Apparatus for using cast-off heat to warm water from household water heater

Abstract

A retrofit heat transfer unit, including: a housing for the retrofit unit, including inlet and outlet ports for water and refrigerant; a water pump, in fluid communication with the water inlet port, the water pump adapted to pump water from a water source; a heat exchanger, in fluid communication with the water pump, the water outlet port, the refrigerant inlet port and the refrigerant outlet port; and a thermostat, configured to measure a temperature of the pumped water and activate the water pump when the water is below a predefined low temperature and cease to pump when water is above a predefined high temperature. The retrofit unit is also adapted to receive heated refrigerant fluid from an air conditioner and direct the refrigerant through the heat exchanger and direct the pumped water into the heat exchanger so that the refrigerant heats the water and the water cools the refrigerant.

Description

FIELD AND BACKGROUND OF THE INVENTION

[0001] The present invention relates to a heat transfer apparatus and, more particularly, to an apparatus for transferring heat from an air conditioner unit to water from a water heater.

[0002] A legacy air conditioner uses refrigerant to cool down a space. The refrigerant (e.g. Freon) cools to very low temperatures which is useful in cooling an indoor space. A fan blows air over Evaporator coils (coils which contain cool refrigerant) to cool the room. Another characteristic of the refrigerant used in air conditioners is that it absorbs heat from the air in the room and returns cooled air. The absorbed heat must be released though, and this is the job of the Condenser. Condenser coils are usually located outdoors and have a fan which blows air over the coils (which contain very hot refrigerant, often between 70.degree. C. and 80.degree. C.). The fan air cools the coils and refrigerant so that the refrigerant can be reused to cool the indoor space. In some systems water is used to cool the hot coils instead of fan-blown air.

[0003] Various attempts have been made to utilize the heat generated by the air conditioning system to heat water. Specifically, a number of patents pertain to the use of the heat to warm pool water. U.S. patent application Ser. No. 12/706,883 teaches an air conditioner and pool heater dual system, functioning as a combination air conditioner and water heater having a heat exchanger that includes a refrigerant-to-water heat exchanger, a gas compressor, and at least one evaporator coil. The dual system is capable of heating a pool and refrigerating a house simultaneously using only one compressor. The '833 application fails to disclose a domestic water heater-air conditioner arrangement. A pool heater already includes a pump (for filtering the water) and air conditioning unit (for warming the water), therefore it is logical to expel the cooled air into an enclosed space. A water heater, on the other hand, does not have an existing pump or heating system that has a byproduct which creates cool air. It would therefore be novel to provide a retrofit heat transfer apparatus disposed between an air conditioner and a water heater.

[0004] U.S. Pat. No. 5,560,216 also teaches a combination air conditioner and pool heater. All of the aforementioned deficiencies apply equally here.

[0005] U.S. Pat. No. 4,194,368 teach a combination split system air conditioner and compression cycle domestic hot water heating apparatus including a conventional split system air conditioner combined with a compression cycle or heat pump system for supplying heat to a domestic water heater. The '368 system is a ready made system where both the air conditioner and heating tank have been specially designed. The system does not teach a retrofit system which can be added to existing air conditioning and water heating systems.

[0006] It would be highly advantageous to have a system that utilizes the generated/cast-off heat of an air conditioner to warm water, especially in domestic water-heater systems. It would be most advantageous to provide a retrofit unit that can be simply installed in existing setups which have standard air conditioning and water heating systems, without remodeling either the air conditioner or the water heater. Such an apparatus would be especially useful in high-rise buildings which (for both logistical and esthetic reasons, enforced by local building ordinances) cannot take advantage of solar heating systems and therefore have to both cool the living areas and heat water during the hot seasons.

