Fluid Heater

Abstract

A fluid heater ( 100 ) comprising a storage reservoir ( 1 ) for storing heating fluid, a burner ( 5 ) for heating the heating fluid and a first heat exchanger ( 11 ) located outside said storage reservoir ( 1 ). The heater ( 100 ) also comprises a first fluid circuit ( 200 ) connecting the storage reservoir ( 1 ) with the first heat exchanger ( 11 ) for carrying heating fluid from the storage reservoir ( 1 ), through the first heat exchanger ( 11 ) and back to the storage reservoir ( 1 ), and a second fluid circuit ( 300 ) connecting a first inlet ( 19 ) for mains fluid to a first outlet ( 27 ) for heated mains fluid via the first heat exchanger ( 11 ). The first heat exchanger ( 11 ) is adapted to exchange heat between said heating fluid and said mains fluid.

1 . A fluid heater comprising:
 a storage reservoir for storing heating fluid;   a burner for heating the heating fluid;   a first heat exchanger located outside said storage reservoir;   a first fluid circuit connecting the storage reservoir with the first heat exchanger for carrying heating fluid from the storage reservoir, through the first heat exchanger and back to the storage reservoir; and   a second fluid circuit connecting a first inlet for mains fluid to a first outlet for heated mains fluid via the first heat exchanger,   wherein the first heat exchanger is adapted to exchange heat between said heating fluid and said mains fluid.   
     
     
         2 . A fluid heater according to  claim 1 , wherein the first heat exchanger includes a first pipe-in-pipe heat exchanger. 
     
     
         3 . A fluid heater according to  claim 2 , wherein the first pipe-in-pipe heat exchanger includes a first thermally conductive pipe for containing the heating fluid, said first thermally conductive pipe being located within a second thermally conductive pipe for containing the mains fluid. 
     
     
         4 . A fluid heater according to  claim 2 , wherein the first pipe-in-pipe heat exchanger includes a first thermally conductive pipe for containing the mains fluid, said first thermally conductive pipe being located within a second thermally conductive pipe for containing the heating fluid. 
     
     
         5 . A fluid heater according to  claim 3 , wherein the first heat exchanger includes a plurality of the first and second thermally conductive pipes, with each said first thermally conductive pipe being located within a respective said second thermally conductive pipe. 
     
     
         6 . A fluid heater according to  claim 5 , wherein the first thermally conductive pipes are connected in parallel and the second thermally conductive pipes loop backward and forward through the first heat exchanger. 
     
     
         7 . A fluid heater according to  claim 1 , wherein the first heat exchanger is adapted to be heated by combustion products generated by the burner. 
     
     
         8 . A fluid heater according to  claim 7 , wherein the burner is a gas burner and the first heat exchanger is located above the gas burner, such that combustion products from the gas burner rise toward the first heat exchanger. 
     
     
         9 . A fluid heater according to  claim 1 , further comprising a second heat exchanger, downstream of the first heat exchanger with respect to a flow direction of the heating fluid, for exchanging heat between the heating fluid and the mains fluid. 
     
     
         10 . A fluid heater according to  claim 9 , wherein the second heat exchanger is located below the first heat exchanger, such that combustion products passing the second heat exchanger rise toward the first heat exchanger to heat the first heat exchanger. 
     
     
         11 . A fluid heater according to  claim 9 , wherein the second heat exchanger includes a second pipe-in-pipe heat exchanger. 
     
     
         12 . A fluid heater according to  claim 11 , wherein the second pipe-in-pipe heat exchanger includes a third thermally conductive pipe for containing the mains fluid, said third thermally conductive pipe being located within a fourth thermally conductive pipe for containing the heating fluid. 
     
     
         13 . A fluid heater according to  claim 11 , wherein the second pipe-in-pipe heat exchanger includes a third thermally conductive pipe for containing the heating fluid, said third thermally conductive pipe being located within a fourth thermally conductive pipe for containing the mains fluid. 
     
     
         14 . A fluid heater according to  claim 9 , further comprising a third heat exchanger, downstream of the first heat exchanger with respect to a flow direction of the heating fluid, for exchanging heat between the heating fluid and the mains fluid. 
     
     
         15 . A fluid heater according to  claim 14 , wherein said third heat exchanger is downstream of the second heat exchanger with respect to a flow direction of the heating fluid. 
     
     
         16 . A fluid heater according to  claim 14 , wherein the third heat exchanger is located above the second heat exchanger. 
     
     
         17 . A fluid heater according to  claim 14 , wherein the third heat exchanger is located in the storage reservoir. 
     
     
         18 . A fluid heater according to  claim 1 , further comprising a first valve for selectively preventing flow of the heating fluid through the first heat exchanger. 
     
     
         19 . A fluid heater according to  claim 18 , further comprising a second valve for selectively preventing flow of the heating fluid from the storage reservoir. 
     
