METHODS OF CONTROLLING FAN CAPACITY AND COIL CAPACITY IN HVAC SYSTEMS

• US 20140131009A1
• Filed: 11/11/2013
• Published: 05/15/2014
• Est. Priority Date: 11/09/2012
• Status: Active Grant

• Current Assignee: Trane International Inc. (Trane Technologies plc)
• Original Assignee: Trane International Inc. (Trane Technologies plc)
• Inventors: ZHOU, John, CLANIN, Thomas J.
• Granted Patent: US 9,651,321 B2
• Time in Patent Office: Days
• US Class Current: 165/104.14
• 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 11/76 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 11/81 by controlling the air supply to heat-exchangers or bypass channels
• CPC Class Codes: F24F 11/83 by controlling the supply of heat-exchange fluids to heat-exchangers
• CPC Class Codes: F24F 11/84 using valves
• CPC Class Codes: F24F 11/85 using variable-flow pumps
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F28F 27/00 Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus control arrangements in general G05
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

Methods to regulate a discharge fan and a coil of a HVAC system are described. The method may include regulating a discharge air temperature of the cooling/heating coil of the HVAC system while maintain the discharge fan at a low capacity setting. The method may also include maintaining the coil at a low discharge air temperature (or a high discharge air temperature) setting, while varying a fan capacity of the discharge fan. The method may include a discharge capacity boost that includes decreasing (or elevating) the discharge air temperature limit of the coil beyond the low discharge air temperature (or the high discharge air temperature) limit. The methods as described herein may be applicable to a HVAC system that has variable airflow capability.

Claims

1. A method of controlling a HVAC system, comprising:

maintaining a discharge fan capacity at a low fan capacity setting and varying a coil discharge air temperature between a low discharge air temperature limit and a high discharge air temperature limit;

when the coil discharge air temperature reaches the low discharge air temperature limit, varying the discharge fan capacity between the low fan capacity setting and a high fan capacity setting so as to maintain a space temperature setpoint while maintaining the low discharge air temperature limit; and

when the coil discharge air temperature reaches the low discharge air temperature limit and the discharge fan capacity reaches the high fan capacity setting, varying the coil discharge air temperature between the low discharge air temperature limit and a first boost low discharge air temperature limit that is lower than the low discharge air temperature limit.

2. The method of controlling a HVAC system of claim 1, further comprising:

when the coil discharge air temperature reaches the high discharge air temperature limit, varying the discharge fan capacity between the low fan capacity setting and the high fan capacity setting so as to maintain the space temperature setpoint while maintaining the high discharge air temperature limit.

3. The method of claim 1, further comprising:

when the coil discharge air temperature reaches the high discharge air temperature limit and the discharge fan capacity reaches the high fan capacity setting, varying the coil discharge air temperature between the high discharge air temperature limit and a boost high discharge air temperature limit that is higher than the high discharge air temperature limit.

4. The method of claim 1, wherein varying the discharge fan capacity between the low fan capacity setting and the high fan capacity setting includes, when a two-speed discharge fan with a low speed setting and a high speed setting is used in the HVAC system, varying a percentage of time to operate the two-speed discharge fan at the high fan speed setting.

5. The method of claim 1, wherein varying the discharge fan capacity between the low fan capacity setting and the high fan capacity setting includes, when a variable speed discharge fan with a variable speed between a low speed setting and a high speed setting is used, varying a discharge fan speed between the low speed setting and the high speed setting.

6. The method of claim 1, wherein varying the discharge fan capacity between the low fan capacity setting and the high fan capacity setting includes, when a three-speed discharge fan with a high speed setting, an intermediate speed setting and a low speed setting is used,

when the discharge fan capacity required to maintain the space temperature setpoint is lower than an intermediate fan capacity setting, varying a fan speed between the low speed setting and the intermediate speed setting, and

when the discharge fan capacity required to maintain the space temperature setpoint is higher than the intermediate fan capacity setting, varying the fan speed between the intermediate speed setting and the high speed setting.

7. The method of claim 1, wherein varying the airflow capacity between the minimum airflow setpoint and the maximum airflow setpoint includes varying a percentage of opening of an airflow damper.

8. The method of claim 1, further comprising:

when a variable speed compressor and a variable speed discharge fan are used in the HVAC system, calculating the low fan capacity limit based on an operation speed of the variable speed compressor.

