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.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/837,486, filed Apr. 23, 2019, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present disclosure relates to control of a geothermal system. More particularly, to a geothermal heat pump device having circulation control of the ground circulating loop in a geothermal system and an auxiliary heating source staging.

Heat pumps are used in a variety of settings, for example, in HVAC systems that provide a desired air temperature in a facility. Such heat pumps commonly include a compressor, evaporator, expansion valve, and condenser. The heat pumps input work to the refrigerant, e.g., by driving the compressor, thereby enabling the refrigerant to extract heat from a source and reject it into a conditioned space, and conversely extract heat from a conditioned space and reject it into a heat sink.

In geothermal applications the “outside” heat exchanger includes a buried loop or well for closed loop and open loop systems respectively. After refrigerant expanded by the heating expansion valve, heat is exchanged with water of the well, heating the refrigerant and cooling the water in the loop or well. In the in the geothermal well circulation circuit, a circulating liquid such as water flows through a circulation path, and exchanges heat with the ground ambient. In the heat pump device at the contact point between the circulating water from the geothermal well, the heat of the circulating liquid transfers the thermal energy to the circulating liquid of the refrigerant by heat exchange. Since circulating fluid or air from the building extracts heat from the refrigerant then circulates in the building to be heated, the interior of the building is heated using this thermal energy.

However, in an environment where the temperature drops below the freezing point, extended periods of low geothermal loop temperatures for example, resulting from high heating loads, or undersized geothermal loops, the circulating liquid circulating in the source side circulation circuit may freeze and the geothermal system may not function properly. As a countermeasure against potential freezing, it is sometimes necessary to take measures to replace the water content of the circulating liquid with a liquid having a lower freezing point such as an antifreeze solution. Other countermeasures include sensors and freeze protections that monitor the temperature of the refrigerant circuit and/or loop fluid circuit and disable the geothermal loop to avoid excessively cooling the water. Other techniques are to automatically heat the water in the geothermal loop using stored heat or heating elements, or even temporarily reversing the operation of the heat pump. Yet another technique is to employ an “off” time, automatic/timed staging of auxiliary heat, or scheduled rest time for the geothermal loop to permit the geothermal loop to recover. Another approach is to never stage down auxiliary heat; utilizing supplemental heating to increase heating capacity, thus allowing longer time between heat pump start-ups. Operating on supplemental heating, or turning it on prematurely is generally much more expensive than operation of the ground source heat pump alone.

Accordingly, it is desirable to provide an uncomplicated method for ensuring geothermal loop freeze protections while upstaging utilization of supplemental heating in advance to improve efficiency under selected conditions and/or to keep equipment in operation trouble free.

SUMMARY

According to one embodiment described herein is an A method of auxiliary electric heat staging in a heat pump system having a geothermal loop. The method includes receiving a demand for heating in the heat pump system or building thermostat, 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 a reduced loading or just heat pump only with no auxiliary heating based on the heat demand. The method also includes determining if the temperature associated with the liquid in the geothermal loop is lower than a second selected threshold. If the temperature is lower than the second selected threshold, then operating the heat pump system and the auxiliary electric heater at full capacity and then shut down the whole system when the demand is satisfied.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the at least one valve is a reversing valve and is included in said refrigerant circuit for effecting operation respectively in the heating mode and in a cooling mode.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include a thermostat, the thermostat providing a signal to the controller indicative of at least the demand for heating in the heating mode.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include a circulation fan or pump for the ambient air or fluid associated with the first heat exchanger for circulating ambient air past the first heat exchanger to facilitate refrigerant to ambient air or hydronic fluid heat exchange.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that 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.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that 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 electric heater at a further increased capacity.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the 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.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that 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.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the first selected threshold is established at a user selected temperature based at least in part on the fluid used. In one example 45° F. is used.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the second selected threshold is selected for the 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. This can be done by increasing the capacity using auxiliary heating to reach the desired building temperature faster, allowing the loop to rest.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that the second selected threshold is established at a user selected temperature based at least in part on the fluid used. In one example a temperature of 34° F. is used.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that 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 a reduced capacity.

In addition to one or more of the features described above, or as an alternative, further embodiments of the system may include that 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 partially extract the geothermal heat from the geothermal loop.

