Differential temperature control

• US 5,544,697 A
• Filed: 11/27/1987
• Issued: 08/13/1996
• Est. Priority Date: 09/02/1983
• Status: Expired due to Fees

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Clark, William E.
• Primary Examiner(s): Ford, John K.
• Application Number:
  US07/125,919
• Time in Patent Office: 3,182 Days
• Field of Search: 236/49, 236/1 B, 236/1 C, 165/22, 165/12, 165/2
• US Class Current: 165/209
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/65 for selecting an operating mode
• CPC Class Codes: F24F 11/76 by means responsive to temperature, e.g. bimetal springs
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 2013/087 using inflatable bellows
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/40 Pressure, e.g. wind pressure
• CPC Class Codes: G05D 23/1917 using digital means
• CPC Class Codes: G05D 23/1925 using a combination of auxiliary electric and non-electric power
• CPC Class Codes: G05D 23/1934 each space being provided with one sensor acting on one or more control means
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

The difference between the zone temperature and the scheduled setpoint, or Δt, is the basic data from each zone. Communication between the air handler control and the air terminal control is provided via the air system control so that the system is temperature, rather than pressure, responsive.

Claims

1. A method for controlling an air distribution system including a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with a corresponding heating and cooling set point for the zone, and responsive thereto determining whether each zone requires heating or cooling;

determining whether the majority of the zones require heating or cooling and responsive thereto placing all of the terminals in a heating or cooling mode of operation;

supplying heated or cooled air in accordance with the mode of operation of the terminals;

comparing the temperature in each zone with the set point corresponding to the mode of operation to determine terminal satisfaction in each zone which is defined by the zone being at the set point corresponding to the mode of operation or within a predetermined dead band centered on the set point corresponding to the mode of operation;

operating each of the terminals so as to achieve terminal satisfaction; and

controlling the air handler to supply air to enable the terminals to achieve terminal satisfaction.

2. The method of claim 1 wherein the step of controlling the air handler further includes the step of:

maintaining the number of terminals unable to achieve terminal satisfaction within a predetermined range.

3. The method of claim 1 further including the steps of:

determining whether each terminal is operating in the dead band range corresponding to the mode of operation; and

overriding the operation of each terminal which is out of the dead band range corresponding to the mode of operation by appropriately repositioning the terminal damper if it is still within its range of movement.

4. The method of claim 1 further including the step of:

periodically sampling all of the terminals unable to achieve terminal satisfaction and causing the system to operate in the mode having the most terminals unable to achieve terminal satisfaction.

5. A method for controlling an air distribution system including a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with a corresponding heating and cooling set point for the zone, and responsive thereto determining whether each zone requires heating or cooling;

determining whether the majority of the zones require heating or cooling and responsive thereto placing all of the terminals in a heating or cooling mode of operation;

supplying heated or cooled air in accordance with the mode of operation of the terminals;

comparing the temperature in each zone with the set point corresponding to the mode of operation to determine terminal satisfaction in each zone which is defined by the zone being at the set point corresponding to the mode of operation or within a predetermined dead band centered on the set point corresponding to the mode of operation;

operating each of the terminals so as to achieve terminal satisfaction;

controlling the air handler to supply air to enable the terminals to achieve terminal satisfaction so as to maintain the number of terminals unable to achieve terminal satisfaction within a predetermined range; and

resetting the temperature of the supply air within a predetermined range when the step of determining terminal satisfaction in each zone determines that there is a predetermined degree of undercooling or overcooling for all of the zones.

6. A method for controlling an air distribution system including a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with a corresponding heating and cooling set point for the zone, and responsive thereto determining whether each zone requires heating or cooling;

determining whether the majority of the zones require heating or cooling and responsive thereto placing all of the terminals in a heating or cooling mode of operation;

supplying heated or cooled air in accordance with the mode of operation of the terminals;

comparing the temperature in each zone with the set point corresponding to the mode of operation to determine terminal satisfaction in each zone which is defined by the zone being at the set point corresponding to the mode of operation or within a predetermined dead band centered on the set point corresponding to the mode of operation;

operating each of the terminals so as to achieve terminal satisfaction;

controlling the air handler to supply air to enable the terminals to achieve terminal satisfaction so as to maintain the number of terminals unable to achieve terminal satisfaction within a predetermined range; and

resetting the temperature of the supply air within a predetermined range when the step of determining terminal satisfaction in each zone determines that there is a predetermined degree of overheating or underheating for all of the zones.

