Heater interlock control for air conditioning system

• US 20080237217A1
• Filed: 03/27/2007
• Published: 10/02/2008
• Est. Priority Date: 03/27/2007
• Status: Active Grant

• Current Assignee: Trane International Inc. (Trane Technologies plc)
• Original Assignee: American Standard International Inc (Trane Technologies plc)
• Inventors: Helt, Robert W.
• Granted Patent: US 8,746,584 B2
• Time in Patent Office: Days
• US Class Current: 219/485
• CPC Class Codes: F24D 19/1009 for central heating
• CPC Class Codes: F24D 19/1087 system using a heat pump
• CPC Class Codes: F24H 3/002 using electric energy supply

Abstract

An air conditioning apparatus, including an electric motor driven blower for circulating air through a cabinet, also includes one or more electric heating elements and a system controller operable to control energization of the heating elements and the blower motor at predetermined operating conditions by way of suitable relay or control elements. The system includes a heating interlock relay to prevent energization of the one or more heating elements if the blower motor is inoperable, operating at other than a predetermined range of speeds or the system controller detects a malfunctioning heating element control relay or the like.

Claims

1. In an air conditioning apparatus including a cabinet, an air blower including an electric blower motor for propelling air from an air inlet in said cabinet to an air outlet, at least one electric heating element disposed in an air flowstream propelled by said blower through said cabinet, a thermostat for sensing the temperature of an enclosed space being supplied with conditioned air by said apparatus, and a control system including a system controller operably connected to said thermostat for receiving control signals, said system controller being operable to communicate control signals to said blower motor and said at least one heating element, and a heater interlock operable to prevent energization of said heating element dependent on an operating condition of said blower motor.

2. The invention set forth in claim 1, wherein:

said control system includes a heater relay operable to be controlled by said system controller to supply electrical power to said at least one heating element, said heater interlock being interposed said at least one heating element and said heater relay.

3. The invention set forth in claim 2, including:

a human operable interface connected to said system controller and including a visual display, said visual display being operable to display a fault signal if at least one of said heater interlock and said heater relay are not in a condition as commanded by said system controller.

4. The invention set forth in claim 2, wherein:

said interface is operable to effect setting said system controller to select a default blower speed for a fault condition wherein any one of said heater relay and said heater interlock has malfunctioned.

5. The invention set forth in claim 2, wherein:

said blower motor includes a motor controller for receiving command signals to operate said blower motor in a predetermined direction and at a predetermined speed, said motor controller being in communication with said system controller for communicating the status of said blower motor to said system controller.

6. The invention set forth in claim 2, wherein:

at least one of said heater relay and said heater interlock includes means operably connected to said system controller for communicating a status signal to said system controller.

7. The invention set forth in claim 1, wherein:

said blower motor is a permanent split capacitor (PSC) motor.

8. The invention set forth in claim 1, wherein:

said blower motor is a variable speed motor.

9. The invention set forth in claim 1, wherein:

said blower motor is a constant torque motor.

10. The invention set forth in claim 1, wherein:

said blower motor is a variable speed motor and said system controller is operable to cause said heater interlock to prevent energization of said at least one heating element if the speed of said blower motor is less than a predetermined amount.

11. The invention set forth in claim 1, wherein:

said system controller is operable to cause said heater interlock to prevent energization of said at least one heating element if the speed of said blower motor is greater than a predetermined maximum.

12. The invention set forth in claim 1, wherein:

said system controller is operable to cause said blower motor to operate at a predetermined maximum speed if a signal is being furnished by said system controller to energize said at least one heating element.

13. A method for operating an air conditioning apparatus, said apparatus including a cabinet, an air blower including an electric blower motor for propelling air from an air inlet to an air outlet of said cabinet, and at least one electric heating element disposed in an air flowstream propelled by said blower through said cabinet, said apparatus further comprising a first temperature sensor for sensing the temperature of an enclosed space being supplied with conditioned air by said apparatus and a control system including a system controller operably connected to said first sensor, and to a second temperature sensor for sensing the temperature of air being discharged from said apparatus, said control system further including a heater interlock operable to prevent energization of said heating element, said method including the steps of:

monitoring at least one of an operating condition of said blower motor and a limit temperature of air being circulated by said blower; and

causing said heater interlock to prevent energization of said heating element dependent on one of said operating condition and said limit temperature.

14. The method set forth in claim 13 including the step of:

causing said heater interlock to prevent energization of said heating element if the speed of said blower motor is less than a predetermined amount.

15. The method set forth in claim 13 including the step of:

causing said heater interlock to prevent energization of said heating element if said blower motor is not rotating.

16. The method set forth in claim 13 including the step of:

providing a heating element relay, monitoring the operating condition of said relay and causing said heater interlock to prevent energization of said heating element if the status of said relay is not one commanded by said system controller.

17. The method set forth in claim 13 including the step of:

causing said heater interlock to prevent energization of said heating element if said blower motor is not rotating in a direction commanded by said system controller.

18. The method set forth in claim 13 including the step of:

causing said heater interlock to prevent energization of said heating element if said blower motor is not producing a torque commanded by said system controller.

19. The method set forth in claim 13 including the step of:

causing said heater interlock to prevent energization of said at least one heating element if one of the rate of change of temperature sensed by said second temperature sensor and the temperature sensed by said second temperature sensor is greater than a predetermined amount.

20. The method set forth in claim 13 including the step of:

causing said heater interlock to prevent energization of said heating element if a motor control relay is not in a condition commanded by said system controller.