     
         20 . A fluid heater according to  claim 1 , further comprising an expansion valve between the second fluid circuit and the first fluid circuit to allow mains fluid to pass from the second fluid circuit into the first fluid circuit when pressure within the second fluid circuit increases to a predetermined level. 
     
     
         21 . A fluid heater according to  claim 18 , further comprising a controller adapted to close the first valve, in response to a first flow sensor sensing flow of mains fluid, to thereby prevent heating fluid from flowing through the first heat exchanger. 
     
     
         22 . A fluid heater according to  claim 21 , wherein the controller is adapted to actuate a heating sequence of the burner in response to the first flow sensor sensing flow of mains fluid and a first temperature sensor indicating a heating fluid temperature below a first predetermined value. 
     
     
         23 . A fluid heater according to  claim 22 , wherein the first predetermined value is approximately 82° C. 
     
     
         24 . A fluid heater according to  claim 21 , wherein the controller is adapted to deactivate the burner in response to the first flow sensor sensing flow of mains fluid and a first temperature sensor indicating a heating fluid temperature above a second predetermined value. 
     
     
         25 . A fluid heater according to  claim 24 , wherein the second predetermined temperature is approximately 85° C. 
     
     
         26 . A fluid heater according to  claim 21 , wherein the controller is adapted to open the first valve in response to the first flow sensor sensing a stoppage of mains fluid flow, to thereby allow heating fluid to flow through the first heat exchanger to scavenge residual heat in the first heat exchanger. 
     
     
         27 . A fluid heater according to  claim 21 , wherein the controller is adapted to actuate the burner in response to the first flow sensor sensing a stoppage of mains fluid flow and a second temperature sensor indicating a heating fluid temperature below a third predetermined value. 
     
     
         28 . A fluid heater according to  claim 27 , wherein the third predetermined value is approximately 65° C. 
     
     
         29 . A fluid heater according to  claim 21 , wherein the controller is adapted to deactivate the burner in response to the first flow sensor sensing a stoppage of mains fluid flow and a second temperature sensor indicating a heating fluid temperature above a fourth predetermined value. 
     
     
         30 . A fluid heater according to  claim 29 , wherein the fourth predetermined temperature is approximately 80° C. 
     
     
         31 . A fluid heater comprising:
 a storage reservoir for storing heating fluid;   a burner for heating the heating fluid;   a first heat exchanger;   a first fluid circuit connecting the storage reservoir with the first heat exchanger for carrying heating fluid from the storage reservoir, through the first heat exchanger and back to the storage reservoir; and   a second fluid circuit connecting an inlet for mains fluid to an outlet for heated mains fluid via the first heat exchanger, the second fluid circuit including a portion that passes through an exhaust path of burner heat expelled after heating of the heating fluid,   wherein the first heat exchanger is adapted to exchange heat between said heating fluid and said mains fluid.   
     
     
         32 . A fluid heater according to  claim 31 , wherein the first heat exchanger includes a first pipe-in-pipe heat exchanger. 
     
     
         33 . A fluid heater according to  claim 32 , wherein the first pipe-in-pipe heat exchanger includes a first thermally conductive pipe for containing the heating fluid, said first thermally conductive pipe being located within a second thermally conductive pipe for containing the mains fluid. 
     
     
         34 . A fluid heater according to  claim 32 , wherein the first pipe-in-pipe heat exchanger includes a first thermally conductive pipe for containing the mains fluid, said first thermally conductive pipe being located within a second thermally conductive pipe for containing the heating fluid. 
     
     
         35 . A fluid heater according to  claim 33 , wherein the first heat exchanger includes a plurality of the first and second thermally conductive pipes, with each said first thermally conductive pipe being located within a respective said second thermally conductive pipe. 
     
     
         36 . A fluid heater according to  claim 35 , wherein the first thermally conductive pipes are connected in parallel and the second thermally conductive pipes loop backward and forward through the first heat exchanger. 
     
     
         37 . A fluid heater according to  claim 31 , wherein the first heat exchanger is adapted to be heated by combustion products generated by the burner. 
     
     
         38 . A fluid heater according to  claim 37 , wherein the burner is a gas burner and the first heat exchanger is located above the gas burner, such that combustion products from the gas burner rise toward the first heat exchanger. 
     
     
         39 . A fluid heater according to  claim 31 , further comprising a second heat exchanger, downstream of the first heat exchanger with respect to a flow direction of the heating fluid, for exchanging heat between the heating fluid and the mains fluid 
     
     
         40 . A fluid heater according to  claim 39 , wherein the second heat exchanger is located below the first heat exchanger, such that combustion products passing the second heat exchanger rise toward the first heat exchanger to heat the first heat exchanger. 
     
     
         41 . A fluid heater according to  claim 39 , wherein the second heat exchanger includes a second pipe-in-pipe heat exchanger. 
     
     
         42 . A fluid heater according to  claim 41 , wherein the second pipe-in-pipe heat exchanger includes a third thermally conductive pipe for containing the mains fluid, said third thermally conductive pipe being located within a fourth thermally conductive pipe for containing the heating fluid. 
     
