Dungs 226464 FRG 725/6 proportionator/zero governor regulators have an adjustable setpoint spring and nonadjustable counterspring. They are recommended for industrial and commercial heating applications. It is suitable for natural gas, propane, butane, air and other inert gases.Application (Proportionator): Holds a constant gas/air ratio by varying gas flow to a gas burning piece of equipment in proportion to combustion air flow. Adjustable ratio for excess gas or air operation. Application (Zero Governor): Controls fuel by reducing incoming gas pressure to zero or adjustable to slightly above or below atmospheric pressure. Features: Aluminum body; Two upstream and downstream taps; air impulse line on top; Refer to selection guide for technical specifics, flow and pressure drop. Optional low fire bypass for 3/8” - 2” (225256) for 705/6, 707/6, 710/6, 712/6, 715/6, 720/6.Input gas pressure for Proportionator: 2 to 82 in. W.C. (5 to 200 mbar); Zero Governor: 2 to 20 in. W.C. (5 to 50 mbar). Output gas pressure for Proportionator: 4 to 60 in. W.C. (10 to 150 mbar); Zero Governor: -2 to 2 in. W.C. (-5 to 5 mbar) See spring selection. Max operating pressure: 7 PSI (500 mbar).