Also disclosed herein in another embodiment is a method of auxiliary electric heat staging in a heat pump system having a geothermal loop. The method includes 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 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 auxiliary electric heater at an increased capacity.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include 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 a further increased capacity including full capacity.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that 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.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that 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 heat from the geothermal loop.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that the first selected threshold is established at a user selected temperature based at least in part on the fluid used. In one example 45° F. is used.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that 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.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that the second selected threshold is established at a user selected temperature based at least in part on the fluid used. In one example 34° F. is used.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include 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.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that the third 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 heat from the geothermal loop.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that the circulation of a heat exchange fluid through a heat exchanger is stopped when too much heat is removed from the geothermal loop connected in a heat exchange relationship with the heat exchange fluid, as determined by a sensed temperature of the liquid in the geothermal loop.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that the geothermal loop may be at least one of a closed circuit loop or an open circuit well or pond.

In addition to one or more of the features described above, or as an alternative, further embodiments of the method of auxiliary electric heat staging may include that the thresholds are based on whether the geothermal loop is a closed circuit loop or an open circuit well or pond.

Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed disclosure. For a better understanding of the disclosure with the advantages and the features, refer to the description.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts an example of a heat pump system in accordance with an exemplary embodiment; and

FIG. 2 depicts a simplified flowchart of method of auxiliary electric heat staging in a heat pump system having a geothermal loop in accordance with an embodiment.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It should nevertheless be understood that no limitation of the scope of this disclosure is thereby intended. The following description is merely illustrative in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the term controller refers to processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, an electronic processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable interfaces and components that provide the described functionality.

Additionally, the term “exemplary” is used herein to mean “serving as an example, instance or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms “at least one” and “one or more” are understood to include any integer number greater than or equal to one, i.e. one, two, three, four, etc. The terms “a plurality” are understood to include any integer number greater than or equal to two, i.e. two, three, four, five, etc. The term “connection” can include an indirect “connection” and/or a direct “connection”.

In general, embodiments herein relate to an application of a method and/or system for staging auxiliary heat (commonly electric coil) in a heat pump system having a geothermal loop or water source heat pump. Demand for upstaging and activating supplemental auxiliary heating is configured to be independent of building load demand to ensure continual operation of the system. Activating auxiliary electric heat earlier than demand requests facilitates additional rest time for the geothermal loop or well by increasing the time between cycles. Upstaging shall be done with an algorithm based on entering water temperature of medium in the closed loop and/or facility demand.

FIG. 1 illustrates an exemplary heat pump system 100, according to an embodiment. The heat pump system 100 having an indoor portion 102 positioned inside a facility 103 and an outdoor portion 104 positioned outside the facility 103; however, in various embodiments, the heat pump 100 may instead be housed in a single casing and/or disposed partially inside and partially outside, or either completely inside or outside the facility 103. FIG. 1 may illustrate default or “normal” operation of the heat pump 100, with the heat pump 100 being configured to heat the facility 103; however, it will be readily appreciated that the heat pump system 100 can be reversed to cool the facility 103. It should be appreciated that while the heat pump system 100 is depicted as a split system with separated indoor portions 102 and outdoor portions 104, such description is merely illustrative. The heat pump system 100 could also be a split system of different packaging or integration, stand-alone packaged product, or even a fully contained roof-top type of configuration. In these other configurations the indoor portion and the outdoor portion or at least parts thereof may be integrated.

The heat pump system 100 includes a compressor 106, which may be located, for example, in the outdoor portion 104. The compressor 106 includes an inlet 107a configured to receive a lower-pressure refrigerant and an outlet 107b configured to discharge a higher-pressure refrigerant. The refrigerant can be or include, without limitation, Freon, R134a, propane, butane, methane, R410A, carbon dioxide, nitrogen, argon, other organic or HCFC refrigerants, combinations thereof, or the like.

The compressor 106 can be any suitable single or multistage compressor, for example, a screw compressor, reciprocating compressor, centrifugal compressor, scroll compressor axial-flow compressor, or the like. The compressor 106 may also be representative of multiple discrete or cooperative compressors, or be inverter driven/variable speed with modulating output. Further, the compressor 106 may include a motor (not shown), which may be electrically powered to drive the compressor 106. In some embodiments, however, other energy sources may be employed to drive the compressor 106, such as, for example, natural gas. The compressor 106 may be “energized” and “de-energized,” for example, by controlling the power to the motor. In a single-stage embodiment of the compressor 106, power can be provided to the motor, which in turn, supplies mechanical energy to the compressor 106, thereby “energizing” the compressor 106. Further, power can be turned off to the motor, or the motor can be mechanically decoupled from the compressive portions of the compressor 106, such that the compressor 106 is “de-energized” and therefore ceases to compress refrigerant. In multi-stage or multi-unit embodiments of the compressor 106, the compressor 106 can be “de-energized” by stopping the supply of mechanical energy to one, some, or all of the compression stages (or units) of the compressor 106.