7. A method for controlling an air distribution system including a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with a corresponding heating and cooling set point for the zone, and responsive thereto determining whether each zone requires heating or cooling;

determining whether the majority of the zones require heating or cooling and responsive thereto placing all of the terminals in a heating or cooling mode of operation;

supplying heated or cooled air in accordance with the mode of operation of the terminals;

comparing the temperature in each zone with the set point corresponding to the mode of operation to determine terminal satisfaction in each zone which is defined by the zone being at the set point corresponding to the mode of operation or within a predetermined dead band centered on the set point corresponding to the mode of operation;

operating each of the terminals so as to achieve terminal satisfaction;

controlling the air handler to supply air to enable the terminals to achieve terminal satisfaction so as to maintain the number of terminals unable to achieve terminal satisfaction within a predetermined range; and

determining whether there is a predetermined degree of overcooling;

if there is a predetermined degree of overcooling, reducing the fan speed to the minimum acceptable amount;

if there is a predetermined degree of overcooling and fan speed is at the minimum acceptable amount, incrementally raising the supply air temperature within a predetermined range until the limits of the range are met or until the degree of overcooling has been reduced to a predetermined level.

8. A method for controlling an air distribution system including a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with a corresponding heating and cooling set point for the zone, and responsive thereto determining whether each zone requires heating or cooling;

determining whether the majority of the zones require heating or cooling and responsive thereto placing all of the terminals in a heating or cooling mode of operation;

supplying heated or cooled air in accordance with the mode of operation of the terminals;

comparing the temperature in each zone with the set point corresponding to the mode of operation to determine terminal satisfaction in each zone which is defined by the zone being at the set point corresponding to the mode of operation or within a predetermined dead band centered on the set point corresponding to the mode of operation;

operating each of the terminals so as to achieve terminal satisfaction;

controlling the air handler to supply air to enable the terminals to achieve terminal satisfaction;

resetting the temperature of the supply air within a predetermined range when the step of determining terminal satisfaction in each zone determines that there is a predetermined degree of undercooling or overcooling for all of the zones.

9. A method for controlling an air distribution system including a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with a corresponding heating and cooling set point for the zone, and responsive thereto determining whether each zone requires heating or cooling;

determining whether the majority of the zones require heating or cooling and responsive thereto placing all of the terminals in a heating or cooling mode of operation;

supplying heated or cooled air in accordance with the mode of operation of the terminals;

comparing the temperature in each zone with the set point corresponding to the mode of operation to determine terminal satisfaction in each zone which is defined by the zone being at the set point corresponding to the mode of operation or within a predetermined dead band centered on the set point corresponding to the mode of operation;

operating each of the terminals so as to achieve terminal satisfaction;

controlling the air handler to supply air to enable the terminals to achieve terminal satisfaction;

periodically sampling all of the terminals unable to achieve terminal satisfaction such that the degree to which the terminals are unable to achieve terminal satisfaction is taken into account in determining which mode has the most terminals unable to achieve terminal satisfaction; and

causing the system to operate in the mode having the most terminals unable to achieve terminal satisfaction.

