GSI Outdoors PNEG-377 service manual Modulating Valve Operation, Amount of gas used by the heater

Fan and Heater OPERATING PROCEDURE

Modulating Valve Operation

1.The modulating valve regulates gas flow through the heater based on sensing unit in the plenum, and maintains a constant drying air temperature.

2.The sensing bulb of the modulating valve should be mounted through the bin wall with the side reading "top" up. The bulb reacts to tempera- ture. It changes the amount of gas (increase or decrease), burning warmer or cooler depending on the position of the valve SET POINT. If the bulb is cooler than it was at the SET POINT, the bulb senses the cooler temperature and opens the valve further so more heat is applied to the drying air. If the bulb is warmer than it was at the SET POINT, the valve closes further and re- duces the temperature until the air is at the valve

SET POINT.

3.It is important that the pressure regulator be set high enough to allow the modulating valve to deliver enough gas to maintain the plenum tem- perature necessary. The regulator is normally factory set at 15 psi (propane units). To set the regulator, run the heater and turn the modulat ing valve T-handle in. This gets full line pres- sure to the burner. Then adjust regulator to read 15 psi (depending on the plenum temperature needed).

4.Turn the fan and heater on. To set the modulat- ingvalve,turntheT-handleout(counterclockwise)

until loose and wait a few minutes for the ple- num temperature to equalize. When the tempera- ture under the bin has equalized, gradually turn T-handle in (clockwise) about 1/2 turn at a time.

Waituntiltemperatureunderbinhasequalizedas before. Iftemperatureunderbinislessthanthe

desired temperature, continue turning T-handle in, increasing gas flow and waiting for plenum temperature to equalize until the desired tem- perature is the stable temperature of the ple

num. If temperature under bin is the same 10 minutes after you last made any adjustments to the T-handle you can be certain that the temperature under the bin is the SET POINT of the valve. 1 turn of the T-handle equals approximately 7 degrees F of temperature.

5.The valve will now keep the plenum tempera- ture at the set point regardless of ambient

conditions as long as humidistat or thermostat do not shut down the heater. A bypass orifice is used to maintain a small flame when out- side temperature is near or above the set point of the valve. The bypass insures steady appli- cation of heat at minimum gas flow operation. Bypass orifice will only operate correctly if pressure regulator is set correctly.

6.To observe how the modulating valve increases the efficiency of bin drying, check the gas pres- sure of the unit in the morning and compare to the pressure read mid-afternoon. If the ambi- ent (outside) temperature is significantly greater later in the day (as normal), the gas pres sure will be less. Since less heat is required to maintain the same temperature in the plenum, the modulating valve will have reduced the

amount of gas used by the heater.

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