Apparatus and method for converting an electric water heater to use gas

• US 5,203,500 A
• Filed: 05/31/1991
• Issued: 04/20/1993
• Est. Priority Date: 09/19/1989
• Status: Expired due to Fees

• Current Assignee: Gas Fired Products Incorporated
• Original Assignee: Gas Fired Products Incorporated
• Inventors: Horne, Frank L. Sr.
• Primary Examiner(s): Bennett, Henry A.
• Application Number:
  US07/708,750
• Time in Patent Office: 690 Days
• Field of Search: 237/8 R, 237/56, 237/19, 236/20 R, 126/362, 126/101
• US Class Current: 237/19
• CPC Class Codes: F24D 17/00 Domestic hot-water supply systems
• CPC Class Codes: F24H 1/186 using fluid fuel

Abstract

An apparatus and method for providing a hot water supply for a building such as a mobile home, house, or business. A hot water storage tank is positioned within the building. A gas-fueled burner is positioned outside the building adjacent a heat exchanger which is connected in fluid communication with the indoor water storage tank. A pump circulates water from the tank through the heat exchanger and back into the tank responsive to a thermostat in the tank. The heat exchanger includes a thermostat for sensing the temperature of water therein to activate the pump and circulate relatively warm water from the tank through the heat exchanger to prevent freezing of water within the heat exchanger, such as during winter months when the ambient temperature falls below freezing. The gas heater may be used to convert a conventional electric water heater to operate from gas which is combusted outside of the building.

Claims

1. An apparatus for providing a hot water supply for a building, said apparatus compirsing:

a hot water storage tank positioned within the bulding;

a first thermostat positioend in siad hot water storage tank;

a housing mounted outside of teh building;

a gas-fueled burner positioned within siad housing and including means for controlling gas flow thereto;

a heat exchanger positioned within siad housing adjacent said burner, siad heta exchanger having an inlet and an outlet connected in fluid communication with siad hot water storage tnak;

a pump connected in fluid communication with said heat exchanger for circulating ater from siad hot water storage tank through siad heat exchanger and back into siad storage tank;

heater control means operatively conencted to siad first thermostat, siad pump and siad gas flow control measn for activating siad pump and siad burner so that water flows through and is heated in siad heat exchanger when the temperature of the water in siad hot water storage tank falls below a first predetermined temperature; and

a second thermostat positioend within siadh ousing, said second thermostat operatively connected to siad pump so as to activate same when the temperature of water within said heat exchanger falls below a second predetermined temperature to thereby circulate relatively warm water from siad hot water storage tank through siad heat exchanger to thereby prevent freezing of water therein.

2. The apparatus according to claim 1 further comprising a third thermostat positioned within said housing, and wherein said third thermostat is operatively connected to said burner control means for shutting off the flow of gas to said burner when the temperature of water in said heat exchanger exceeds a third predetermined temperature to thereby protect said heat exchanger from damage, such as when the water flowing therethrough is overheated and converted to steam.

3. The apparatus according to claim 1 wherein said second predetermined temperature is no more than about 10°

F. above freezing.

4. The apparatus according to claim 1 further comprising a flow detector positioned in fluid communication with said heat exchanger, and wherein said flow detector is operatively connected to said control means for proving water flow through said heat exchanger prior to activating said burner to thereby prevent damage to said heat exchanger caused by operation of said burner without a sufficient water flow rate through said heat exchanger to cool same.

5. The apparatus according to claim 1 further comprising a standing pilot adjacent said burner for igniting said burner and for providing heat to said heat exchanger to prevent freezing of water therein when the ambient temperature falls below freezing.

6. The apparatus according to claim 1 wherein said pump provides a relatively high flow of water of about 3 to 5 gallons per minute, and wherein said burner and said heat exchanger provide a temperature boost of no less than about 20°

F. to water flowing through said heat exchanger so that a nearly continuous supply of hot water is provided during normal consumption.

