WATER HEATER WITH INSULATING LAYER

Abstract

A water heater includes: an inner tank having an internal cavity configured to hold water therein; a heating device residing in the internal cavity; an outer lining that surrounds the inner tank, a gap being present between the outer lining and the inner tank; and insulation material located in the gap. The gap is under a vacuum of between about 5 and 200 microns. In this configuration, the water heater can have an R value in excess of 500. With this level of insulative capacity, water stored in the water heater may lose only 2° F. or less over a 24 hour period, thereby substantially outperforming conventional water heaters.

Description

FIELD OF THE INVENTION

The present invention is directed generally to heating devices, and more particularly to water heaters.

BACKGROUND OF THE INVENTION

Typical water heaters that are currently available utilize foam or fiberglass insulation around a tank that heats and stores hot water. Electricity, gas, geothermal or solar energy ordinarily provides the heat source for the water. The insulation medium that surrounds the tank typically has an R value (a well-known measure of thermal resistance) of 7 to 12. These values typically result in a heat loss of 2° F. or more per hour. As a result, as a general rule water heaters need to frequently fire and reheat the stored water to be able to provide water of the desired temperature upon demand. Water heater life is usually 7-13 years—with proper maintenance—and most units typically last less than 10. Heat pump and gas condensing units associated with conventional water heaters also generally require additional maintenance and parts replacement.

Heating water is typically the second largest energy requirement in the home. As such, manufacturers are continually seeking ways to reduce energy input. Many efforts have focused on reducing the electric/gas input requirements. Some manufacturers are pursuing heat pump and gas condensing product innovations to reduce energy needs; however, these approaches can be expensive and are somewhat unproven.

Tank-less water heaters are another alternative. However, tankless water heaters available today tend to be limited in water flow capacity during demand and usually require significant service over time. Units are sized based on the number of “hot outlets” that are needed for a given number of residents of a household. Units for many outlets/people tend to be expensive and, even with the energy tax credits that are currently available, recovering the cost of the unit based on energy savings is rare.

SUMMARY OF THE INVENTION

As a first aspect, embodiments of the present invention are directed to a water heater. The water heater comprises: an inner tank having an internal cavity configured to hold water therein; a heating device residing in the internal cavity; an outer lining that surrounds the inner tank, a gap being present between the outer lining and the inner tank; and insulation material located in the gap. The gap is under a vacuum of between about 5 and 200 microns. In this configuration, the water heater can have an R value in excess of 500. With this level of insulative capacity, water stored in the water heater may lose only 2° F. or less over a 24 hour period, thereby substantially outperforming conventional water heaters.

As a second aspect, embodiments of the present invention are directed to a water heating system, comprising: a heat exchange fluid (HEF) tank; one or more solar panels; a first line fluidly connecting the HEF tank with the solar panels; a water heater, the water heater including a heat exchanger; a second line fluidly connecting the HEF tank with the heat exchanger; a third line fluidly connecting the solar panels with the heat exchanger; and a pump located on one of the first, second or third lines.

As a third aspect, embodiments of the present invention are directed to a water heating system, comprising: a heat exchange fluid (HEF) tank; one or more solar panels; a first line fluidly connecting the HEF tank with the solar panels; a water heater, the water heater including a heat exchanger; a second line fluidly connecting the HEF tank with the heat exchanger, wherein one of the first line and the second line includes a first valve, and wherein the second line includes a second valve; a third line fluidly connecting the solar panels with the heat exchanger, the third line including a third valve; a pump located on one of the first, second or third lines; and a controller operably associated with the first, second and third valves.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a longitudinal section view of a water heater according to embodiments of the present invention.

FIG. 2 is a longitudinal section view of the outer lining of the water heater of FIG. 1 prior to its assembly with the inner tank.

FIG. 3 is a longitudinal section view of the inner tank of the water heater of FIG. 1.

FIG. 4 is a longitudinal section view of the inner tank of FIG. 3 with an outer cap attached thereto.

FIG. 5 is a longitudinal section view of the water heater of FIG. 1 with the inner tank and outer cap of FIG. 4 assembled with the outer lining of FIG. 2.

