AIR CONDITIONING SYSTEM HAVING ACTIVELY CONTROLLED AND STABILIZED HOT GAS REHEAT CIRCUIT

• US 20160273815A1
• Filed: 03/19/2015
• Published: 09/22/2016
• Est. Priority Date: 03/19/2015
• Status: Active Grant

• Current Assignee: Nortek Global HVAC, LLC (Melrose Industries Plc)
• Original Assignee: Nortek Global HVAC, LLC (Melrose Industries Plc)
• Inventors: Downie, James Patrick, Reed, Richard Brian, Blasko, Richard Gerard, McKissack, John Patrick, Gholap, Avinash Keshavrao
• Granted Patent: US 10,066,860 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F24F 3/153 with subsequent heating, i.e. with the air, given the required humidity in the central station, passing a heating element to achieve the required temperature
• CPC Class Codes: F25B 2400/0403 for the condenser
• CPC Class Codes: F25B 2600/111 of condenser fans
• CPC Class Codes: F25B 2600/112 of evaporator fans
• CPC Class Codes: F25B 2600/2501 Bypass valves
• CPC Class Codes: F25B 2600/2515 Flow valves
• CPC Class Codes: F25B 2700/02 Humidity
• CPC Class Codes: F25B 2700/21161 of the fluid heated by the condenser
• CPC Class Codes: F25B 2700/21173 at the outlet
• CPC Class Codes: F25B 2700/21174 of the refrigerant at the inlet of the evaporator
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• CPC Class Codes: F25B 6/02 arranged in parallel
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A method for controlling an air conditioning system comprises routing refrigerant through an evaporator to cool air in a space, proportioning refrigerant flow from the evaporator between a condenser circuit and a hot gas reheat circuit that heats air leaving the evaporator, routing refrigerant flow from the condenser circuit and the hot gas reheat circuit through an expansion device and back to the evaporator, monitoring a first temperature at the evaporator, stabilizing proportioning of refrigerant flow between the condenser circuit and the hot gas reheat circuit based on the monitored first temperature.

Claims

1. A method for controlling an air conditioning system, the method comprising:

routing refrigerant through an evaporator to cool air in a space;

proportioning refrigerant flow from the evaporator between a condenser circuit and a hot gas reheat circuit that heats air leaving the evaporator;

routing refrigerant flow from the condenser circuit and the hot gas reheat circuit through an expansion device and back to the evaporator;

monitoring a first temperature at the evaporator; and

stabilizing proportioning of refrigerant flow between the condenser circuit and the hot gas reheat circuit based on the monitored first temperature.

2. The method of claim 1, further comprising:

monitoring a second temperature at the hot gas reheat circuit; and

modulating fluid flow through the hot gas reheat circuit based on the monitored second temperature.

3. The method of claim 2, wherein the second temperature comprises a discharge air temperature of a reheat coil in the hot gas reheat circuit.

4. The method of claim 2, wherein the proportioned refrigerant flow is permitted to enter the hot gas reheat circuit from zero to one hundred percent of a total refrigerant flow in the air conditioning system.

5. The method of claim 2, further comprising:

monitoring a third temperature at the condenser circuit; and

controlling output of a compressor based on the monitored third temperature, the compressor flowing refrigerant through the air conditioning system.

6. The method of claim 5, wherein the third temperature comprises a leaving air temperature of the evaporator.

7. The method of claim 2, wherein the stabilization of the refrigerant flow allows proportioning of the refrigerant flow according to:

a first operation mode when the first temperature is above a preset maximum temperature;

a second operation mode when the second temperature is at or below a preset minimum temperature; and

a third operation mode when the first temperature is at or between the preset maximum temperature and the minimum temperature.

8. The method of claim 1, wherein proportioning of the refrigerant flow between the condenser circuit and the hot gas reheat circuit is controlled by a reheat algorithm that actively controls a percentage of refrigerant flow from the evaporator that flows to the condenser circuit and to the hot gas reheat circuit in order to cool and dehumidify the air of the space.