9. A method of controlling a HVAC system with a variable speed discharge fan, comprising:

maintaining a discharge fan capacity at a low fan capacity setting and varying a coil discharge air temperature between a low discharge air temperature limit and a high discharge air temperature limit; and

when the coil discharge air temperature reaches the low discharge air temperature limit, varying a fan speed of the variable speed discharge fan between a low fan speed setting and a high fan speed setting so as to maintain a space temperature setpoint.

10. The method of claim 9, further comprising:

when the coil discharge air temperature reaches the high discharge air temperature limit, varying the fan speed of the variable speed discharge fan between a low fan speed setting and a high fan speed setting so as to maintain a space temperature setpoint while maintaining the coil discharge air temperature at the high discharge air temperature limit.

11. A method of controlling a HVAC system with a variable speed discharge fan, comprising:

maintaining a discharge fan capacity at a low fan capacity setting and varying a coil discharge air temperature between a low discharge air temperature limit and a high discharge air temperature limit; and

when the coil discharge air temperature reaches the high discharge air temperature limit, varying a fan speed of the variable speed discharge fan between a low fan speed setting and a high fan speed setting so as to maintain a space temperature setpoint.

12. The method of claim 11, further comprising:

when the coil discharge air temperature reaches the low discharge air temperature limit, varying the fan speed of the variable speed discharge fan between a low fan speed setting and a high fan speed setting so as to maintain a space temperature setpoint while maintaining the coil discharge air temperature at the low discharge air temperature limit.

13. A method of controlling a HVAC system with a three-speed discharge fan with a low speed setting, an intermediate speed setting and a high speed setting, comprising:

maintaining a discharge fan capacity at a low fan capacity setting and varying a coil discharge air temperature between a low discharge air temperature limit and a high discharge air temperature limit; and

when the coil discharge air temperature reaches the low discharge air temperature limit and when the discharge fan capacity required to maintain the space temperature setpoint is higher than the low fan capacity setting, varying a fan speed between the low speed setting and the intermediate speed setting while maintaining the discharge coil temperature at the low discharge air temperature limit,

when the coil discharge air temperature reaches the low discharge air temperature limit and when the discharge fan capacity required to maintain the space temperature setpoint is higher than the intermediate fan capacity setting, varying the fan speed between the intermediate speed setting and the high speed setting while maintaining the coil discharge air temperature at the low discharge air temperature limit.

14. The method of claim 13, further comprising:

when the coil discharge air temperature reaches the high discharge air temperature limit and when the discharge fan capacity required to maintain the space temperature setpoint is higher than the low fan capacity setting, varying a fan speed between the low speed setting and the intermediate speed setting while maintaining the discharge coil temperature at the high discharge air temperature limit; and

when the coil discharge air temperature reaches the high discharge air temperature limit and when the discharge fan capacity required to maintain space temperature setpoint is higher than the intermediate fan capacity setting, varying the fan speed between the intermediate speed setting and the high speed setting while maintaining the discharge coil temperature at the high discharge air temperature limit.

15. A HVAC system, comprising:

a fan configured to provide a variable fan capacity between a high fan capacity setting and a low fan capacity setting;

a coil configured to provide a variable discharge air temperature between a high discharge air temperature limit and a low discharge air temperature limit; and

a controller configured to control the variable fan capacity of the fan and the variable discharge air temperature of the coil so as to maintain a space temperature setpoint;

wherein when the variable discharge air temperature reaches the high discharge air temperature limit, the controller is configured to vary the variable fan capacity of the fan to maintain the space temperature setpoint while maintaining the variable discharge air temperature of the coil at the high discharge air temperature limit;

when the variable discharge air temperature reaches the low discharge air temperature limit, the controller is configured to vary the variable capacity of the fan to maintain the space temperature setpoint while maintaining the variable discharge air temperature of the coil at the low discharge air temperature limit; and

when the variable discharge air temperature is between the high discharge air temperature limit and the low discharge air temperature limit, the controller is configured to vary the variable discharge air temperature between the high discharge air temperature limit and the low discharge air temperature limit to maintain the space temperature setpoint while maintaining the variable capacity of the fan at the low fan capacity setting.

16. The HVAC system of claim 15,

wherein when the coil discharge air temperature reaches the low discharge air temperature limit and the discharge fan capacity reaches the high fan capacity setting, varying the coil discharge air temperature toward a first boost discharge air temperature that is lower than the low discharge air temperature limit;

or

when the coil discharge air temperature reaches the high discharge air temperature limit and the discharge fan capacity reaches the high fan capacity setting, varying the coil discharge air temperature toward a second boost discharge air temperature that is higher than the high discharge air temperature limit.