SUMMARY OF THE INVENTION

[0007] The innovative retrofit heat transfer system of the immediate innovation uses heat produced by an air conditioner compressor to heat the water in a (household) water heater. When refrigerant gas is compressed back into a liquid the line holding the liquid gets very hot (75.degree. C.-85.degree. C.). This heat must be released for the liquid to cool. The refrigerant runs through a coaxial coil heat-exchanger or a plate heat-exchanger in order to cool the refrigerant liquid, which then continues to travel through the condensation coils for continued working. When the air conditioner is active then refrigerant liquid flows through the heat exchanger while cool water is pumped from the water heater--by a water pump--through the heat exchanger, thereby bringing the cool water into contact with the hot refrigerant fluid line. The hot fluid line can have an average temperature of 80.degree. C. The pump action draws cool or cold water from the water heater tank and runs the water through the heat exchanger where the refrigerant is flowing at a temperature of about 80.degree. C., thereby warming the water in the tank after a few cycles through the heat exchanger. At the same time, the refrigerant liquid is cooled by the water from the water tank, removing the need for activating the cooling fan. Therefore innovative unit lowers the cost of running the air conditioner (the cooling fan only runs when the water in the heating tank is too warm to cool the refrigerant fluid) as well as lowering the cost of heating water (the water only needs to be heated for a very short period before becoming hot enough for domestic use). The retrofit unit causes the air conditioner to heat water--at no additional cost of energy--while at the same time cooling the house at a potentially lower cost than normal.

[0008] According to the present invention there is provided a retrofit heat transfer unit, including: (a) a housing for the retrofit unit, including: a water inlet port, a water outlet port, a refrigerant inlet port and a refrigerant outlet port; (b) a water pump, in fluid communication with the water inlet port, the water pump adapted to pump water from a water source; (c) a heat exchanger, in fluid communication with the water pump, the water outlet port, the refrigerant inlet port and the refrigerant outlet port; and (d) a thermostat, configured to measure a temperature of the pumped water, pumped from the water source, such that the water pump is configured to pump water from the water source when the pumped water is below a predefined low temperature and cease to pump the water when the pumped water is above a predefined high temperature, and where the retrofit unit is adapted to receive heated refrigerant fluid from an air conditioner at the refrigerant inlet port and direct the received heated refrigerant fluid through the heat exchanger and further adapted to direct the pumped water into the heat exchanger such that heat from the heated refrigerant fluid is transferred to the water, pumped into the heat exchanger, cooling the heated refrigerant fluid and heating the water, the heated water exiting the housing via the water outlet port.

[0009] According to further features in preferred embodiments of the invention described below the heat exchanger is a co-axial coil heat exchanger or a plate heat exchanger.

[0010] According to still further features in the described preferred embodiments the source is a domestic water heater.

[0011] According to still further features the air conditioner has a cooling function and a heating function for electively cooling and heating an indoor space.

[0012] According to still further features the retrofit unit is configured to receive the heated refrigerant via the refrigerant inlet port from the air conditioner when the air conditioner is in a cooling state or heating state.

[0013] According to still further features a differential between the predefined low temperature and the predefined high temperature is in a range between about 5.degree. C. and 20.degree. C.

[0014] According to still further features the water source is a water supply line from an outdoor water provider and wherein the unit further includes: (e) a valve configured to admit water from the supply line when heated water is being drawn from a water heater to a domestic water distribution system, wherein the water heater is operationally coupled to the retrofit unit via the water inlet port and the water outlet port.

[0015] According to still further features the unit further includes a switch for electively activating and deactivating the thermostat.

[0016] According to still further features the unit further includes (e) a pressostat, configured to deactivate an outdoor cooling fan of the air conditioner when pressure in outdoor coils of the air conditioner is below a predefined compression pressure. Further including a means for circumventing the pressostat.

[0017] According to the present invention there is provided a method of increasing the combined efficiency of an air conditioner and a water heater tank, including the steps of: (a) interposing a retrofit heat exchange unit between an outdoor unit of the air conditioner and the water heater tank; (b) cutting a refrigerant line between a compressor and a 3-way valve of the air conditioner; (c) coupling the refrigerant line from the compressor to a refrigerant inlet port located on a housing of the retrofit unit; (d) coupling the refrigerant line the 3-way valve to a refrigerant outlet port located on the housing; (e) coupling the water heater tank to a water inlet port located on the housing, such that a water pump, disposed inside the housing and coupled to the water inlet port, when activated, is configured to draw water from the water heater tank; and

[0018] (f) coupling the water heater tank to a water outlet port located on the housing, such that heated water, when exiting a heat exchanger disposed in the housing and operationally coupled to the water outlet port, exits the water outlet port and enters the water heating tank, so that refrigerant from the air conditioner heats the water from the water heater tank, in the heat exchanger.

[0019] According to still further features the method further includes the step of (g) connecting a pressostat, disposed in the housing, to the air conditioner, for disconnecting a cooling fan of the outdoor unit when pressure in coils of the outdoor unit falls below a predetermined compression pressure.

[0020] According to still further features the method further includes the step of: (h) installing in a control panel, operationally associated with the housing or the retrofit unit, a circumvention mechanism for circumventing the pressostat.