10. A method for controlling the pull down balance of an air distribution system on start up where the air distribution system includes a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with the corresponding heating and cooling set points, and responsive thereto determining whether each zone requires heating or cooling;

determining whether the majority of the zones require heating or cooling and responsive thereto placing all of the terminals in the same mode of operation;

if cooling is required, start cooling;

comparing the temperature in each zone with the set point corresponding to the mode of operation to determine terminal satisfaction in each zone which is defined by the zone being at the set point corresponding to the mode of operation or within a predetermined dead band centered on the set point corresponding to the mode of operation;

running the air handler to supply air at the maximum desired output;

polling all terminals out Of the dead band range centered on the set point of the mode of operation thereby indicating dissatisfied terminals for the mode of operation;

averaging the dissatisfaction of the terminals;

polling the rate of change of temperature in the zones of all dissatisfied terminals which defines the pull down rate;

averaging the pull down rates for all the dissatisfied terminals;

comparing the average dissatisfaction of the terminals with a dead band of dissatisfaction;

if any terminals exceed a dead band of the average pull down rate, causing them to move toward closing; and

continuing the operation until a predetermined number of terminals in the system are satisfied.

11. A method for controlling an air distribution system including a plurality of zones which are supplied with heated or cooled air by an air handler which supplies air to the zones through air terminals comprising the steps of:

determining the temperature in each zone;

comparing the temperature in each zone with a corresponding heating and cooling set point for the zone, and responsive thereto determining whether each zone requires heating or cooling and placing all of the terminals in the same mode of operation;

determining how many zones are out of a dead band range centered on the set point of the mode of operation thereby indicating terminal dissatisfaction for the mode of operation; and

controlling the air handler responsive to the differences between the sensed temperature in each zone and the set point for the mode of operation for the corresponding zone so as to maintain the number of dissatisfied terminals within a predetermined range.

12. The method of claim 11 further including the step of:

limiting the rate of change in the amount of air supplied by the terminals to the zones and by the air handler to the terminals so as to prevent noticeable sound changes.

13. An air distribution system for controlling the supply of conditioned air to a plurality of zones comprising:

air distribution means;

air handler means for supplying conditioned air to said air distribution means;

a plurality of air terminal means operatively connected to said air distribution means for controlling the flow of conditioned air into a plurality of zones;

said air terminal means in each zone including;

means for sensing the temperature in each zone;

means for setting the set points for each zone; and

means for controlling each of said terminals responsive to the difference between the sensed temperature in each zone and the set

point for the corresponding zone;

means for controlling said air handler means responsive to said differences between the sensed temperature in each zone and the set point for the corresponding zone;

means for determining how many zones are calling for heating and how many are calling for cooling; and

means for placing all of said terminal means in either a direct acting or reverse acting mode in accordance with whether most of the zones are calling for cooling or heating, respectively.

14. An air distribution system for controlling the supply of conditioned air to a plurality of zones comprising:

air distribution means;

air handler means for supplying conditioned air to said air distribution means;

a plurality of air terminal means operatively connected to said air distribution means for controlling the flow of conditioned air into a plurality of zones;

said air terminal means in each zone including;

means for sensing the temperature in each zone;

means for setting the set points for each zone; and

means for controlling each of said terminals responsive to the difference between the sensed temperature in each zone and the set point for the corresponding zone;

means for controlling said air handler means responsive to said differences between the sensed temperature in each zone and the set point for the corresponding zone;

means for determining how many of said terminals are dissatisfied which is defined as being outside of a dead band centered on the set point for the mode of operation when all of said terminals are acting in the same mode; and

means for causing said means for controlling said air handler means to operate to maintain the number of dissatisfied terminals within a predetermined range.

15. An air distribution system for controlling the supply of conditioned air to a plurality of zones comprising:

air distribution means;

air handler means for supplying conditioned air to said air distribution means;

a plurality of air terminal means operatively connected to said air distribution means for controlling the flow of conditioned air into a plurality of zones;

said air terminal means in each zone including;

means for sensing the temperature in each zone;

means for setting the set points for each zone; and

means for controlling each of said terminals responsive to

dissatisfaction which is defined by the difference between the sensed temperature in

each zone and the set point for the corresponding zone;

means for controlling said air handler means responsive to said differences between the sensed temperature in each zone and the set point for the corresponding zone.

16. The air distribution system of claim 15 further comprising means for resetting the temperature of the supply air.