Diagnostics for a heating and cooling system

• US 5,689,963 A
• Filed: 09/12/1996
• Issued: 11/25/1997
• Est. Priority Date: 05/03/1995
• Status: Expired due to Term

• Current Assignee: Emerson Climate Technologies Incorporated (Emerson Electric Company)
• Original Assignee: Copeland Corporation LLC (Emerson Electric Company)
• Inventors: Bahel, Vijay, Pham, Hung, Hickey, Mickey, Millet, Hank, Greschl, Gerald L., Herroon, Gregory P.
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US08/712,904
• Time in Patent Office: 439 Days
• Field of Search: 62/129, 62/126, 62/127, 62/228.3, 62/180, 62/179, 62/160, 62/208, 62/209, 62/203, 62/204
• US Class Current: 62/129
• CPC Class Codes: F25B 13/00 Compression machines, plants or systems, with reversible cycle defrosting cycles F25B47/02
• CPC Class Codes: F25B 2313/0293 related to the indoor fan, e.g. controlling speed
• CPC Class Codes: F25B 2313/0294 related to the outdoor fan, e.g. controlling speed
• CPC Class Codes: F25B 2313/0315 Temperature sensors near the outdoor heat exchanger
• CPC Class Codes: F25B 2600/2513 Expansion valves
• CPC Class Codes: F25B 2700/02 Humidity
• CPC Class Codes: F25B 2700/2104 of an indoor room or compartment
• CPC Class Codes: F25B 2700/2106 of fresh outdoor air
• CPC Class Codes: F25B 2700/21152 at the discharge side of the compressor
• CPC Class Codes: F25B 49/005 of safety devices F25B49/02 and F25B49/04 take precedence

Abstract

Compressor discharge temperature, ambient outdoor air temperature and thermal load are used as control parameters for controlling the expansion valve setting and indoor fan speed. Diagnostics monitor a feedback signal from the fan motor to detect fan over-speed and increased speed due to decreased air flow caused by a dirty indoor air filter. Discharge pressure of the compressor is monitored to detect a blocked outdoor fan. The difference between actual and optimum compressor discharge temperatures and suction pressure of the compressor are monitored to detect a stuck-closed expansion valve or low refrigerant charge. Compressor "short-cycling" is limited to prevent reduced reliability of the compressor. The difference between compressor discharge temperature and outdoor coil temperature is measured before and after startup to detect compressor failure.

Claims

1. A controller for a heat pump system which operates in heating and cooling modes and is of the type having a compressor for discharging refrigerant through an expansion valve (EXV) into a heat exchanger, comprising:

a first sensor for sensing a first parameter indicative of the actual temperature of the refrigerant discharged from said compressor; and

at least one control processor having means for effecting a diagnostic procedure that;

(a) determines an optimum discharge temperature;

(b) generates a differential temperature by taking the difference between the actual discharge temperature and the optimum discharge temperature; and

(c) executes a low pressure diagnostic procedure if said differential temperature is less than a first parameter.

2. The controller for a heat pump system of claim 1 further comprising:

a second sensor for sensing a second parameter indicative of the ambient air temperature;

a third sensor for sensing a third parameter indicative of thermal load on the heat pump system, wherein said at least one control processor calculates said optimum discharge temperature based on said second and third parameters.

3. The control system of claim 2 wherein said third sensor comprises:

a room temperature sensor for sensing a quantity indicative of room temperature;

a means for establishing a desired temperature set point;

a demand counter for accumulating a value indicative of thermal load; and

a load determining system for comparing said room temperature with said desired temperature set point and for altering the value accumulated by said demand counter based on said comparison.

4. The controller for a heat pump system of claim 1 further comprising:

a low pressure cutout (LPCO) means coupled to said compressor for disconnecting said compressor when pressure on an inlet side of said compressor falls below a fourth parameter and for reconnecting said compressor when said pressure rises above a fifth parameter,

wherein when said LPCO means disconnects said compressor, said at least one control processor, coupled to said low pressure cutout means and said EXV, executes said low pressure malfunction diagnostic that;

(a) attempts to free said EXV,

(b) operates said heat pump at default settings, and

(c) increments a cycle counter,

wherein if said cycle counter is less than a first predetermined number and said LPCO means disconnects said compressor, said at least one control processor performs (a)-(c), and if said cycle counter equals said first predetermined number, said at least one control processor declares a malfunction.

5. The controller for a heat pump system of claim 4 wherein said at least one control processor attempts to release said EXV by:

(a1) partially opening said EXV,

(a2) partially closing said EXV, and

(a3) repeating steps (a1) and (a2) a second predetermined number of times.

6. The controller for a heat pump system of claim 4 wherein said at least one control processor operates at default settings by:

(b1) reversing a reversing valve,

(b2) setting said EXV at a first predetermined position,

(b3) setting said indoor fan speed to a first predetermined speed, and

(b4) setting said outdoor fan speed to a second predetermined speed.

7. The controller for a heat pump system of claim 4 wherein said at least one control processor stops said heat pump system if said cycle counter equals said predetermined number and said heat pump system is operating in said cooling mode.

8. The controller for a heat pump system of claim 2 wherein said at least one control processor initiates an emergency heating mode if said cycle counter equals said predetermined number and said heat pump system is operating in said heating mode.

9. The controller for a heat pump system of claim 4 wherein said at least one control processor declares at least one of a lost refrigerant charge malfunction and a stuck EXV malfunction.

10. The controller for a heat pump system of claim 1 wherein, if said differential temperature exceeds said first parameter, said at least one control processor executes a lost refrigerant charge diagnostic procedure that:

(a) determines if said EXV is fully open;

(b) if said EXV is fully open, stops said heat pump system and declares a lost refrigerant charge malfunction.