[0021] According to still further features the method further includes the step of: (g) installing in a control panel operationally associated with the housing, a switch, for electively activating and deactivating the water pump.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Various embodiments are herein described, by way of example only, with reference to the accompanying drawings, wherein:

[0023] FIG. 1 is a typical vapor compression refrigeration system known in the art;

[0024] FIG. 2 is a schematic diagram of the invention within a general setup, with the air conditioner in a cooling state;

[0025] FIG. 3 is a schematic diagram of the invention within a general setup, with the air conditioner in a heating state;

[0026] FIG. 4 is a schematic diagram of a second embodiment of the invention, with the air conditioner in a heating state;

[0027] FIG. 5 is a schematic illustration of a prior art water heating system and an air conditioner prior to installation of the retrofit unit of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The principles and operation of a retrofit heat transfer system according to the present invention may be better understood with reference to the drawings and the accompanying description.

[0029] Referring now to the drawings, FIG. 1 is a typical vapor compression refrigeration system known in the art. The vapor-compression uses a circulating liquid refrigerant as the medium which absorbs and removes heat from the space to be cooled and subsequently rejects that heat elsewhere. FIG. 1 depicts a typical, single-stage vapor-compression system. All such systems have the following four components: a compressor 12, a condenser 14, a Thermal expansion valve 16, and an evaporator 18. Circulating refrigerant enters compressor 12 in the thermodynamic state known as a saturated vapor (i.e. gaseous state) and is compressed to a higher pressure, resulting in a higher temperature as well. The hot, compressed vapor is then in the thermodynamic state known as a superheated vapor and it is at a temperature and pressure at which it can be condensed with typically available cooling water or cooling air. That hot vapor is routed through a condenser where it is cooled and condensed into a liquid by flowing through a coil or tubes with cool water or cool air flowing across the coil or tubes. This is where the circulating refrigerant rejects heat from the system and the rejected heat is carried away by either the water or the air (whichever may be the case).

[0030] The condensed liquid refrigerant, in the thermodynamic state known as a saturated liquid, is next routed through an expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in the adiabatic flash evaporation of a part of the liquid refrigerant. The auto-refrigeration effect of the adiabatic flash evaporation lowers the temperature of the liquid and vapor refrigerant mixture to where it is colder than the temperature of the enclosed space to be refrigerated.

[0031] The cold mixture is then routed through the coil or tubes in the evaporator. A fan circulates the warm air in the enclosed space across the coil or tubes carrying the cold refrigerant liquid and vapor mixture. That warm air evaporates the liquid part of the cold refrigerant mixture. At the same time, the circulating air is cooled and thus lowers the temperature of the enclosed space to the desired temperature. The evaporator is where the circulating refrigerant absorbs and removes heat which is subsequently rejected in the condenser and transferred elsewhere by the water or air used in the condenser.

[0032] To complete the refrigeration cycle, the refrigerant vapor from the evaporator is again a saturated vapor and is routed back into the compressor 12.

[0033] FIG. 2 illustrates a schematic diagram of the invention within a general setup, where the air conditioner is in a cooling state. Unit 100 is the inventive retrofit heat transfer unit of the immediate invention. An air conditioner 150 is coupled to unit 100 in a manner that will be further detailed below. A water heating system 170 is connected to the household plumbing system in a standard fashion and to unit 100 in a manner that will be described in further detail below.

[0034] Air conditioner 150 includes a compressor 151, a two-way expansion valve 154, an outdoor unit including coils 152 and fan 155 and an indoor unit including coils 153 and fan 157. Air conditioners which have an additional heating feature also include a three-way valve 105 (sometimes called a four-way valve when including the inlet port).

[0035] Water heater system 170 includes a water heater tank 181, an intake pipe 172, a cold outlet pipe 174, a hot intake pipe 176 and a hot outlet pipe 178. A thermometer 180 provides a temperature read for cold outlet pipe 174 and a thermostat 179 activates unit 100 and designates the desired temperature of the water. A supply line faucet/valve 177 control the supply of water from an outdoor water source to the heating tank. Hot outlet pipe 178 is coupled to water distribution system 182 from where the hot water is distributed throughout the living area.

