Systems and Methods for Passive and Active Hybrid Defrost Control for Pool/Spa Heat Pumps

Abstract

Systems and methods for passive and active hybrid defrost control for a pool/spa heat pump are provided. The system monitors the temperature of the evaporator coil of the heat pump and, as required, operates the heat pump in a passive defrost mode if the temperature is less than or equal to a first predetermined temperature value. The system operates the heat pump in an active defrost mode if the temperature of the evaporator coil remains below the first predetermined temperature value and a first time period has expired. The system can stop operation of the active defrost mode when the temperature of the evaporator coil is greater than a second predetermined temperature value. Additionally, the system can stop operation of the passive defrost mode or the active defrost mode upon expiration of a timeout timer.

Description

FIELD OF THE INVENTION

The present disclosure relates to pool and spa equipment. More particularly, the present disclosure relates to systems and methods for passive and active hybrid defrost control for pool/spa heat pumps.

RELATED ART

In the pool and spa industry, proper operation of heating/cooling equipment for pool/spa installations is of significant concern. In the case of heat pumps utilized to heat pool/spa water, effective and efficient defrost control is of particular importance. Specifically, during operation, heat pump pool/spa heaters can form frost on the evaporator coil in environments of low ambient temperature and high humidity. Such frost can reduce the amount of heating capacity and eventually interrupt operation of the heat pump due to low refrigerant pressures. Additionally, heat pumps having evaporator coils constructed of copper tubes and aluminum fins (e.g., fin/tube coils) have large surface areas where frost can form. Further, there are often multiple rows where frost can form.

As a result of frost formation, most heat pumps perform a defrost cycle to clear the evaporation heat exchange surface of frost/ice as ambient temperatures fall and the heat exchanger surface temperature falls below freezing. Heat pumps usually employ one of two different types of defrost cycles: passive defrosting, wherein the ambient temperature being above freezing can be utilized to defrost the heat pump, or active defrosting, wherein the energy from a compressed refrigerant can be utilized to defrost the heat pump. In passive defrosting, the compressor of the heat pump is stopped and the evaporator fan is activated in order to draw ambient air over the evaporator coil and to defrost the coil. In active defrosting, the flow path of refrigerant is reversed to the evaporator and the compressor is activated so that heat is delivered via the refrigerant to the evaporator coil in order to defrost it. Notably, passive defrosting requires significantly less electrical energy than active defrosting. However, known existing pool/spa heat pumps do not employ both methods of defrosting (passive and active) in order to efficiently and effectively defrost the evaporator coil while conserving electrical energy consumption. Accordingly, the systems and methods disclosed herein address the foregoing and other needs.

SUMMARY

The present disclosure relates to systems and methods for passive and active hybrid defrost control for a pool/spa heat pump. The system monitors the temperature of the evaporator coil of the heat pump and, as required, operates the heat pump in a passive defrost mode if the temperature is less than or equal to a first predetermined temperature value. The system operates the heat pump in an active defrost mode if the temperature of the evaporator coil remains below the first predetermined temperature value and a first time period has expired. The system can stop operation of the active defrost mode when the temperature of the evaporator coil is greater than a second predetermined temperature value. Additionally, the system can stop operation of the passive defrost mode or the active defrost mode upon expiration of a timeout timer.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be apparent from the following Detailed Description, taken in connection with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a system for passive and active hybrid defrost control for a pool/spa heat pump, in accordance with the present disclosure;

FIGS. 2-5 are flowcharts illustrating steps carried out by the system of FIG. 1.

DETAILED DESCRIPTION

The present disclosure relates to systems and methods for passive and active hybrid defrost control for a pool/spa heat pump, as described in detail below in connection with FIGS. 1-5.

FIG. 1 is a diagram illustrating a system for passive and active hybrid defrost control for a pool/spa heat pump in accordance with the present disclosure, indicated generally at 10. The system 10 includes a controller 12 for controlling operation of a pool/spa heat pump 16, and passive/active hybrid defrost control logic 14 executed by the controller 12 and selectively operating the heat pump 16 to defrost the heat pump 16 using both passive and active defrost techniques. Specifically, as will be discussed in greater detail in connection with FIGS. 2-5, the control logic 14 controls operation of the compressor and the fan of the heat pump 16 (and associated timers and display features) in order to effectively and efficiently defrost the heat pump 16 using both passive and active defrost techniques.

The controller 12 could form part of the heat pump 16 (e.g., it could be implemented as a controller board having an associated processor and memory and positioned within the heat pump 16), or it could be part of a separate control device in communication with the heat pump 16, e.g., a pool/spa control system 18 that is in communication with the heat pump 16 (e.g., via a communications network 22). The network 22 could be a wired communications network (e.g., an RS-485 serial communications network, an Ethernet network, etc.), a wireless communications network (e.g., a WiFi network, a Bluetooth network, a cellular data network, a ZigBee network, a mesh wireless network, etc.), the Internet, or some other type of network. Further, the control logic 14 could be stored on and executed by a cloud-based pool/spa control system 20 which is in communication with, and remotely controls operation of, the heat pump 16 via the network 22. Optionally, one or more user devices (e.g., a cellular phone, a tablet computer, a laptop computer, etc.) could be in communication with one or more of the heat pump 16, the pool/spa control system 18, or the cloud-based pool/spa control system 20. The control logic 14 could be embodied as non-transitory, computer-readable instructions (e.g., firmware) stored on a computer-readable medium (e.g., a memory) of the controller 12 and executed by a processor (e.g., microprocessor, microcontroller, etc.) of the controller 12. The control logic 14 could be programmed in any suitable high- or low-level programming language, such as C, C++, C#, Python, assembly language, or any other suitable programming language.