7. The apparatus of claim 1 wherein said heat exchanger comprises tubing having a relatively small fluid capacity of no more than a small fraction of the total capacity of said hot water storage tank.

8. The apparatus according to claim 1 wherein said storage tank includes at least one fitting adapted for retaining an electric heating element therein, and wherein said outlet of said heat exchanger is connected in fluid communication with said hot water storage tank through said fitting.

9. The apparatus according to claim 1 further comprising thermal insulation positioned adjacent the interior surface of said housing to reduce heat loss to the ambient air surrounding said housing to thereby increase operating efficiency and reduce the heat required to prevent freezing of water in said heat exchanger when the ambient temperature falls below freezing.

10. An apparatus for providing a hot water supply for a building, said apparatus comprsing:

an indoor hot water storage tank positoiend within the building;

a thermostat positoend in said hot water storage tank;

a housing mounted outside of the building, siad housing incuding an exhaust opening and an air intake opening formed therin;

a gas-fueled burner positioned within siad housing and includnig means for controlling gas flow thereto;

a heat exchanger positioned within siad housing, said heat exchanger having an inlet and an outlet beign connected in fluid commucnation with siad water storage tank, said heat exchanger comrising;

a chamber having an upper opening and a lower opening, siad upper opening communicating with said exchaust opening of siad housing, and said lower opening being positioned ajdacnet siad burner;

a preheater comrising tubing formed in a spiral arrangement adjacent a lowr portion of siad camber for absorbing radiant heat from siad burner; and

a primary heat exchanger postioend above said preheater and cmoprising a series of parallel spaced-apart heat transfer fins and a serpentine arrangement of tubing passing therethrough, siad serpentine tubing of siad parimary heat exchangr bineg in fulid communication with siad preheater tubing;

a pump conected in fluid commucnation with said heat exchangr for ciraulting water rom siad hot water storage tnak through siad heat excanger and back into siad storage tank; and

heater control mnas opratively connected to said thermostat, said pump and siad gas flow control means for actvating siad pump and said burner so that water flows through and is heated in siad heat exchanger when the temperature of the water in siad hot water storage tank falls below a predetermined temperature.

11. The apparatus accoring to claim 10 wherein the surfaces of siad heat transfer fins and said serpentine tubing of siad primary heat exchanger include a black coating thereon to increase absorption of heat from said burner.

12. The apparatus according to claim 10 further comprising a second thermostat positioned within said housing, said second thermostat operatively connected to said pump so as to activate same when the temperature of water within said heat exchanger falls below a temperature of no more than about 10°

F. above freezing to thereby circulate relatively warm water from said hot water storage tank through said heat exchanger to prevent freezing of water therein.

13. The apparatus according to claim 12 further comprising a third thermostat positioned within said housing, and wherein said third thermostat is operatively connected to said burner control means for shutting off the flow of gas to said burner when the temperature of water in said heat exchanger exceeds a third predetermined temperature to thereby protect said heat exchanger from damage, such as when the water flowing therethrough is overheated and converted to steam.

14. The apparatus according to claim 10 further comprising a flow detector positioned in fluid communication with said heat exchanger, and wherein said flow detector is operatively connected to said control means for proving water flow through said heat exchanger prior to activating said burner to thereby prevent damage to said heat exchanger caused by operation of said burner without a sufficient water flow rate through said heat exchanger to cool same.

15. The apparatus according to claim 10 further comprising a standing pilot adjacent said burner for igniting said burner and for providing heat to said heat exchanger to prevent freezing of water therein.

16. The apparatus according to claim 10 wherein said pump provides a relatively high flow of water of about 3 to 5 gallons per minute, and wherein said burner and said heat exchanger provide a temperature boost of no less than about 20°

F. to water flowing through said heat exchanger so that a nearly continuous supply of hot water is provided during normal consumption.

17. The apparatus of claim 10 wherein said preheater tubing and said primary heat exchanger tubing having a combined relatively small fluid capacity of no more than a small fraction of the total capacity of said hot water storage tank.