[0036] Heat transfer unit 100 includes a heat exchanger 108 and a water pump 106 disposed within housing 101 of the unit. Housing 101 further includes inlet and outlet ports and connecting lines/pipes for facilitating an efficient retrofit installation of unit 100. Refrigerant inlet port 120 is adapted to receive a connection refrigerant line (hot) 103 from compressor 151. Inside housing 101 coupling refrigerant line 104 connects inlet port 120 to heat exchanger 108. A refrigerant outlet line 107 runs from heat exchanger 108 to an outlet port 122 on housing 101. A refrigerant line 109 running from outlet port 122 enters 3-way valve 105 and from there to either the indoor or outdoor coils depending on which state the air conditioner is in (heating or cooling). Housing 101 further includes a water inlet port 124 adapter to receive water from a water source (in the depicted embodiment in FIG. 2 the water source is a domestic water heating tank). A water line 175 runs from port 122 to water pump 106 and from pump 106 to heat exchanger 108. A water outlet port 126 is disposed in housing 101 and coupled to heat exchanger 108. Water outlet port 126 is adapted to be connected to a water pipe 176 which carries heated water to given destination (in the depicted embodiment in FIG. 2 the destination is a domestic water heating tank).

[0037] When air conditioner 150 is in a cooling state, cold refrigerant gas (saturated vapor) travels (direction of travel is indicated by the arrows above the various different gas and liquid lines/coils) through indoor coils 153 whereupon indoor fan 157 blows ambient air over the coils and out of the evaporator unit (usually situated in some form of living space such as a room, office, hall, etc.). In general, the gas absorbs the heat in the ambient air so that cooled air is expelled, cooling (and dehumidifying) the space. The gas continues to travel through the gas line and enters 3-way valve 105 (which is part of air conditioning unit 150 although not drawn as such), whereupon the gas is directed to compressor 151. At the compressor, the gas is compressed to a higher pressure, resulting in a higher temperature as well. The hot, compressed vapor is then in the thermodynamic state known as a superheated vapor and it is at a temperature and pressure at which it can be condensed with typically available cooling water or cooling air, thereby releasing the absorbed heat. The superheated gas/vapor runs along a hot line 103/104 between compressor 151 and heat exchanger 108. At heat exchanger 108, the hot vapor is cooled and condensed into a liquid by flowing through (in one preferred embodiment) the coaxial coil of the heat exchanger with cool water flowing across the internal coil such that heat is transferred from the heated line to the water which is circulated back into water heating tank 181 via hot inlet pipe 176. (The coaxial coil heat exchanger will be discussed in further detail below.) Pump 106 pumps cold or cool water from water heater tank 181--via cold outlet line 174/175--into heat exchanger 108. Heat exchanger 108 acts as a Condenser when infused with cold water. The condensed cooled (or at least cooler) liquid refrigerant then travels into 3-way valve 105 and from there into outdoor coils 152. If the liquid has been sufficiently cooled by heat exchanger 108 then outdoor fan 155 is not activated.

[0038] In one preferred embodiment, a pressostat 160 is coupled to the outdoor coils 152 and fan 155. Pressostat 160 is configured to detect whether the pressure in the coils in below a predetermined level or not. If the pressure is below the predetermined level, then the refrigerant is sufficiently cool and fan 155 is not needed. Otherwise, if the pressure is too high (i.e. the refrigerant is still too hot), then fan 155 continues to blow air over coils 152 to cool the refrigerant (see below for further details).

[0039] Cooled liquid continues to flow from coils 152 to expansion valve 154 where the refrigerant liquid is partially converted back into a cold gas (by undergoing an abrupt reduction in pressure), starting the cycle over.

[0040] If the water coming out of heating tank 181 rises above a predefined temperature, then thermostat 179 deactivates water pump 106 so that no new cool water is pumped through heat exchanger 108. In such a case, the hot gas is not cooled by the heat exchanger and outdoor fan 155 must be activated to cool outdoor coils 152 (which act as the Condenser) in the normal manner. In some embodiments, a pressure switch (e.g. such as a pressostat pressure switch discussed above) determines whether the outdoor fan 155 must be activated or not. In general, the differential between the predefined low temperature at which the pump is activated and the predefined temperature at which the pump ceases is in a range between about 5.degree. C. and 20.degree. C.

[0041] Another possible configuration is shown in FIG. 3. FIG. 3 illustrates a schematic diagram of the invention within a general setup, with the air conditioner in a heating state. In the heating state, 3-way valve 105 reverses the direction in which the refrigerant flows. When heating, the air conditioner/heater uses a refrigerant as an intermediate fluid to absorb heat where it vaporizes (outside), in the evaporator, and then to release heat where the refrigerant condenses (inside), in the condenser. The refrigerant flows through insulated pipes between the evaporator and the condenser, allowing for efficient thermal energy transfer at relatively long distances.