FIGS. 2-5 are flowcharts illustrating steps carried out by the system of FIG. 1. Specifically, FIGS. 2-5 illustrate steps carried out by the control logic 14 to provide for passive and active hybrid defrost of the heat pump 16 in accordance with the present disclosure. Beginning in step 30 of FIG. 2, the control logic 14 obtains a defrost temperature from memory. Such defrost temperature could be a preset temperature stored in memory, or a dynamic (varying) temperature. In step 32, a determination is made as to whether defrost is “busy” (e.g., whether the heat pump 16 is currently performing a defrost operation). If a positive determination is made, step 34 occurs. Otherwise, step 36 occurs, wherein a determination is made as to whether the temperature of the evaporator coil of the heat pump 16 is lower than or equal to a first preset temperature value (e.g., less than or equal to 29 degrees fahrenheit, or less than a range of 22 to 32 degrees fahrenheit). The evaporator coil temperature could be measured using a coil temperature sensor in communication with the controller 12. If a negative determination is made, step 34 occurs. Otherwise, step 37 occurs, wherein a defrost busy flag is set to active. Then, in step 39, the defrost mode is set to passive, and in step 40, the heat pump 16 is commanded to begin defrosting the evaporator coil using passive defrosting (e.g., using ambient air defrost the evaporator coil by commanding the fan of the heat pump to run at a pre-defined speed and for a pre-defined period of time in order to defrost the evaporator coil).

In step 34, a determination is made as to whether the heat pump 16 is currently performing a defrost operation. If a negative determination is made control passes to branch “A” described in greater detail in FIG. 3. Otherwise, if a positive determination is made, step 42 occurs, wherein a determination is made as to whether the current defrost mode is passive. If a negative determination is made, control passes to branch A (FIG. 3). Otherwise, step 44 occurs, wherein a determination is made as to whether a passive defrost timer has elapsed (e.g., whether a pre-defined period of time (e.g., 3-20 minutes) during which a passive defrost operation occurred has elapsed). If a negative determination is made, control passes to branch A (FIG. 3). Otherwise, step 46 occurs, wherein a determination is made as to whether the evaporator coil temperature is greater than a second predetermined temperature (e.g., greater than 42 degrees fahrenheit, or greater than a range of 40-50 degrees fahrenheit). If a negative determination is made, step 48 occurs, wherein the defrost mode is set to active, followed by step 50 wherein active defrosting of the evaporator coil occurs (e.g., using the energy from a compressed refrigerant by controlling operation of the compressor of the heat pump). In such circumstances, the reversing valve of the heat pump 16 is reversed and the compressor is operated in order to draw hot refrigerant from the compressor to the evaporator coil in order to defrost the coil. Then, control passes to branch A (FIG. 3). If a positive determination is made in step 46, step 52 occurs, wherein the defrost “busy” flag is cleared. Then, in step 54, the current defrost operation is terminated.

Turning to FIG. 3, control branches “A” and “B” of the control logic 14 are described in greater detail. Branch A begins in step 60, wherein a determination is made as to whether defrost is busy, e.g., whether the heat pump 16 is currently performing a defrost operation. If a negative determination is made, control passes to branch B. Otherwise, step 62 occurs, wherein a determination is made as to whether the current defrost mode is set to active defrosting. If a negative determination is made, control passes to branch B. Otherwise, step 64 occurs, wherein a determination is made as to whether an active defrost timer has elapsed (e.g., whether a pre-defined period of time (e.g., 3-10 minutes) during which an active defrost operation occurred has elapsed). If a negative determination is made, control passes to branch B. Otherwise, step 66 occurs, wherein a determination is made as to whether the temperature of the evaporator coil is greater than 42 degrees fahrenheit or greater than a range of 40-50 degrees fahrenheit. If a negative determination is made, step 68 occurs, wherein the active defrost timer is reset, and then control passes to branch B. Otherwise, step 70 occurs, wherein the defrost flag is cleared. Then, step 72 occurs wherein the current defrost cycle is ended, and control passes to branch B.

Branch B begins in step 74, wherein a determination is made as to whether defrost is busy, e.g., whether the heat pump is currently performing a defrost operation. If a negative determination is made, control returns back to step 30 of FIG. 2. Otherwise, step 76 occurs, wherein a determination is made as to whether any errors have occurred. If a positive determination is made, control returns to step 30 of FIG. 2. Otherwise, step 78 occurs, wherein a determination is made as to whether a timeout has expired. If a negative determination has been made, control returns to step 30 of FIG. 2. Otherwise, step 80 occurs, wherein the defrost flag is cleared. Then, step 82 occurs, wherein the current defrost operation is terminated, and then control returns back to step 30 of FIG. 1.

