REGULATORS
Control valve
Air
Air and gas mix in venturi
Mixer
Gas
Atmospheric (0) pressure
A
Built-in limiting orifice
Atmospheric (0) pressure
Drip leg
Air/gas ration regulator
ATMOSPHERIC REGULATOR SUPPLYING A PREMIX BURNER SYSTEM
As air flow through the venturi increases, increased suction causes more gas flow through the limiting orifice valve. This in turn slightly reduces the pressure at "A" which causes the regulator to open and allow more gas to flow and maintain the atmospheric or "zero gauge" outlet pressure. Because a slight amount of force is required to raise the internals and open the regulator, the pressure at "A" may drop off 1 or 2 tenths of an inch w.c. at full flow. This "droop" has only a minor effect on accuracy of control when the regulator is properly sized.
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