Patent Application
20120247142
An operational problem that may occur in a heat pump type pool heater (utilizing either a dedicated “heat only” or reversible heating/cooling heat pump circuit) is the generation of high hydraulic pressure spikes occurring upon start-up of the heater after it has been idle (i.e., in the “off” mode) for several days. A sudden increase (“spike”) in hydraulic pressure tends to exceed the setting of the over-pressure sensor of the heater which results in the automatic termination of the operation of the unit's compressor. If this pressure spike-created shutoff occurs three times, the control system locks out the compressor which requires the owner to manually reset the control or call a service technician to place the unit back in operation.
It is believed that this pressure spike problem is caused by too much refrigerant migrating to the relatively small volume water-to-refrigerant heat exchanger used on heat pump pool heaters that fills up the space inside the heat exchanger during the off cycle over an extended time. When the compressor starts, there is not enough gaseous refrigerant between the compressor and expansion device to absorb the sudden increase in pressure produced by the scroll compressor on unit start-up.
This issue is most prevalent on larger size heat pump pool heaters with large evaporator coils and high refrigerant charges relative to the water heater exchanger. Standard receivers help somewhat, but are not that effective and require the addition of costly refrigerant. Historically, the main way to eliminate the nuisance tripping of the pressure sensor is to simply reduce the refrigerant charge of the unit, thereby undesirably lowering the unit's water heating capacity.
As can be seen from the foregoing, a need exists for apparatus that eliminates or at least substantially diminishes this compressor start-up pressure spike problem in a heat pump pool heater or other type of heat pump-based liquid heater. It is to this need that the present invention is primarily directed.
In a representatively illustrated embodiment thereof this invention provides specially designed pressure spike elimination apparatus in a heat pump pool heater to prevent undesirable pressure spikes at the compressor outlet upon system start-up after a substantial downtime period of the heat pump. The representative embodiment of the pressure spike-protected heat pump circuit is illustrated in the accompanying drawings in which:
As schematically depicted in
The heat pump pool heater 10 illustratively comprises a compressor 14, a condenser 16, an expansion valve 18 and an evaporator coil 20 (with an associated fan 22) connected in series as shown by refrigerant tubing 24 through which, during operation of the heater 10, refrigerant flows in the indicated counterclockwise direction. Specifically, the refrigerant sequentially flows from the outlet of the compressor 14, through the condenser 16, through the expansion valve 18, through the evaporator coil 20, and back into the inlet of the compressor 14. As illustrated, a section of the tubing 24 forms a condenser coil 24a within a housing portion 26 of the condenser 16, the coil 24a being immersed in pool water 28 being appropriately pumped through the housing 26 to receive refrigerant heat from the coil 24a.
The pressure spike eliminator structure 12 includes a tubular outer body 30, with closed upper ends 32 and 34, through which a section 24b of the tubing 24 vertically passes, with the tubing 24 being suitably sealed to the body ends 32 and 34. As illustrated, the tubing section 24b extends through an annular cavity 36 disposed in the body 30 and circumscribing the tubing section 24b. Outer body 30 is disposed in the tubing 24 between the discharge of the compressor 14 and the inlet of the condenser 16. While the tubing section 24b is schematically depicted as being an integral portion of the overall tubing 24, it may alternatively be an integral portion of the spike eliminator 12 outer body and may be appropriately secured to facing ends of the tubing 24.
A connector or transfer tube 38 is directly connected at an outlet end thereof to a small inlet opening 40 in the lower end 34 of the outer body 30, and directly connected at an inlet end thereof to a tee portion 42 of the tubing 24 at a location thereon between the outlet of the condenser 16 and the expansion valve 18. Accordingly, the transfer tube 38 communicates the interior of the refrigerant tubing 24 (at the indicated tee location therein) with the cavity 36 in the outer body 30 of the spike eliminator. During operation of the heat pump 10, hot compressor discharge gas flowing through the tubing portion 24b evaporates any liquid refrigerant that may find its way into the body cavity 36. However, during off periods of the heat pump 10, the pressure spike eliminator structure 12 provides the refrigerant system with a “shock absorber” that prevents compressor overpressurization, and attendant unit shutdown, on re-starts of the heater 10 after extended shut-down periods.
As can be envisioned from the circuit diagram of
The pressure spike eliminator apparatus 12 is simple and inexpensive to install, in either the original fabrication of the illustrated refrigerant circuitry or in a retrofit installation, and is highly effective in eliminating the problems associated with system start-up pressure spikes.
This application claims the filing priority benefit of U.S. provisional patent application Ser. No. 61/470,175 filed on Mar. 31, 2011, such prior application being hereby incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61470175 | Mar 2011 | US |
