Geothermal heat pump freeze protection with electric heater staging

Abstract

A method of auxiliary heat staging in a heat pump system having a geothermal water source or open loop. The method includes receiving a demand for heating in the heat pump system, receiving a temperature signal indicative of a temperature associated with a liquid in the geothermal loop, determining if the temperature associated with the liquid in the geothermal loop is lower than a first selected threshold. If the temperature is lower than the first selected threshold, then operating the heat pump system and the auxiliary heat at an increased capacity.

What is claimed is: 
     
         1 . A heat pump system having a geothermal ground source loop with auxiliary heat staging, the heat pump system comprising:
 a geothermal loop circulating a liquid in the geothermal loop in a first heat exchange relationship with geothermal heat;   a refrigerant circuit for circulating refrigerant having a plurality of flowpaths in the heat pump system;   a first heat exchanger being at least disposed in the refrigerant circuit for circulating the refrigerant, and at least disposed in a path of ambient air or fluid of a facility, the refrigerant in a second heat exchange relationship with the ambient air or fluid;   a second heat exchanger being disposed in the refrigerant circuit for circulating the refrigerant, and disposed in fluid communication with the geothermal loop, the refrigerant in a third heat exchange relationship with the liquid in the geothermal loop;   at least one compressor connected into the refrigerant circuit for compressing the refrigerant from its inlet pressure to its discharge pressure under conditions of operation of the refrigerant circuit;   at least one expansion device connected at the inlet of a heat exchanger in which the refrigerant is being vaporized;   at least one valve disposed in the refrigerant circuit and operably selecting one or more flow paths of the plurality of flowpaths of the refrigerant circuit including the first heat exchanger, second heat and direction of flow of the refrigerant therethrough for selecting a particular mode of operation of the heat pump system;   an auxiliary heater disposed in the ambient air of the facility and operable to add heat to the ambient air under selected conditions;   a temperature sensor a disposed at the geothermal loop, the temperature sensor operable to provide a temperature signal indicative of a temperature associated with the liquid in the geothermal loop; and   a controller operable to receive the temperature signal from the temperature sensor and control activation of the auxiliary heater responsive to a demand for heating in at least a heating mode and a under selected conditions associated with the geothermal loop.   
     
     
         2 . The heat pump system of  claim 1 , wherein the at least one valve is a reversing valve and is included in said refrigerant circuit for effecting operation respectively in at least one of the heating mode a cooling mode and a dehumidification mode. 
     
     
         3 . The heat pump system of  claim 1 , further including a thermostat, the thermostat providing a signal to the controller indicative of at least the demand for heating in the heating mode. 
     
     
         4 . The heat pump system of  claim 1 , further including a circulation fan or a pump for the ambient air or fluid associated with the first heat exchanger for circulating ambient air or fluid past the first heat exchanger to facilitate refrigerant to ambient air or fluid heat exchange. 
     
     
         5 . The heat pump system of  claim 1 , wherein the controller determines if the temperature associated with the liquid in the geothermal loop is lower than a first selected threshold, if the temperature is lower than the first selected threshold, then the controller operates the heat pump system and the auxiliary heat at an increased capacity. 
     
     
         6 . The heat pump system of  claim 5 , wherein the controller determines if the temperature associated with the liquid in the geothermal loop is lower than a second selected threshold, then the controller operates the heat pump system and the auxiliary heater at, at a further increased capacity. 
     
     
         7 . The heat pump system of  claim 5 , further including determining if the temperature associated with the liquid in the geothermal loop increases above a third selected threshold, if the temperature associated with the liquid in the geothermal loop is greater than the third selected threshold, then operating the heat pump system with the auxiliary heat at, at least the increased capacity. 
     
     
         8 . The heat pump system of  claim 5 , wherein the first selected threshold is selected for the temperature of the liquid in the geothermal loop at a temperature far enough away from a freezing temperature of the liquid to permit the heat pump system to partially extract the geothermal heat from the geothermal loop. 
     
     
         9 . The heat pump system of  claim 8 , wherein the first selected threshold is established at a temperature based at least in part on the liquid in the geothermal loop and a particular application. 
     
     
         10 . The heat pump system of  claim 6 , wherein the second selected threshold is selected for the temperature of the liquid in the geothermal loop at temperature to avoid a freezing temperature, nor nearing a freezing temperature, of the liquid to permit the heat pump system to rest the geothermal loop. 
     
     
         11 . The heat pump system of  claim 10 , wherein the second selected threshold is established at a temperature of based at least in part on the liquid in the geothermal loop and a particular application. 
     
     
         12 . The heat pump system of  claim 7 , wherein the third selected threshold is selected for the temperature of the liquid in the geothermal loop at temperature far enough away from a freezing temperature of the liquid to permit the heat pump system to extract the geothermal heat from the geothermal loop. 
     
     
         13 . A method of auxiliary heat staging in a heat pump system having a geothermal loop, the method comprising:
 receiving a demand for heating associated with a facility in the heat pump system;   receiving a temperature signal indicative of a temperature associated with a liquid in the geothermal ground source or water well loop;   determining if the temperature associated with the liquid in the geothermal loop is lower than a first selected threshold; and   if the temperature is lower than the first selected threshold, then operating the heat pump system an auxiliary heater at, at least, an increased or higher capacity based on the demand.   
     
     
         14 . The method of auxiliary heat staging in a heat pump system of  claim 13 , wherein the demand is generated by a thermostat in the facility that measures the temperature of the facility and determines that the temperature measured is at or below a selected threshold. 
     
     
         15 . The method of auxiliary heat staging in a heat pump system of  claim 13 , wherein the first selected threshold is selected for the temperature of the liquid in the geothermal loop at a temperature far enough away from a freezing temperature of the liquid to permit the heat pump system to extract heat from the geothermal loop. 
     
     
         16 . The method of auxiliary heat staging in a heat pump system of  claim 15 , wherein the first selected threshold is established at a temperature based at least in part on the liquid in the geothermal loop and a particular application. 
     
     
         17 . The method of auxiliary heat staging in a heat pump system of  claim 13 , further including determining if the temperature associated with the liquid in the geothermal loop is lower than a second selected threshold; and
 if the temperature is lower than the second selected threshold, then operating the heat pump system and the auxiliary electric heater at, at least, at a further higher capacity than the increased capacity.   
     
     
         18 . The method of auxiliary heat staging in a heat pump system of  claim 17 , wherein the second selected threshold is selected for a temperature of the liquid in the geothermal loop at temperature to avoid a freezing temperature of the liquid to permit the heat pump system to rest the geothermal loop. 
     
     
         19 . The method of auxiliary heat staging in a heat pump system of  claim 16 , wherein the second selected threshold is established at a temperature based at least in part on the liquid in the geothermal loop and a particular application. 
     
     
         20 . The method of auxiliary heat staging in a heat pump system of  claim 13 , further including determining if the temperature associated with the liquid in the geothermal loop increases above a third selected threshold, if the temperature associated with the liquid in the geothermal loop is greater than the third selected threshold, then operating the heat pump system with the auxiliary heat at the increased capacity.