The heat pump 100 also includes a first heat exchanger 108, which may be disposed in the indoor portion 102, and may be fluidly coupled to the compressor 106. The first heat exchanger 108 may be any suitable type of heat exchanger configured to transfer heat between a refrigerant and air or another medium (e.g., water). For example, the first heat exchanger 108 may include one or more coils of thermally conductive material, such as copper, aluminum, alloys thereof, combinations thereof, or the like. In other embodiments, the first heat exchanger 108 may be or additionally include a shell-and-tube heat exchanger, a printed circuit heat exchanger, a plate-fin heat exchanger, combinations thereof, or the like. The air (or other medium) may be motivated past the first heat exchanger 108 via a blower 110, which may be any suitable air moving device, including one or more axial, radial, or centrifugal fans, blowers, pumps, compressors, combinations thereof, or the like.

The heat pump system 100 may further include at least one expansion device, for example, an indoor expansion device 112 positioned in the indoor portion 102, and an outdoor expansion device 114 positioned in the outdoor portion 104. At least one of the indoor and outdoor expansion devices 112, 114 may be fluidly coupled to the first heat exchanger 108. The expansion devices 112, 114 may each be or include one or more types of thermal expansion valves (TEVs), Joule-Thomson valves, electronic expansion valves (EXVs) or the like. In other embodiments, one or both of the expansion devices 112, 114 may be a turbine or other type of expander. Although not shown, the heat pump system 100 may include one or more valves and/or bypass lines to enable bypass of the indoor and/or outdoor expansion devices 112, 114, for example, according to whether the heat pump 100 is set to cool a facility or heat a facility, as will be described in greater detail below.

The heat pump system 100 may also include a second heat exchanger 116 fluidly coupled at least one of the indoor and outdoor expansion devices 112, 114. In an embodiment, the second heat exchanger 116 may be disposed about the outer extent of the outdoor portion 104 of the heat pump system 100, as schematically depicted in FIG. 1. However, in other embodiments, the second heat exchanger 116 may be disposed in any location within, around, and/or proximal to the outdoor portion 104. The second heat exchanger 116 may be any suitable type of heat exchanger configured to transfer heat between a refrigerant and air or another medium (e.g., water for the geothermal loop). For example, the second heat exchanger 116 may include one or more coils of thermally conductive material, such as copper, aluminum, alloys thereof, combinations thereof, or the like. In some embodiments, the second heat exchanger 116 may be or additionally include a shell-and-tube heat exchanger, a printed circuit heat exchanger, a plate-fin heat exchanger, twisted tube coaxial, combinations thereof, or the like.

The heat pump 100 may include a pump to urge or otherwise motivate the liquid past (or through) the second heat exchanger 116. The pump 150 may include a motor 120 and one or more blades or impeller (not shown), and may be, in at least one embodiment, positioned in line with the geothermal loop 152. The pump may be configured to the fluid into and through the second heat exchanger 116, returning it to the loop 152 as shown.

The heat pump system 100 may also include an accumulator 128 disposed upstream from the compressor 106. The accumulator 128 may be a pressurized vessel configured to store extra refrigerant, which may provide refrigerant inventory control in the heat pump system 100 and/or may store excess refrigerant. The accumulator 128 may be in line with the compressor 106, or may be selectively branched off upstream of the compressor inlet 107a, for example, by a three-way valve (not shown). The heat pump 100 may further include a muffler 130 to attenuate the propagation of noise from the compressor 106. The muffler 130 may be any suitable noise-attenuating device. Further, one or more service valves 132 may be disposed, from a fluid-flow standpoint, between the compressor 106 and the first heat exchanger 108. The service valve 132 may be or include one or more gate valves, ball valves, check valves, or any other valves which are operable to facilitate decoupling the indoor and outdoor portions 102, 104 for maintenance, repair, replacement, installation.