FIG. 6 is a side view of the water heater of FIG. 1 in an assembled condition.

FIG. 7 is a schematic diagram of an exemplary residential solar heating system employing a water heater of FIG. 1 according to embodiments of the present invention.

FIG. 8 is a schematic diagram of an exemplary commercial solar heating system employing water heaters according to embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The present invention will now be described more fully hereinafter, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. Thicknesses and dimensions of some components may be exaggerated for clarity.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. 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 other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein the expression “and/or” includes any and all combinations of one or more of the associated listed items.

In addition, spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. Thus, the exemplary term “under” can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

Well-known functions or constructions may not be described in detail for brevity and/or clarity.

Referring now to the drawings, a water heater according to embodiments of the present invention, designated broadly at 10, is shown in FIG. 1. The water heater 10 includes an inner tank 12 in which water is stored. The inner tank 12 may be formed of a number of different materials; in this embodiment, the inner tank 12 is formed of stainless steel, preferably type 300 stainless steel, or glass-lined carbon steel

A heat exchanger 14 is located within the inner tank 12 that provides energy to heat water stored within the inner tank 12. The heat exchanger 14 can be of any design or configuration known to those of skill in this art to be suitable for transferring heat to a fluid medium. The water heater 10 also includes a cold water inlet 16 and a hot water exit 18 through which water can flow into and out of the inner tank 12. In this embodiment, a pressure and temperature relief valve and pressure gauge 20 is mounted on the hot water exit 18. A sacrificial anode 22 also extends into the inner tank 12. These components may be of conventional design known to those of skill in this art and need not be described in detail herein.

The water heater 10 also includes an outer lining 24 (see also FIG. 2). The outer lining 24 comprises an outer layer 26 (in this embodiment formed of a thermoplastic such as an extruded polypropylene copolymer or a metal such as stainless or carbon steel) and an inner layer 28 that serves to provide a vacuum-tight environment within the outer lining 24. In some embodiments, the inner layer 28 is formed of thin aluminum; in other embodiments, the inner layer 28 is formed of a thin layer of ceramic microspheres and/or fiberglass wrap.

As can be seen in FIG. 1, the outer lining 24 is formed to be larger than the inner tank 12, such that a gap 30 exists between the inner tank 12 and the outer lining 24. The gap 30, which is typically between 3 and 4 inches in thickness, is filled with a highly insulative material 32. Exemplary highly insulative materials include ceramic microspheres (e.g., glass microspheres available from 3M, Inc., Minneapolis, Minn.), perlite, and a two-piece warp formed of foil and tissue (available under the name “Superinsulation”). Also, in the illustrated embodiment, the gap 30 is subjected to a vacuum of between about 5 and 200 microns, and in other embodiments to a vacuum of between about 5 and 20 microns. A vacuum pump port 25 with a vacuum valve 29 extends into the gap 30 and is configured to be connected to a vacuum pump (not shown). Some embodiments may have no vacuum within the gap 30. As illustrated, the water heater 10 may include supports 27 between the inner layer 28 and the inner tank 12 to maintain the spacing of the gap 30.

In this configuration, the water heater 10 can have an R value in excess of 500. With this level of insulative capacity, water stored in the water heater 10 may lose only 2° F. or less over a 24 hour period, thereby substantially outperforming conventional water heaters. Because the temperature of the stored water is so much more stable than that of conventional water heaters, much less energy is required to maintain the temperature of the water. Also, the absence of moving parts in the water heater 10 can increase its life span, which may be up to 30 years or more.

The energy to operate the heat exchanger 14 to heat the water stored in the inner tank 12 may be provided in any form known to be suitable to those of skill in this art. For example, the energy may be electrical, gas, solar, wind, geothermal, or the like. Solar, wind and geothermal energy may be particularly appealing in some embodiments due to the inexpensive nature of generating the energy. As such, it is contemplated that the heat exchanger 14 may be connected with one or more solar panels or cells, a wind-driven turbine, or a geothermal cell.

