TM 5-3895-374-24-2MAIN GAS VALVEHYDRAMOTORThe gas valve on your heater is equipped with a proof of closure switch. This is an externallymounted micro-switch which is actuated and closes the control circuit when the gas valve hasreturned to the closed position. It prevents the burner from recycling if the gas valve did not fullyclose following the previous burner cycle.The hydramotor and valve assembly are "PUSH when energized" type for ON-OFF operation. Theoperating mechanism is completely immersed in oil, which eliminates usual maintenance andservice. (See Gas Flow Schematic, Section 5.9)OperationWhen the actuator terminals are powered, the relief valve closes and the electric motor-drivenpump applies hydraulic pressure to the spring-loaded piston, pushing the actuator stemdownward. When the actuator stem reaches full travel, the travel limit switch opens the pumpmotor circuit to stop the pump action. The relief valve remains energized and closed, holding thestem downward. When the control circuit is broken, the relief valve opens and the spring-loadedpiston and valve stem return to the up, de-energized, position, closing the valve. Note that whenactuator is held in energized position, the motor may restart intermittently to maintain properpressure against the piston.CAUTION:USE MIL SPEC 5606 OIL FOR REFILLING HYDRAULIC UNIT, AVAILABLEFROM ITT GENERAL CONTROLS, OR USE GEMLINE REFRIGERATION OIL,AVAILABLE FROM MOST REFRIGERATION SERVICE OUTLETS.1.Remove fill plug from top of actuator pump unit.2.Fill unit with oil to within 1/4 to 1/2 inch from bottom of fill plug hole.page 3 - 1160
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