     
         43 . A fluid heater according to  claim 41 , wherein the second pipe-in-pipe heat exchanger includes a third thermally conductive pipe for containing the heating fluid, said third thermally conductive pipe being located within a fourth thermally conductive pipe for containing the mains fluid. 
     
     
         44 . A fluid heater according to  claim 39 , further comprising a third heat exchanger, downstream of the first heat exchanger with respect to a flow direction of the heating fluid, for exchanging heat between the heating fluid and the mains fluid. 
     
     
         45 . A fluid heater according to  claim 44 , wherein said third heat exchanger is downstream of the second heat exchanger with respect to a flow direction of the heating fluid. 
     
     
         46 . A fluid heater according to  claim 44 , wherein the third heat exchanger is located above the second heat exchanger. 
     
     
         47 . A fluid heater according to  claim 44 , wherein the third heat exchanger is located in the storage reservoir. 
     
     
         48 . A fluid heater according to  claim 31 , further comprising a first valve for selectively preventing flow of the heating fluid through the first heat exchanger. 
     
     
         49 . A fluid heater according to  claim 31 , further comprising a second valve for selectively preventing flow of the heating fluid from the storage reservoir. 
     
     
         50 . A fluid heater according to  claim 31 , further comprising an expansion valve between the second fluid circuit and the first fluid circuit to allow mains fluid to pass from the second fluid circuit into the first fluid circuit when pressure within the second fluid circuit increases to a predetermined level. 
     
     
         51 . A fluid heater according to  claim 48 , further comprising a controller adapted to close the first valve, in response to a first flow sensor sensing flow of mains fluid, to thereby prevent heating fluid from flowing through the first heat exchanger. 
     
     
         52 . A fluid heater according to  claim 51 , wherein the controller is adapted to actuate a heating sequence of the burner in response to the first flow sensor sensing flow of mains fluid and a first temperature sensor indicating a heating fluid temperature below a first predetermined value. 
     
     
         53 . A fluid heater according to  claim 52 , wherein the first predetermined value is approximately 82° C. 
     
     
         54 . A fluid heater according to  claim 51 , wherein the controller is adapted to deactivate the burner in response to the first flow sensor sensing flow of mains fluid and a first temperature sensor indicating a heating fluid temperature above a second predetermined value. 
     
     
         55 . A fluid heater according to  claim 54 , wherein the second predetermined temperature is approximately 85° C. 
     
     
         56 . A fluid heater according to  claim 51 , wherein the controller is adapted to open the first valve in response to the first flow sensor sensing a stoppage of mains fluid flow, to thereby allow heating fluid to flow through the first heat exchanger to scavenge residual heat in the first heat exchanger. 
     
     
         57 . A fluid heater according to  claim 51 , wherein the controller is adapted to actuate the burner in response to the first flow sensor sensing a stoppage of mains fluid flow and a second temperature sensor indicating a heating fluid temperature below a third predetermined value. 
     
     
         58 . A fluid heater according to  claim 57 , wherein the third predetermined value is approximately 65° C. 
     
     
         59 . A fluid heater according to  claim 51 , wherein the controller is adapted to deactivate the burner in response to the first flow sensor sensing a stoppage of mains fluid flow and a second temperature sensor indicating a heating fluid temperature above a fourth predetermined value. 
     
     
         60 . A fluid heater according to  claim 59 , wherein the fourth predetermined temperature is approximately 80° C. 
     
     
         61 . A fluid heater according to  claim 31 , wherein the first heat exchanger is located outside the storage reservoir. 
     
     
         62 . A method for heating fluid, said method comprising the steps of:
 providing a supply of heating fluid;   heating the heating fluid;   providing mains fluid;   heating the mains fluid by exchanging heat between said heating fluid and said mains fluid; and   further heating the mains fluid using residual heat from the step of heating the heating fluid.   
     
     
         63 . A method according to  claim 62 , including the further step of reheating the heating fluid if the temperature of the heating fluid falls below a predetermined lower limit. 
     
     
         64 . A method according to  claim 62 , including the further step of stopping the heating step if the temperature of the heating fluid reaches a predetermined upper limit. 
     
     
         65 . A method according to  claim 63 , including the step of changing the lower limit based on whether mains fluid is flowing. 
     
     
         66 . A method according to  claim 64 , including the step of changing the upper limit based on whether mains fluid is flowing. 
     
     
         67 . A method according to  claim 62 , including the additional step of heating fluid in an external hydronic heating circuit by exchanging heat between the heating fluid in the first fluid circuit and fluid in the hydronic heating circuit. 
     
     
         68 . A method according to  claim 67 , including the additional step of stopping the exchange of heat between the heating fluid in the first fluid circuit and fluid in the hydronic heating circuit if a temperature of the heating fluid in the first fluid circuit falls below a predetermined lower limit.