18. The apparatus according to claim 10 wherein said hot water storage tank includes at least one fitting adapted for retaining an electric heating element therein, and wherein said outlet of said heat exchanger is connected in fluid communication with said storage tank through said fitting

19. The apparatus according to claim 10 further comprising thermal insulation positioned adjacent the interior surface of said housing to reduce heat loss to the ambient air surrounding said housing thereby increasing operating efficiency and reducing the heat required to prevent freezing of water in said heat exchanger when the ambient temperature falls below freezing.

20. An apparatus for providing a hot water supply for a building, said apparatus comprsing:

a generally cylindrical hot water storage tank positioned within the building, said tank having an upper fitting of the type typically used for receiving an electrical heating element therein;

a return tube posiionted within siad hot water storage tank and connectd at siad upper fitting thereo, said return tue being substantially L-shaped to direct water flowing into said tank to mix with the relatively hot water in the upper regions of siad hot water stoage tank;

a thermostat positioned in siad hot water storage tank;

a housing mounted outside of teh building;

a gas-fueled burner positioned within siad housing and including means for controlling gas flow thereto;

a heat exchanger positioned within siad ousing and including means for controlling gas flow thereto;

a heat exchanger positioned adjacent siad burner and positoiend within siad ousng, siad heat exchanger having an inlet in fluid communication with loer regions of siad hot water storage tank so as to permit drawing off of rleatively cool water therefrom, said heat exchanger having an outlet in fulid communication with the upper regions of siad tank through siad return tube;

a pump in fluid communication with siad heat exchagner for circulating water from said hot water storage tank through siad heat exchanger and back into said storage tank; and

heater control mnas opratively connected to said thermostat, said pump and siad gas flow control means for actvating siad pump and said burner so that water flows through and is heated in siad heat exchanger when the temperature of the water in siad hot water storage tank falls below a predetermined temperature.

21. The apparatus according to claim 20 wherein siad generally L-shaped return tube includes a rotatable coupling mounted on an end thereof, and wherein said rotatable coupling is secured to said fitting of said storage tank.

22. The apparatus according to claim 21 wherein said water storage tank has an upright generally cylindrical shape, and wherein said return tube has an angle of about 75°

so that an end of said return tube opposite said coupler end remains in a generally upright orientation within said storage tank by contact with the inner wall of the cylindrical storage tank.

23. The apparatus according to claim 20 further comprising a second thermostat positioned within said housing, said second thermostat operatively connected to said pump so as to activate same when the temperature of water within said heat exchanger falls below a temperature of no more than about 10°

F. above freezing to thereby circulate relatively warm water from said water storage tank through said heat exchanger to prevent freezing of water therein.

24. The apparatus according to claim 23 further comprising a third thermostat positioned within said housing, and wherein said third thermostat is operatively connected to said burner control means for shutting off the flow of gas to said burner when the temperature of water in said heat exchanger exceeds a third predetermined temperature to thereby protect said heat exchanger from damage, such as when the water flowing therethrough is overheated and converted to steam.

25. The apparatus according to claim 20 further comprising a flow detector positioned in fluid communication with said heat exchanger, and wherein said flow detector is operatively connected to said control means for proving water flow through said heat exchanger prior to activating said burner to thereby prevent damage to said heat exchanger caused by operation of said burner without a sufficient water flow rate through said heat exchanger to cool same.

26. The apparatus according to claim 20 further comprising a standing pilot adjacent said burner for igniting said burner and for providing heat to said heat exchanger to prevent freezing of water therein.

27. The apparatus according to claim 20 wherein said pump provides a relatively high flow of water of about 3 to 5 gallons per minute, and wherein said burner and said heat exchanger provide a temperature boost of no less than about 20°

F. to water flowing through said heat exchanger so that a nearly continuous supply of hot water is provided during normal consumption.

28. The apparatus of claim 20 wherein said heat exchanger comprises tubing having a relatively small fluid capacity of no more than a small fraction of the total capacity of said hot water storage tank.