[0042] In heating mode, outdoor coil 152 is an evaporator, while indoor coil 153 is a condenser. The refrigerant flowing from the evaporator (outdoor coil) carries the thermal energy from outside air (or ground) indoors. After traversing coils 152 the refrigerant enters 3-way valve 105 and is directed towards compressor 151. The temperature of the fluid is augmented by compressing the fluid at compressor 151. (The direction of the refrigerant is depicted by the directional arrows.) The super heated vapor then travels via hot line 104 to heat exchanger 108. Cool water flowing through heat exchanger 108 (pumped from water heater tank 181 by water pump 106) cools the fluid down somewhat while heating the water in a heat exchange. The somewhat heated fluid then travels once again to 3-way valve/heat pump 105 and is routed towards indoor coils 153 which transfers thermal energy (including energy from the compression) to the indoor air by fan 157. The refrigerant then travels to two-way expansion valve 154 where the fluid undergoes an abrupt reduction in pressure, cooling the fluid (now a mixture of liquid, and gas). The cycle then repeats itself as the fluid runs through [evaporator] coil 152.

[0043] In some embodiments, a heating element may be added to further heat the ambient air which is blown into the space (such as in a case when indoor coils 152 are not hot enough to heat the indoor space).

[0044] Yet another configuration is shown in FIG. 4. FIG. 4 illustrates a schematic diagram of a second embodiment of the invention, with the air conditioner in a heating state. In the depicted embodiment, a connecting pipe 184 and valve 186 are the only components different from the first embodiment of the invention as depicted in FIG. 2. Connecting pipe 184 forms a bridge between intake pipe 172 and cold outlet pipe 174. Valve 186 has an open state in which supply water runs from intake pipe 172 through connecting pipe 184 into cold outlet pipe 174. Valve 186 has a second state in which the valve is closed, preventing water from running into cold outlet pipe 174.

[0045] In the immediate configuration, in a case where hot water is being utilized during the heating process, cold intake water is diverted from going directly into heating tank 181 (otherwise the cold intake water would cool the water in the tank) and goes, rather, directly into heat exchanger 108. Here, the cold intake water from the supply line serves to better cool the refrigerant running through the heat exchanger and cools the water in the heating tank to a lesser degree because the water enters the tank already slightly warmed from the heat exchanger. Overall, less energy is expended in cooling the refrigerant (fan 155 is activated less) and heating the water in the heating tank (as the hot water in the tank will not cool as fast as normally occurs when cold intake water flows directly into the tank). The aforementioned configuration is equally effective (if not more so) when air conditioner 150 is in a cooling state.

[0046] When water pump 106 is active then valve 186 is opened and when the water pump is deactivated then the valve is closed. Valve 186 may be a solenoid valve.

[0047] Heat exchanger 108 may be a coaxial coil heat exchanger (as hinted at earlier). A coaxial heat exchanger, as most basically explained, can include a length of tubing having inner lumen disposed with the tubing. In the invention, refrigerant flows through the inner lumen while cool water flow through the area between the external tubing and the inner lumen. Heat from the inner lumen warms the water while cooling the refrigerant. A counter-flow heat exchanger is envisioned as being the best mode of practice for the current invention, but the scope of the invention is in no way limited to either coaxial heat exchangers in particular or counter-flow heat exchangers in general.

[0048] Method of Installation

[0049] The method of installation of retrofit unit 100 of the immediate invention will be better understood with reference to FIG. 5 and at least FIG. 3. FIG. 5 is a prior art schematic illustration of a water heating system and an air conditioner prior to installation of the retrofit unit of the invention. Reference is made to both FIGS. 3 and 5, at least.

[0050] Step 1--Position housing 101 of retrofit unit 100 including the heat exchanger 108 and water pump 106 between the water heater tank 181 and the condenser unit of the air conditioner. These two units (tank and condenser) are often proximally located outside the housing unit (on the roof, attached to an outside wall etc.).

[0051] Step 2--Vacuum out refrigerant using a gas recycling machine.

[0052] Step 3--Cut refrigerant line 103 between compressor 151 and 3-way valve 105. Connect an outlet line 103 from compressor 151 to refrigerant inlet port 120 (which is connected to a refrigerant entry on heat exchanger 108) and connect an intake line 109 from refrigerant outlet port 122 to 3-way valve 105.