Referring now to FIGS. 2-6, a manufacturing and assembly method according to embodiments of the present invention is illustrated. The water heater 10 shown therein has an injection-molded thermoplastic outer layer 26 and a ceramic microsphere inner layer 28 that comprise the outer lining 24. FIG. 2 shows the outer lining 24 after it has been injection molded; in this embodiment, the ceramic microspheres of the inner layer 28 are bonded to the outer layer 26 during the injection molding process. Typically, the outer layer 26 is between about 0.25 and 0.375 inches in thickness, and the inner layer 28 is between about 0.25 and 0.375 inches in thickness. In this embodiment, the outer layer 26 includes annular ribs 26a to improve the strength of the outer layer 26 under vacuum. Also, in this embodiment the outer lining 24 is split into the large, open-ended portion shown in FIG. 2 and a cap that fits over the open end. In other embodiments, the outer layer 28 may comprise a thin metallic foil.

Referring now to FIG. 3, an exemplary configuration of an inner tank 12′ is shown. The inner tank 12′ is similar to the inner tank 12 described above, but includes electrically-energized heating elements 14′ rather than the heat exchanger 14. FIG. 4 shows the attachment of the plastic cap (lined with ceramic microspheres) to the upper end of the inner tank 12. Also, a steel ring 40 is attached to the middle of the inner tank 12; the ring includes support rods 42 that brace the inner tank 12 when it is inserted into the outer lining 24. FIG. 5 shows the inner tank 12 lowered into the outer lining 24 and the cap of the outer lining 24 sealed to the remainder of the outer lining 24. FIG. 6 is a front view of the completed water heater 10.

It will also be understood to those of skill in this art that the heat exchanger 14 may be replaced with another variety of heating device, such as an electrically driven heating element or the like.

Referring now to FIG. 7, an exemplary solar heating system, designated broadly at 100, is illustrated therein. As can be seen in FIG. 7, the system 100 includes a water heater 10 of the variety described above. The system 100 also includes solar panels 102 of conventional construction that receive solar energy and convert it to heat. Those of skill in this art will understand the construction and operation of the solar panels 102, which need not be discussed in detail herein. The system 100 further includes a heat exchange fluid (HEF) tank 152 that houses a heat exchange fluid (e.g., a mixture of ethylene glycol and water). The interconnections between the solar panels 102, the water heater 10 and the HEF tank 152 are discussed below.

A line 104 connects the solar panel 102 with the exit port of the heat exchanger 14 located in the water heater 10. A solenoid valve 106 is located on the line 104, as is a check valve 108.

A line 110 extends between the entry port of the heat exchanger 14 and an exit port of the glycol tank 152. A solenoid valve 118 is located on the line 110, as is a pump 150. A second solenoid valve 136 is located on the line 110 near the HEF tank 152.

A line 111 extends between the solar panels 102 and an entry port of the HEF tank 152. A check valve 138 is located on the line 111 near the HEF tank 152, and a check valve 130 is located on the line 111 near the solar panels 102.

A branch line 140 extends between the lines 102, 111 to create a fluid circuit with the solar panels 102 that includes the check valve 130 and the solenoid valve 106. A solenoid valve 140 is located on the branch line 140.

A branch line 132 extends between the lines 110, 111 to create a bypass of the HEF tank 152. A solenoid valve 128 is located on the branch line 132. In some embodiments, this line is omitted.

A branch line 114 extends between the lines 102, 110 to create a bypass of the water heater 10. A solenoid valve 116 is located on the branch line 114.

An HEF cooling line 120 forms a loop with the line 110, meeting the line 110 on either side of the solenoid valve 118. The HEF cooling line 120 includes a solenoid valve 124 and a check valve 122.

The system 100 also includes three thermocouples 144, 146, 148. The thermocouple 144 is located on the water heater 10 and detects the temperature of the water inside. The thermocouple 146 is located on the HEF tank 152 and monitors the temperature of the heat exchange fluid inside. The thermocouple 148 is located on the line 111 and monitors the temperature of the heat exchange fluid therein.