FIG. 4 illustrates further steps of the control logic 14 for initiating a defrost operation. In step 90, a determination is made as to whether the defrost mode is passive. If a positive determination is made, step 96 occurs, wherein the compressor of the heat pump (“Comp”) and a display associated with the compressor (“Comp LCD”) are turned off. Then, step 98 occurs, wherein the evaporator fan of the heat pump (“Fan”) and a display associated with the evaporator fan (“Fan LCD”) are turned on. Then, step 100 occurs, wherein the timeout timer, the passive defrost timer, and the active defrost timer are each reset. Finally, step 102 occurs, wherein the defrost “ON” indication (e.g., on a display of the heat pump) is turned on.

In the event that a determination is made in step 90 that the defrost mode is not passive (e.g., the defrost mode is active), step 92 occurs, wherein the evaporator fan (“Fan”) and the display associated with the evaporator fan (“Fan LCD”) are turned off. Then, step 94 occurs, wherein the compressor of the heat pump (“Comp”), a display associated with the compressor (“Comp LCD”), and the reversing valve (“HG_Rev”) are turned on. Control then passes to steps 100 and 102, discussed above.

FIG. 5 illustrate further steps of the control logic 14 for terminating (ending) a defrost operation. In step 110, a determination is made as to whether a display menu (e.g., a menu associated with the heat pump 16) is set to zero. If a positive determination is made, step 112 occurs, wherein the system returns to normal operation (e.g., the system returns to normal heating operation or to a prior operational status prior to the initiation of a defrost operation). In step 114, the timeout timer, passive defrost timer, and active defrost timer are each reset. Next, in step 116, the reversing valve (“HG_Rev”) is turned off. Finally, step 118 occurs, wherein the defrost “ON” notification is cleared.

It has been found that the passive and active hybrid defrost systems and methods of the present disclosure are particularly effective for defrosting heat pump evaporator coils when the ambient temperature is below 50 degrees fahrenheit and with ambient relative humidity levels up to 95%. Additionally, it has been found that the passive and active hybrid defrost systems and methods of the present disclosure are particularly effective in defrosting microchannel evaporator coils that have thin aluminum channels and fins. It is further noted that the control logic 14 could be supplemented with logic to predict the need for either passive or active defrosting based on parameters such as location and season (e.g., in the fall in Phoenix, AZ the usage of passive versus active defrosting would differ than the spring in Florida, due to differences in ambient temperatures and relative humidities). Additionally, the systems and methods of the present disclosure could allow a user to lock the heat pump in either passive defrost or active defrost modes (where only one mode is used for defrosting).

Having thus described the system and method in detail, it is to be understood that the foregoing description is not intended to limit the spirit or scope thereof. It will be understood that the embodiments of the present disclosure described herein are merely exemplary and that a person skilled in the art may make any variations and modification without departing from the spirit and scope of the disclosure. All such variations and modifications, including those discussed above, are intended to be included within the scope of the disclosure.

Claims

1. A system for passive/active hybrid defrosting of a heat pump, comprising: a controller in communication with a heat pump; anda memory storing control logic executed by the controller, the control logic causing the controller to:determine a temperature of an evaporator coil of the heat pump;operate the heat pump in a passive defrost mode if the temperature of the evaporator coil is less than or equal to a first predetermined temperature value; andoperate the heat pump in an active defrost mode if the temperature of the evaporator coil remains below the first predetermined temperature value and a first time period has expired.

2. The system of claim 1, wherein the control logic causes the controller to operate the heat pump in the passive defrost mode for the first time period.

3. The system of claim 2, wherein the control logic causes the controller to stop operation of the passive defrost mode when the first time period has elapsed and the temperature of the evaporator coil remains below the first predetermined temperature value.

4. The system of claim 1, wherein the control logic causes the heat pump to stop operation of the active defrost mode when the temperature of the evaporator coil is greater than a second predetermined temperature value.

5. The system of claim 1, wherein the control logic causes the controller to operate the heat pump in the active defrost mode for a second time period.

6. The system of claim 5, wherein the control logic causes the controller to stop operation of the active defrost mode if the temperature of the evaporator coil is greater than the second predetermined temperature value.

7. The system of claim 1 where the control logic causes the controller to stop operation of the passive defrost mode or the active defrost mode upon expiration of a timeout timer.

8. The system of claim 1, wherein the first predetermined temperature value is 29 degrees fahrenheit.

9. The system of claim 1, wherein the first predetermined temperature value falls in a range of 22-32 degrees fahrenheit.

10. The system of claim 1, wherein the second predetermined temperature value is 42 degrees fahrenheit.

11. The system of claim 1, wherein the second predetermined temperature value falls in a range of 40-50 degrees fahrenheit.

12. The system of claim 1, wherein the heat pump is operated in the passive defrost mode by turning off a compressor of the heat pump and turning on a fan of the heat pump.

13. The system of claim 1, wherein the heat pump is operated in the active defrost mode by turning off a fan of the heat pump and turning on a compressor of the heat pump.