[0053] Step 4--Replace refrigerant.

[0054] Step 5--Empty water heater tank.

[0055] Step 6--Connect cold outlet pipe 174 from water tank 181 to the water inlet port 124 (which is connected to water pump 106). If an outlet pipe already exists (e.g. connecting to a solar panel) then attach a tee connector (T-connector) with one pipe leading to the existing solar panel (or other arrangement) and the second pipe to water inlet port 124.

[0056] Pipe 175 runs from water pump 106 to the water entryway of heat exchanger 108.

[0057] Step 7--Connect a (warm) water intake pipe 176 from water outlet port 126 back into water tank 181.

[0058] Step 8--Refill water tank.

[0059] In some embodiments, the unit 100 includes a pressostat 160 which is disposed in housing 101 and connected to the condensing unit.

[0060] Step 9--Connect pressostat 160 to line 152 and to cooling fan 155 of the outdoor unit.

[0061] The pressostat functions to disconnect the cooling fan 155 when pressure in the coils is below a predetermined working/compression pressure. The precise working pressure depends primarily on the type of refrigerant used. For example, Freon 22 has a working pressure of approximately 250 psi. On the other hand newer Freon 410 has a working pressure of between approximately 450 and 500 psi. The aforementioned examples are merely exemplary and in no way intended to be limiting. In any case, when the pressure is below the predefined level, then the refrigerant is cool enough and need not be cooled further by cooling fan 155. Therefore, pressostat 160 disconnects the fan, which further saves energy. When using the innovative unit 100 to warm water in cold weather when the heating function of the air conditioner is being used it is necessary to disconnect the pressostat as the external unit now functions as an Evaporator. A circumvention arrangement can be installed to circumvent pressostat 160, where the circumvention unit can be activated manually with a switch or automatically when the air conditioning unit is turned to heating.

[0062] When heating, the indoor fan 157 is only activated once the coils are hot enough. When unit 100 is activated (i.e. water pump is active) coils 153 will take longer to heat up as the heat is first transferred to the water in the heat exchange. Only once the water in water tank 181 is sufficiently hot, and the pump 106 is deactivated, will the pressure be able to build and the coils get hot enough to heat the indoor space. At this time indoor fan 157 will activate to blow hot air into the indoor space. It is therefore generally advisable to activate the air conditioner/heater 150 a sufficient amount of time before heating is required within the indoor space.

[0063] For example, in winter a family wishes to have hot water available for bathing/showering in the evening (e.g. 6:30 pm) and at the same time intends to start heating the house. The air conditioner can be activated at about 6 pm giving the unit about 30 minutes to heat the water in the water tank (this amount of time is purely arbitrary as the actual time will depend and many factor including water temperature, strength of air conditioning/heating unit, size of water take, volume and power of water pump and more). Once the water in water tank 181 has reached a sufficient heat (e.g. 45.degree. C.--which is generally sufficient for bathing, washing dishes or running a washing machine) as preset on thermostat 179, water pump 106 is deactivated and the refrigerant runs into indoor coils 153 without being cooled in heat exchanger 108. A sensor (not shown) connected to fan 157 senses that the heat in the coils is sufficient and activates indoor fan 157 to blow hot air into the indoor space (the heat sensor function is preexisting in heating units and not unique to the present innovation). Should the family desire to have the heater work immediately, a switch 112 on a control box 110 of unit 100 allows for the manual disconnection of water pump 106 even if the water in water tank 181 has not reached the desired temperature.

[0064] In each of the abovementioned embodiments, the heating unit 100 comes to augment the function of the heating element in heating tank 181 so that at any time the heating element can be activated in place of, or in collaboration with, heating unit 100.

[0065] For ease of use, control panel 110 can include the aforementioned special switches and function buttons including but not limited to:

[0066] a switch 114 for circumventing pressostat 160 during the winter months;

[0067] a switch 112 for manually deactivating water pump 106;

[0068] controlling logic and function buttons 116, for setting a desired temperature for thermostat 179 and deferential between the high temperature above which point water pump 106 is deactivated and low temperature below which the water pump is activated;

[0069] a display 118, for showing temperature as measured by thermometer 180 (heat of water in water tank 181) which can be very useful for knowing what the current temperature in water tank 181 is and whether it is necessary to activate heating unit 100 and/or the heating element of the water tank.