The heat pump 100 may also include a reversing valve 134, according to an embodiment. The reversing valve 134 may be positioned in the outdoor portion 104 and, from a fluid flow standpoint, between the compressor 106 and the first heat exchanger 108 and between the second heat exchanger 116 and the compressor 106. The reversing valve 134 may include two flowpaths therethrough: a first flowpath 136 and a second flowpath 138. In one or more embodiments, the first and second flowpaths 136, 138 may be discrete, preventing fluid flowing through the first flowpath 136 from mixing with fluid flowing through the second flowpath 138 and vice versa. In other embodiments, some intermixing between the first and second flowpaths 136, 138 may be allowed. The flowpaths 136, 138 selectable to implement a cooling mode, a heating mode, or a dehumidification mode for the heat pump system 100.

Further, the reversing valve 134 may have a default state and an energized state. For example, FIG. 1 may illustrate the default state of the reversing valve 134. In the illustrated embodiment, when in the default state, the reversing valve 134 may be configured such that the first flowpath 136 fluidly connects the compressor outlet 107 b (e.g., via the muffler 130) to the first heat exchanger 108 and the second flowpath 138 fluidly connects the second heat exchanger 116 to the compressor inlet 107 a (e.g., via the accumulator 128).

The heat pump system 100 may also include an auxiliary heater 139 positioned in the indoor portion 102, proximal to the blower 110. The auxiliary heater 139 may be an electrical resistance or inductive heater, hydronic coil, a gas heater or furnace, a combination thereof, or the like. The auxiliary heater 139 may be configured to provide supplemental heat for the air moved into the facility 103 by the blower 110 during heating mode or when the geothermal loop 152 is either not operational (e.g., freeze condition).

The heat pump 100 may also include a controller 140 and one or more sensors such as a temperature sensor 142, which may be coupled together such that the controller 140 is configured to receive a signal from the temperature sensor 142. The temperature sensor 142 may be a thermistor, thermocouple, thermostat, infrared sensor, combinations thereof, or the like, and may be in contact with or disposed closely proximal to the second heat exchanger 116 so as to gauge a temperature of the second heat exchanger 116. The controller 140 and the temperature sensor 142 may be disposed within the outdoor portion 104, or outside thereof.

The controller 140 may be or include one or more programmable logic controllers and may be additionally coupled with the compressor 106, reversing valve 134, fan 118, auxiliary heater 139, and any other components of the heat pump 100 so as to communicate therewith. The controller 140 may be configured to receive an input from the temperature sensor 142 and provide output signals to one or more of the compressor 106, reversing valve 134, fan 118, and auxiliary heater 139. Such output signals may control whether each component is energized or de-energized.

In operation, the controller 140 is configured to control the heat pump system 100 in a manner to address and provide for a calls for heating or cooling of the facility, e.g., the building space to be conditioned. A thermostat 160 measures the temperature, humidity and the like in the conditioned space of the facility and calls for heating or cooling accordingly.

When the heat pump system 100 is providing cooling under some conditions (extreme cold, high heating load, undersized geothermal loop, and the like) the geothermal loop 152 can experience temperatures that may cause the liquid circulating in the loop 152 to freeze and the geothermal system may not function properly. As a countermeasure against potential freezing, sensors and freeze protection algorithms are employed that monitor the temperature of the geothermal loop and disable the geothermal loop to avoid excessively cooling the water. One technique employed is an “off” time or rest time for the geothermal loop 152 to permit the geothermal loop to recover to a higher temperature. However, during such a rest time or after a period of no heating, the supplemental auxiliary heater 139 is typically activated and required to operate at its highest stage levels to satisfy the demand for heating in the facility 103. Commonly, this heating is achieved by not down-staging the auxiliary electric heat 139 and to finish/satisfy the heating call employing the highest electric heat stage from the auxiliary electric heater 139. Alternatively, the thermostat 160 may determine that the heating demand is not being satisfied within a selected time period and determine that the geothermal loop is insufficient to/incapable of satisfying the heating demand. As a result, a rest/off time is employed to permit the geothermal loop to recover.

