneously.

13. The air distribution system according to any one of claims 9 to 11 wherein •oooo air is bled into selected off zones based on a pre-determined preference.

14. The air distribution system according to any one of claims 9 to 13 wherein following excess air being bled to off zones, the master control system overrides the zone temperature control means in the on zones to bleed further excess air only where the static pressure exceeds the pre-determined maximum pressure after the off zone bleed.

The air distribution system according to claim 14 wherein in overriding the zone temperature control means of the on zones, the master control system will sequentially open dampers in each of the on zones until the static pressure is equal or less than the pre-determined maximum pressure.

16. The air distribution system according to claim 14 or 15 wherein zones may be designated as non-overriding zones in that the master control system is prevented from overriding the zone temperature control means of non-overriding zones.

17. A method for controlling an air conditioning system, the system including a distribution assembly for distributing air from an air conditioning unit to a plurality of zones, a zone damper for each zone for controlling the flow of air to said zone, the method including the steps establishing a temperature set-point within the zone, controlling the position of the damper within the zone so as to maintain the temperature set-point measuring the static pressure of the supply air flow within S. the distribution assembly, overriding a zone temperature control means, S"controlling the position of one or more of the zone dampers to allow air to be bled into one or more said zones, for maintaining said static pressure at a *oo* predetermined set-point pressure.

18. The method of claim 17 further including the step of turning a zone on or off wherein an off zone is used in preference to overriding an on zone.

19. A multi-zone air conditioning installation including an air conditioning unit and an air distribution system according to any one of claims 1 to 16.