29. The apparatus according to claim 20 further comprising thermal insulation positioned adjacent the interior surface of said housing to reduce heat loss to the ambient air surrounding said housing thereby increasing operating efficiency and reducing the heat required to prevent freezing of water in said heat exchanger when the ambient temperature falls below freezing.

30. A method of converting an electric water heater located inside a building to operate from gas combusted outdoors, the indoor electric water heater including a hot water storage tank with an electric heating element therein and a water temperature responsive thermostat coupled thereto, said method comprising the steps of:

disabling the electrical heating element of the indoor water heater;

positioning a gas-fueled burner and associated heat exchanger outside the building;

connecting the heat exchanger in fluid communication with the indoor hot water storage tank;

connecting a pump in fluid communication between the indoor hot water storage tank and the outdoor heat exchanger; and

providing a control for operation of the pump and gas burner when the indoor tank thermostat senses the temperature of the water in the indoor hot water storage tank falling below a predetermined temperature as when heated water is drawn off causing cold water to enter the storage tank.

31. The method of claim 30 further including the step of proving water flow through the heat exchanger before activating the gas burner to thereby prevent damage to the heat exchanger caused by operation of the burner without a sufficient water flow rate through the heat exchanger to cool same.

32. The method of claim 30 further including the steps of sensing the temperature of water in the heat exchanger and de-activating the gas burner when the sensed temperature exceeds a predetermined temperature to thereby protect the heat exchanger from damage, such as when the water flowing therethrough is overheated and converted to steam.

33. The method of claim 30 wherein the indoor hot water storage tank has a fitting for receipt therein of the electrical heating element, wherein the step of disabling the heating element includes the step of removing the heating element from the heating element fitting;

and wherein the step of connecting the heat exchanger in fluid communication with the indoor hot water storage tank includes the step of positioning a return tube, connected to the outlet of the heat exchanger, in the heating element fitting.

34. The method of claim 30 wherein the indoor hot water storage tank includes a drain valve adjacent the lower regions thereof, and wherein the step of connecting the heat exchanger in fluid communication with the indoor hot water storage tank includes the step of connecting the inlet of the heat exchanger in fluid communication with the indoor hot water storage tank adjacent the drain valve.

35. A method of converting an electric water heater located inside a building to operate from gas combusted outdoors, the indoor electric water heater including a hot water storage tank with an electric heating element therein and a water temperature responsive thermostat coupled thereto, said method comprising the steps of:

disabling the electrical heating element of the indoor water heater;

positioning a gas-fueled burner and associated heat exchanger outside the building;

connecting the heat exchanger in fluid communication with the indoor hot water storage tank;

connecting a pump in fluid communication between the indoor water storage tank and the outdoor heat exchanger;

providing a control for operation of the pump and gas burner when the indoor tank thermostat senses the temperature of the water in the indoor hot water storage tank falling below a predetermined temperature as when heated water is drawn off causing cold water to enter the storage tank; and

adding heat to the heat exchanger when the gas burner is not operating so that water in the heat exchanger is prevented from freezing and damaging the heat exchanger, such as during winter when the ambient temperature drops below freezing and while the water temperature in the indoor water storage tank is sufficiently high so as not to require heating.

36. The method of claim 35 wherein the step of adding heat to the outdoor heat exchanger includes the steps of sensing the temperature of water in the heat exchanger, and operating the pump to circulate relatively warm water from the indoor hot water storage tank through the heat exchanger responsive to the sensed temperature of the water in the heat exchanger falling below a predetermined temperature.

37. The method of claim 35 wherein the step of adding heat to the outdoor heat exchanger includes the step of continuously operating a gas pilot adjacent the outdoor heat exchanger.

38. The method of claim 35 further including the step of proving water flow through the heat exchanger before activating the gas burner to thereby prevent damage to the heat exchanger caused by operation of the burner without a sufficient water flow rate through the heat exchanger to cool same.

