Apparatus controlling a plurality of fuels of different heat contents to a fluid heater burner including valves for selectively connecting the fuels to the burner and pressure responsive fuel flow regulators responding to {TAIL ~ the combined fuel/air pressure} at the fuel burner to provide a given level of output for {HEAD ~ the boiler} 
Apparatus controlling a plurality of fuels of different heat contents to a fluid heater burner including valves for selectively connecting the fuels to the burner and pressure responsive fuel flow regulators responding to { TAIL ~ the combined fuel / air pressure } at the fuel burner to provide a given level of output for { HEAD ~ the boiler }
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