9. The method of claim 8, wherein stabilization of the proportioning of refrigerant flow between the condenser circuit and the hot gas reheat circuit is controlled by a stabilization algorithm that overrides the reheat algorithm to limit refrigerant flow through the hot gas reheat circuit based on the monitored first temperature.

10. The method of claim 9, wherein the stabilization algorithm prevents refrigerant flow through the hot gas reheat circuit when the monitored first temperature is at or below a minimum temperature.

11. The method of claim 10, wherein the stabilization algorithm allows unrestricted refrigerant flow through the hot gas reheat circuit when the monitored first temperature is above a maximum temperature.

12. The method of claim 11, wherein the stabilization algorithm linearly changes the permitted refrigerant flow through the hot gas reheat circuit when the monitored first temperature is at or between the minimum and maximum temperatures.

13. An air conditioning system comprising:

a vapor-compression circuit comprising an evaporator, a compressor, a condenser and an expansion device;

a reheat coil arranged in parallel with the condenser to form a hot gas reheat circuit;

a valve arrangement configured to proportion refrigerant flow from the compressor to the reheat coil and the condenser;

a first temperature sensor configured to sense a first temperature at the evaporator; and

a controller configured to limit proportioning of the refrigerant flow by the valve arrangement based on the first temperature.

14. The air conditioning system of claim 13, wherein the first temperature sensor is positioned at an inlet of the evaporator.

15. The air conditioning system of claim 13, wherein the controller operates the valve arrangement using a stabilization algorithm that restricts refrigerant flow through the reheat coil based on the sensed first temperature in order to prevent freezing at the evaporator.

16. The air conditioning system of claim 15, further comprising:

a second temperature sensor configured to sense a second temperature at the hot gas reheat circuit;

wherein the controller is configured to use a reheat algorithm to operate the valve arrangement based on the sensed second temperature; and

wherein the reheat algorithm is governed by the stabilization algorithm.

17. The air conditioning system of claim 16, further comprising:

a third temperature sensor configured to sense a third temperature at the vapor-compression circuit; and

a compressor configured to move refrigerant through the vapor-compression circuit;

wherein the controller is configured to control the compressor to adjust the second temperature.

18. The air conditioning system of claim 13, wherein the valve arrangement comprises:

a first valve positioned to control refrigerant flow to the condenser; and

a second valve positioned to control refrigerant flow to the reheat coil.

19. The air conditioning system of claim 18, wherein the first and second valves comprise adjustable valves configured to be operated between zero and one hundred percent capacity and at a plurality of increments therebetween.

20. A controller for an air conditioning system having a vapor-compression circuit and a hot gas reheat circuit, the controller comprising:

a first input for receiving a first temperature signal from a first temperature sensor at the hot gas reheat circuit of the air conditioning system;

a second input for receiving a second temperature signal from a second temperature sensor at an inlet of an evaporator in the vapor-compression circuit; and

circuitry configured to;

generate a valve control signal for controlling a reheat valve that controls refrigerant flow through the hot gas reheat circuit based on the first temperature signal in order to maintain a temperature of a space cooled by the evaporator; and

generate a stabilization signal to override the valve control signal based on the second temperature signal.

21. The controller of claim 20, wherein the stabilization signal comprises a close signal that fully closes the reheat valve if the second temperature signal is at or below a preset minimum temperature.

22. The controller of claim 21, wherein the stabilization signal comprises an open signal for allowing the reheat valve to fully open if the second temperature signal is above a preset maximum temperature.

23. The controller of claim 22, wherein the stabilization signal comprises a proportioning signal for gradually closing the hot gas reheat circuit valve between the preset minimum temperature and the preset maximum temperature according to a preset schedule.

24. The controller of claim 23, further comprising memory in communication with the circuitry, the memory having stored therein the preset maximum and minimum temperatures and the preset schedule.

25. The controller of claim 20, further comprising:

a third input for receiving a third temperature signal from a third temperature sensor at the vapor-compression circuit; and

wherein the circuitry is configured to generate a compressor signal to control a compressor in the vapor-compression circuit.

26. The controller of claim 20, wherein the circuitry is in electronic communication with the first and second temperature sensors and a reheat valve that receives the valve signal.