In an embodiment, the controller 140 or the thermostat 160 employs and executes a methodology to enable down-staging of the electric auxiliary heater 139 to reduce energy consumption and/or help satisfy the temperature demand of 103. The algorithm is based upon demand (heating) and temperature of the liquid in the geothermal loop 152. In the described embodiments the temperature of the liquid (typically water and antifreeze mixture) in the geothermal loop 152 is monitor Temperature sensor 142 monitors the entering water temperature. The temperature of the liquid in the geothermal loop is compared with a first selected temperature threshold. If the temperature of the liquid in the geothermal loop decreases below the first selected threshold, the auxiliary electric heater is activated (if not operating) and/or operated at an increased capacity, but not necessarily a maximum capacity output for a selected duration. If the temperature of the liquid in the geothermal loop decreases to below a second selected threshold temperature (e.g., near the freeze temp), the methodology causes the auxiliary electric heater to operates at a further increased capacity up to and including at full stage or power to provided heating for the facility 103 and satisfy the heating demand Thereby permitting the geothermal loop an opportunity to rest and recover to an operable temperature and state. Advantageously the electric heat up/down-staging algorithm of the described embodiments reduces energy consumption may be readily automatically controlled and requires minimal user interaction and configuration. The described embodiments also aid in continual operation of the system to help ensure temperature demand is met in the facility.

Turning now to FIG. 2 depicting the method 200 of staging auxiliary heating in a geothermal heat pump system 100 having a geothermal loop 152. The method 200 initiates with process step 205 including receiving a demand for heating in the heat pump system 100. The demand is usually generated by a thermostat 160 in the facility 103 that measures the temperature and 160, or in combination with 160 and 140, determines that the measured temperature is at or below a selected threshold. At process step 210, the method 200 continues with receiving a temperature signal indicative with a temperature associated with a liquid in the geothermal loop 152. It is then determined if the temperature associated with the liquid in the geothermal loop 152 is lower than a first selected threshold as depicted at process step 215. In an embodiment, the first selected threshold is selected for a temperature of the liquid in the geothermal loop 152 at temperature far enough away from the freezing temperature to permit the heat pump system to partially extract heat from the geothermal loop 152. In one embodiment the first selected threshold is established at a temperature of 45° F. Though other temperatures are possible for the first selected threshold. In an embodiment, the thresholds are configurable as a function of the geothermal loop 152 or well design as well as the fluid employed. An installer can configure the freeze limits as part of system commissioning as needed and the thresholds may be adjusted automatically based on the selected freeze limits. If the temperature exceeds (is lower than) the first selected threshold, then the heat pump system 100 operates the heat pump system 100 and the auxiliary heat 139 at an increased capacity or increased or full capacity based on demand of 103 in FIG. 1 as depicted at process step 220. Optionally the method 200 continues at process step 225 with determining if the temperature associated with the liquid in the geothermal loop 152 is lower than a second selected threshold. If the temperature is lower than the second selected threshold, then the heat pump system operates the heat pump system 100 and the auxiliary heat 139 at further increased/higher capacity including full capacity independent of the demand of 103 in FIG. 1 as depicted at process step 230. In one embodiment the second selected threshold is established at a temperature of 34° F. Though other temperatures are possible for the second selected threshold as described herein. In an embodiment the auxiliary heat is operated at full capacity independent of the demand. For example, a higher threshold may be employed for water alone in the geothermal loop, while lower thresholds could be employed if the geothermal loop employs various additive antifreeze solutions. For example, with, a 15% propylene glycol solution the first threshold may be lowered to approximately 38° F., while the second threshold might be reduced to 26° F. Likewise, for other antifreeze additives various thresholds may be employed as described.

Continuing with the method 200, as depicted at process step 235, optionally it is determined if the measured temperature associated with the liquid in the geothermal loop increases sufficiently to be above a third selected threshold. If it is determined if the temperature associated with the liquid in the geothermal loop 152 is greater than the third selected threshold, then the heat pump system 100 operates with the auxiliary heat 139 in a reduced capacity as depicted at optional process step 240. Once again, in an embodiment, the first selected threshold is selected for a temperature of the liquid in the geothermal loop 152 at temperature far enough away from the freezing temperature to permit the heat pump system to extract heat from the geothermal loop 152. Steps 235 and 240 optional, and such are shown in FIG. 2 as a dashed.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more features, integers, steps, operations, element components, and/or groups thereof. For the purposes of this disclosure, it is further understood that the terms “inboard” and “outboard” can be used interchangeably, unless context dictates otherwise.

While the present disclosure has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. Rather, the present disclosure can be modified to incorporate any number of variations, alterations, substitutions, combinations, sub-combinations, or equivalent arrangements not heretofore described, but which are commensurate with the scope of the present disclosure. Additionally, while various embodiments of the present disclosure have been described, it is to be understood that aspects of the present disclosure may include only some of the described embodiments.

Claims

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.