The system 100 also includes a controller 154. The controller 154 is configured for communication with the solenoid valves 106, 112, 116, 118, 124, 128, 136, 142 and with the thermocouples 144, 146, 148.

In operation, the system 100 begins with the solenoid valves 136, 118, 112 and 106 open and the solenoid valves 128, 124, 116 and 142 closed. This arrangement creates a fluid circuit in which a glycol/water mixture is conveyed by the pump 150 from the solar panels 102 to the HEF tank 152, then to the heat exchanger 14 of the water heater 10, and back to the solar panels 102. The heat exchange fluid can be heated in the solar panels 102 and transported to the HEF tank 152. Heated heat exchange fluid is transported to the heat exchanger 14, where it heats water in the water heater 10. The heat exchange fluid then returns to the solar panels 102 for further heating.

If the thermocouple 144 associated with the water heater 10 detects that the temperature of the water therein is above a threshold temperature (e.g., 125° F.), the controller 154 signals the solenoid valve 112 to close and the solenoid valve 116 to open. This forms a circuit in which the water heater 10 is bypassed, as the water temperature is already adequate for use.

If the thermocouple 146 associated with the HEF tank 152 detects that the temperature of the HEF tank 152 exceeds a threshold temperature (e.g., 175° F.), the controller 154 signals the solenoid valve 136 to close and the solenoid valve 128 to open. This action removes the HEF tank 152 from the circuit described above and results in the cooling of the heat exchange fluid. If temperature measured by the thermocouple 146 drops below a threshold temperature (e.g., 170° F.) and the temperature measured by the thermocouple 148 is above that threshold temperature, the solenoid valve 136 opens and the solenoid valve 128 closes to restore the circuit described above in order to introduce additional heat energy into the HEF tank 152.

If the thermocouple 148 (which measures the temperature of the heat exchange fluid shortly after it exits the solar panels 102) detects a temperature above a threshold temperature (e.g., 175°), and if the temperature at the thermocouple 146 is above its threshold and the temperature at the thermocouple 144 is above its threshold, the controller 154 signals the solenoid valves 112, 142, 118, 136 to close and solenoid valves 106, 124, 116, 128 to open. This action creates a circuit that lacks the HEF tank 152 and the water heater 12 and includes the glycol cooling line 120. The pump 150 pumps the heat exchange fluid through the HEF cooling line 120 until the thermocouple 148 measures a temperature below its threshold temperature.

In the event that the thermocouples 144, 146 are above their threshold temperatures and the thermocouple 148 is below its threshold temperature, the controller 154 signals the pump 150 to cease operation.

In the event that the thermocouple 148 falls below a low threshold temperature (e.g., 120°), the controller 154 signals the solenoid valve 106 to close and solenoid valve 142 to open. The solenoid valve 128 also closes and the solenoid valve 136 opens. This action creates a circuit that lacks the solar panels 102 and utilizes heat exchange fluid from the HEF tank 152. This circuit may be used when the solar panels 102 are generating insufficient energy to heat the heat exchange fluid (e.g., at night or during a cloudy day). This capacity can assist the system in operating adequately in low solar energy inputs periods by utilizing heat energy that is stored in the heat exchange fluid within the HEF tank 152. Those skilled in this art will note that other materials, such as molten salt (sodium acetate trihydrate), may be employed as the heat exchange fluid.

Referring now to FIG. 8, a commercial water heating system, designated at 300, is illustrated therein. The system 300 includes three water heaters 10a, 10b, 10c that are similar to the water heater 10 described above. The system 300 includes solar panels 302 of the type described above. The remainder of the system 300 is described below.

A heat exchange fluid line 304 extends between the solar panels 302 and the tanks 10a, 10b, 10c. A pump 352 is located within the line 304. A check valve 305 is located between the solar panels 302 and the pump 352. Branch lines 306, 308, 310 extend from the line 304 to the entry ports of the heat exchangers 14 within, respectively, the tanks 10a, 10b, 10c. Each of the branch lines 306, 308, 310 includes a respective solenoid valve 312, 314, 316.

