Dual fuel boiler with backflow-preventing valve arrangement

Abstract

A dual fuel boiler has fuel delivery apparatus coupled to its burner section through a pressure regulator and operative to deliver to the burner section, from sources thereof, a selectively variable one of (1) a first fuel at a pressure greater than the pressure regulation setting of the pressure regulator, and (2) a second fuel at a pressure less than the pressure regulation setting, the second fuel having a Wobbe index greater that that of the first fuel. The first fuel is flowed to the burner section via a branch supply line in which first and second electromechanical two position, two-way, two position valves are installed in series in opposite normal flow orientations to thereby prevent backflow of the second fuel into the source of the first fuel.

1 . A fuel-fired heating appliance comprising: 
 fuel burner apparatus having an inlet portion;    pressure regulator apparatus having an outlet portion coupled to said inlet portion of said fuel burner apparatus, and a predetermined pressure regulation setting; and    fuel delivery apparatus coupled to said pressure regulator apparatus inlet portion and operative to deliver thereto a selectively variable one of (1) a first fuel, from a source thereof, at a pressure greater than said predetermined pressure regulation setting, and (2) a second fuel at a pressure lower than said predetermined pressure regulation setting, 
 said fuel delivery apparatus including a fuel supply line communicated with said inlet portion of said fuel burner apparatus and through which one of said first and second fuels may be flowed, and first and second electromechanical two position, two-way valves connected in series in said fuel supply line in opposite normal flow orientations,  
 said pressure regulator apparatus regulating the pressure of fuel discharged from its outlet portion only with respect to said first fuel, and  
   said pressure regulator apparatus and said fuel delivery apparatus being coupled in a manner precluding said pressure regulation setting from being affected by which of said first and second fuels is being delivered to said pressure regulator apparatus.    
   
   
       2 . The fuel-fired heating appliance of  claim 1  wherein: 
 said fuel burner apparatus is of a non-aspirating type, and    said fuel-fired heating appliance further comprises a blower operative to supply combustion air to said fuel burner apparatus.    
   
   
       3 . The fuel-fired heating appliance of  claim 1  wherein: 
 said fuel-fired heating appliance is a boiler.    
   
   
       4 . The fuel-fired heating appliance of  claim 1  wherein: 
 said first fuel is natural gas, and    said second fuel is propane.    
   
   
       5 . The fuel-fired heating appliance of  claim 1  wherein: 
 said fuel delivery apparatus further includes a pressure regulator operative to reduce the pressure of the second fuel when it is being flowed to said fuel delivery apparatus.    
   
   
       6 . The fuel-fired heating appliance of  claim 1  wherein: 
 said fuel burner apparatus comprises a plurality of fuel burners, and    said pressure regulator apparatus comprises a plurality of pressure regulators operatively coupled to said plurality of fuel burners.    
   
   
       7 . A fuel-fired heating appliance comprising: 
 a fuel burner having an inlet orifice;    a fuel delivery system for alternately supplying first and second fuels having different wobbe indexes to said inlet orifice at different pressures related to said different Wobbe indexes in a predetermined manner such that the firing rate of said fuel burner remains substantially the same, without changing said inlet orifice, regardless of which one of said first and second fuels is being supplied to said fuel burner, said fuel delivery system including: 
 a fuel supply line communicated with said inlet orifice and through which one of said first and second fuels may be flowed,  
 first and second electromechanical two position, two-way valves connected in series in said fuel supply line in opposite normal flow orientations,  
 a first pressure regulator through which both of said first and second fuels must flow to reach said fuel burner, and  
 a second pressure regulator through which only the higher Wobbe index fuel must flow to reach said fuel burner.  
   
   
   
       8 . The fuel-fired heating appliance of  claim 7  wherein: 
 said fuel-fired heating appliance is a fuel-fired boiler.    
   
   
       9 . The fuel-fired heating appliance of  claim 7  wherein: 
 said fuel burner is a non-aspirating type burner, and    said fuel-fired heating appliance further comprises a blower operative to supply combustion air to said fuel burner.    
   
   
       10 . The fuel-fired heating appliance of  claim 7  wherein: 
 the pressure regulation setting of said first pressure regulator is higher than the pressure regulation setting of said second pressure regulator.    
   
   
       11 . A fuel-fired heating appliance comprising: 
 non-aspirating type fuel burner apparatus having an orificed fuel inlet portion;    blower apparatus for supplying combustion air to said fuel burner apparatus;    a main fuel supply line structure coupled to said orificed fuel inlet portion;    first pressure regulator apparatus connected in said main fuel line structure and having an inlet portion and a first pressure regulation setting;    a first branch fuel supply line structure, coupled to said inlet portion of said first pressure regulator apparatus for receiving a pressurized first fuel;    a second branch fuel supply line structure, coupled to said inlet portion of said first pressure regulator apparatus, for receiving a pressurized second fuel having a wobbe index higher than that of said first fuel;    valve apparatus operable to permit flow of only a selectively variable one of said first and second fuels to said inlet portion of said first pressure regulator apparatus and thus to said orificed fuel inlet portion of said fuel burner apparatus, said valve apparatus including first and second electromechanical valves connected in series in said first branch fuel supply line structure in opposite normal flow orientations; and    second pressure regulator apparatus connected in said second branch fuel supply line structure and having a second pressure regulation setting, 
 said first and second pressure regulation settings being related to one another in a predetermined manner such that, without altering said orificed fuel inlet portion of said burner apparatus, the firing rate of said burner apparatus will remain essentially constant regardless of which of said first and second fuels is being supplied thereto.  
   
   
   
       12 . The fuel-fired heating appliance of  claim 11  wherein: 
 said fuel-fired heating appliance is a dual fuel boiler.    
   
   
       13 . The fuel-fired heating apparatus of  claim 11  wherein: 
 said burner apparatus comprises a plurality of non-aspirating type fuel burners each having an orificed inlet.    
   
   
       14 . The fuel-fired heating appliance of  claim 11  wherein: 
 said first pressure regulation apparatus comprises a plurality of pressure regulator devices.    
   
   
       15 . The fuel-fired heating appliance of  claim 11  wherein: 
 said first pressure regulation setting is greater than said second pressure regulation setting.    
   
   
       16 . A fuel-fired heating appliance comprising: 
 fuel burner apparatus having an inlet portion; and    fuel delivery apparatus operative to deliver to said fuel burner apparatus a selectively variable one of a first fuel from a source thereof, and a second fuel from a source thereof, 
 said fuel delivery apparatus including a main fuel supply line connected to said inlet portion of said fuel burner apparatus, a first fuel supply branch line connected to said main fuel supply line and connectable to said first source, first valve apparatus connected in said first fuel supply branch line and being openable and closable to selectively permit and preclude flow of said first fuel therethrough, said first valve apparatus including first and second electromechanical two position, two-way valves connected in series, and in opposite normal flow orientations, in said first fuel supply branch line, a second fuel supply branch line connected to said main fuel supply line and connectable to said second source, and second valve apparatus connected in said second fuel supply branch line and being openable and closable to selectively permit and preclude flow of said second fuel therethrough.  
   
   
   
       17 . The fuel-fired heating appliance of  claim 16  wherein: 
 said fuel-fired heating appliance is a dual fuel boiler.    
   
   
       18 . The fuel-fired heating appliance of  claim 16  wherein: 
 said first fuel is natural gas, and said second fuel is propane.