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Subtractive Pressuretrol Control
I have a Burnham Low Pressure Steam Boiler Model MST396. The burner has a Subtractive Pressuretrol as seen in Dan's Book on p. 124. The burner technician has set the control for the Differential (left control) at 1. The control for the Main (right control) is set below the marking for 1 and half way to the bottom of the register. I don't understand this setting for 1/2 lb of pressure!