[0070] While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. Therefore, the claimed invention as recited in the claims that follow is not limited to the embodiments described herein.

Claims

1. A retrofit heat transfer unit, comprising: (a) a housing for the retrofit unit, including: a water inlet port, a water outlet port, a refrigerant inlet port and a refrigerant outlet port; (b) a water pump, in fluid communication with said water inlet port, said water pump adapted to pump water from a water source; (c) a heat exchanger, in fluid communication with said water pump, said water outlet port, said refrigerant inlet port and said refrigerant outlet port; and (d) a thermostat, configured to measure a temperature of said pumped water, pumped from said water source, such that said water pump is configured to pump water from said water source when said pumped water is below a predefined low temperature and cease to pump said water when said pumped water is above a predefined high temperature, and wherein the retrofit unit is adapted to receive heated refrigerant fluid from an air conditioner at said refrigerant inlet port and direct said received heated refrigerant fluid through said heat exchanger and further adapted to direct said pumped water into said heat exchanger such that heat from said heated refrigerant fluid is transferred to said water, pumped into said heat exchanger, cooling said heated refrigerant fluid and heating said water, said heated water exiting said housing via said water outlet port.

2. The heat transfer unit of claim 1, wherein said heat exchanger is a co-axial coil heat exchanger.

3. The heat transfer unit of claim 1, wherein said heat exchanger is a plate heat exchanger.

4. The heat transfer unit of claim 1, wherein said water source is a domestic water heater.

5. The heat transfer unit of claim 1, wherein said air conditioner has a cooling function and a heating function for electively cooling and heating an indoor space.

6. The heat transfer unit of claim 5, wherein the retrofit unit is configured to receive said heated refrigerant via said refrigerant inlet port from said air conditioner when said air conditioner is in a cooling state.

7. The heat transfer unit of claim 5, wherein the retrofit unit is configured to receive said heated refrigerant via said refrigerant inlet port from said air conditioner when said air conditioner is in a heating state.

8. The heat transfer unit of claim 1, wherein a differential between said predefined low temperature and said predefined high temperature is in a range between about 5.degree. C. and 20.degree. C.

9. The heat transfer unit of claim 1, wherein said water source is a water supply line from an outdoor water provider and wherein the unit further comprises: (e) a valve configured to admit water from said supply line when heated water is being drawn from a water heater to a domestic water distribution system, wherein said water heater is operationally coupled to the retrofit unit via said water inlet port and said water outlet port.

10. The heat transfer unit of claim 1, further comprising a switch for electively activating and deactivating said thermostat.

11. The heat transfer unit of claim 1, further comprising: (e) a pressostat, configured to deactivate an outdoor cooling fan of said air conditioner when pressure in outdoor coils of said air conditioner is below a predefined compression pressure.

12. The heat transfer unit of claim 11, further comprising a means for circumventing said pressostat.

13. A method of increasing the combined efficiency of an air conditioner and a water heater tank, comprising the steps of: (a) interposing a retrofit heat exchange unit between an outdoor unit of the air conditioner and the water heater tank; (b) cutting a refrigerant line between a compressor and a 3-way valve of the air conditioner; (c) coupling said refrigerant line from said compressor to a refrigerant inlet port located on a housing of said retrofit unit; (d) coupling said refrigerant line said 3-way valve to a refrigerant outlet port located on said housing; (e) coupling the water heater tank to a water inlet port located on said housing, such that a water pump, disposed inside said housing and coupled to said water inlet port, when activated, is configured to draw water from the water heater tank; and (f) coupling the water heater tank to a water outlet port located on said housing, such that heated water, when exiting a heat exchanger disposed in said housing and operationally coupled to said water outlet port, exits said water outlet port and enters the water heating tank, so that refrigerant from the air conditioner heats said water from said water heater tank, in said heat exchanger.

14. The method of claim 13, further comprising the step of: (g) connecting a pressostat, disposed in said housing, to the air conditioner, for disconnecting a cooling fan of said outdoor unit when pressure in coils of said outdoor unit falls below a predetermined compression pressure.

15. The method of claim 14, further comprising the step of: (h) installing in a control panel, operationally associated with said housing of said retrofit unit, a circumvention mechanism for circumventing said pressostat.

16. The method of claim 13, further comprising the step of: (g) installing in a control panel operationally associated with said housing, a switch, for electively activating and deactivating said water pump.