A second heat exchange fluid line 318 extends between the tanks 10a, 10b, 10c and the solar panels 302. Three branch lines 320, 322, 324 extend between the line 318 and the exit ports of the heat exchangers 14 of, respectively, the tanks 10a, 10b, 10c. A respective check valve 326, 328, 330 is located on each branch line 320, 322, 324. A solenoid valve 331 is located on the line 318 between its intersection with the branch line 324 and the solar panels 302.

A cold water supply line 346 leads from a cold water source 347 to the tanks 10a, 10b, 10c. Branch lines 348, 350, 354 lead from the line 346 to, respectively, the tanks 10a, 10b, 10c. A respective check valve 356, 358, 360 is located on each branch line 348, 350, 354.

A hot water line 332 leads from the tanks 10a, 10b, 10c to a hot water destination 333. Branch lines 334, 336, 338 extend between the line 332 and respective tanks 10a, 10b, 10c. A respective solenoid valve 340, 342, 344 is located on each branch line 334, 336, 338. A mixing valve 362 connects the cold water supply line 346 with the hot water supply line 332.

A respective thermocouple 364, 366, 368 is mounted on each tank 10a, 10b, 10c to measure the water temperature therein. A thermocouple 370 is located on the line 304 between the check valve 305 and the pump 352.

The system 300 includes a controller 380 that is configured to control the operation of the solenoid valves 312, 314, 316, 331, 340, 342, 344 and the thermocouples 364, 366, 368, 370.

In operation, the system 300 begins with the tanks 10a, 10b, 10c being filled with cold water, and all of the solenoid valves 312, 314, 316, 331, 340, 342, 344 being closed. When the system 300 is activated, solenoid valve 331 is opened, as is the solenoid valve 312. This action creates a circuit for the heat exchange fluid between the solar panels 302 and the tank 10a, wherein the heat exchange fluid is heated via the solar panels 302 and pumped through the circuit by the pump 352. When the thermocouple 364 senses that the water in the tank 10a has reached a certain temperature (e.g., 160° F.), the controller 380 closes the solenoid valve 306 and opens the solenoid valve 308. This action creates a circuit between the solar panels 302 and the tank 10b. When the water in the tank 10b reaches the desired temperature as measured by the thermocouple 366, the controller 380 closes the solenoid valve 308 and opens the solenoid valve 310, thereby creating a circuit between the solar panels 302 and the tank 10c. The tank 10c is then allowed to reach the desired temperature.

If the temperature measured by thermocouple 370 differs by no more than a predetermined magnitude (e.g., 15° F.) from the temperature measured by the thermocouples 364, 366, 368, the controller 380 signals the pump 352 to cease operation.

If the event water is needed at its destination 333, the solenoid valve 340 opens, and water is supplied to the mixing valve 362 from the tank 10a. If the thermocouple 364 senses that the water temperature in the tank 10a is below a predetermined threshold (e.g., 100° F.), the solenoid valve 340 closes and the solenoid valve 342 opens and supplies water to the mixing valve 362. If the thermocouple 366 senses that the water temperature in the tank 10b is below a predetermined threshold, the solenoid valve 342 closes and the solenoid valve 344 opens and supplies water to the mixing valve 362. If the thermocouple 368 senses that the water temperature in the tank 10c is below a predetermined threshold, the solenoid valve 344 closes. Once demand for water is met, water in the tanks 10a, 10b, 10c is heated sequentially in the manner described above.

The foregoing embodiments are illustrative of the present invention, and are not to be construed as limiting thereof. Although exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

1. A water heater, comprising: an inner tank having an internal cavity configured to hold water therein;a heating device residing in the internal cavity;an outer lining that surrounds the inner tank, a gap being present between the outer lining and the inner tank; andinsulation material located in the gap;wherein the gap is under a vacuum of between about 5 and 200 microns.

2. The water heater defined in claim 1, wherein the insulation material comprises ceramic microspheres.

3. The water heater defined in claim 1, wherein the outer lining comprises an inner layer and an outer layer.

4. The water heater defined in claim 3, wherein the inner layer comprises one of a thin metallic foil and a thin layer of ceramic microspheres.