39. The method of claim 35 further including the steps of sensing the temperature of the water in the heat exchanger and de-activating the gas burner when the sensed temperature exceeds a predetermined temperature to thereby protect the heat exchanger from damage, such as when the water flowing therethrough is overheated and converted to steam.

40. The method of claim 35 wherein the indoor hot water storage tank has a fitting for receipt therein of the electrical heating element, wherein the step of disabling the heating element includes the step of removing the heating element from the heating element fitting;

and wherein the step of connecting the heat exchanger in fluid communication with the indoor hot water storage tank includes the step of positioning a return tube, connected to the outlet of the heat exchanger, in the heating element fitting.

41. The method of claim 35 wherein the indoor hot water storage tank includes a drain valve adjacent the lower regions thereof, and wherein the step of connecting the heat exchanger in fluid communication with the indoor hot water storage tank includes the step of connecting the inlet of the heat exchanger in fluid communication with the indoor hot water storage tank adjacent the drain valve.

42. An apparatus for provdiing a hot water supply and space heating for abuilding, siad apparatus comprising:

a hot water storage tank positioned within the bulding;

a first thermostat positioend in siad hot water storage tank;

a housing mounted outside of teh building;

a gas-fueled burner positioned within siad housing and including means for controlling gas flow thereto;

a heat exchanger positioned within siad housing adjacent said burner, siad heta exchanger having an inlet and an outlet connected in fluid communication with siad hot water storage tnak;

a pump connected in fluid communication with said heat exchanger for circulating ater from siad hot water storage tank through siad heat exchanger and back into siad storage tank;

heater control means operatively conencted to siad first thermostat, siad pump and siad gas flow control measn for activating siad pump and siad burner so that water flows through and is heated in siad heat exchanger when the temperature of the water in siad hot water storage tank falls below a first predetermined temperature;

a heat exchanger positioned within the building; and

measn connected in fluid communiation with siad heat exchanger within the building for circulating water from said hot water stroage tank therethrough and back into siad stroage tank for thereby supplying heat for space heating of the buliding.

43. An apparatus to claim 42 wherein siad means connected in fluid communication with siad heat exchanger within the building for circulating water from said hot water storage tank therethrough comprises a second pump for circulating water from said hot water storage tank through said heat exchanger within the building and back into said storage tnak.

44. An apparatus according to claim 42 further comprising a second thermostat positiond within siad housing, said second thermostat operatively conected to siad pump so as to activate same when the temperature of water within said heat exchanger falls below a second predetermined temperature to thereby circulate relatively warm water from siad hot water stoage tank through siad heat exchanger to thereby prevent feezing of water therin.

45. An apparatus for providing a hot water supply and space heating for a buiding, siad apparatus comprisign:

a hot water storage tank positioned within the bulding;

a first thermostat positioend in siad hot water storage tank;

a housing mounted outside of teh building;

a gas-fueled burner positioned within siad housing and including means for controlling gas flow thereto;

a heat exchanger positioned within siad housing adjacent said burner, siad heta exchanger having an inlet and an outlet connected in fluid communication with siad hot water storage tnak;

a pump connected in fluid communication with said heat exchanger for circulating ater from siad hot water storage tank through siad heat exchanger and back into siad storage tank;

heater control means operatively conencted to siad first thermostat, siad pump and siad gas flow control measn for activating siad pump and siad burner so that water flows through and is heated in siad heat exchanger when the temperature of the water in siad hot water storage tank falls below a first predetermined temperature; and

a second thermostat positioend within siadh ousing, said second thermostat operatively connected to siad pump so as to activate same when the temperature of water within said heat exchanger falls below a second predetermined temperature to thereby circulate relatively warm water from siad hot water storage tank through siad heat exchanger to thereby prevent freezing of water therein;

a heat exchanger positioned within the building; and

measn iclduing a secodn pump connected in fluid comunication with siad heat exchanger within the building for circulatign water from siad hot water storage tank therethrough and back into siad storage tank for thereby supplying heat for space heating of the building.