GSI Outdoors PNEG-377 - Manual (Page 45)

45
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-
ing valve, turn the T-handle out (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.
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.
Wait until temperature under bin has equalized as
before. If temperature under bin is less than the