5. The water heater defined in claim 3, wherein outer layer comprises one of a thermoplastic or a metal.

6. The water heater defined in claim 3, wherein the outer layer comprises a thermoplastic and the inner layer comprises a thin layer of microspheres.

7. The water heater defined in claim 6, wherein the outer layer is injection-molded and the inner layer is bonded to the outer layer during injection molding.

8. The water heater defined in claim 1, further comprising supports in the gap to maintain the gap.

9. The water heater defined in claim 1, wherein the outer lining has a two-piece construction.

10. A water heating system, comprising: a heat exchange fluid (HEF) tank;one or more solar panels;a first line fluidly connecting the HEF tank with the solar panels;a water heater, the water heater including a heat exchanger;a second line fluidly connecting the HEF tank with the heat exchanger;a third line fluidly connecting the solar panels with the heat exchanger; anda pump located on one of the first, second or third lines.

11. The water heating system defined in claim 10, wherein the water heater comprises: an inner tank having an internal cavity configured to hold water therein;a heating device residing in the internal cavity;an outer lining that surrounds the inner tank, a gap being present between the outer lining and the inner tank; andinsulation material located in the gap;wherein the gap is under a vacuum of between about 5 and 200 microns.

12. The water heating system defined in claim 10, further comprising a fourth line fluidly connecting the first and second lines to isolate the HEF tank from the solar panels, the pump and the heat exchanger.

13. The water heating system defined in claim 10, further comprising a fifth line fluidly connecting the first and third lines to isolate the solar panels from the HEF tank, the pump and the heat exchanger.

14. The water heating system defined in claim 10, further comprising a sixth line fluidly connected to the second line and the third line to isolate the heat exchanger from the solar panels, the pump and the HEF tank.

15. The water heating system defined in claim 10, further comprising a seventh line fluidly connected to two points on the second line, the seventh line providing a cooling loop for fluid in the second line.

16. A water heating system, comprising: a heat exchange fluid (HEF) tank;one or more solar panels;a first line fluidly connecting the HEF tank with the solar panels;a water heater, the water heater including a heat exchanger;a second line fluidly connecting the HEF tank with the heat exchanger, wherein one of the first line and the second line includes a first valve, and wherein the second line includes a second valve;a third line fluidly connecting the solar panels with the heat exchanger, the third line including a third valve;a pump located on one of the first, second or third lines; anda controller operably associated with the first, second and third valves.

17. The water heating system defined in claim 16, further comprising a fourth line fluidly connecting the first and second lines to isolate the HEF tank from the solar panels, the pump and the heat exchanger, the fourth line including a fourth valve operably associated with the controller.

18. The water heating system defined in claim 17, further comprising a first thermocouple associated with the HEF tank, and wherein the controller is configured to close the first valve and open the fourth valve if the first thermocouple detects a temperature above a predetermined threshold.

19. The water heating system defined in claim 16, further comprising a fifth line fluidly connecting the first and third lines to isolate the solar panels from the HEF tank, the pump and the heat exchanger, the fifth line including a fifth valve operably associated with the controller.

20. The water heating system defined in claim 19, further comprising a second thermocouple associated with the first line, and wherein the controller is configured to close the third valve and open the fifth valve if the second thermocouple detects a temperature below a predetermined threshold.

21. The water heating system defined in claim 16, further comprising a sixth line fluidly connected to the second line and the third line to isolate the heat exchanger from the solar panels, the pump and the HEF tank, the sixth line including a sixth valve operably associated with the controller.

22. The water heating system defined in claim 21, further comprising a third thermocouple associated with the water heater, and wherein the controller is configured to close the second valve and open the sixth valve if the third thermocouple detects a temperature above a predetermined threshold.

23. The water heating system defined in claim 16, further comprising a seventh line fluidly connected to two points on the second line, the seventh line including a seventh valve operably associated with the controller and providing a cooling loop for fluid in the second line.