Grain Systems PNEG-816 - Manual (Page 19)

19
Deluxe Vane Axial Heater
LTD HEATER OPERA-
TION
Modulating Valve Operation
Your LTD heater is equipped with a modulating
valve. The following material should be read
thoroughly.
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 read-
ing side top up. The bulb reacts to temperature.
It changes the amount of gas (increase or de-
crease), 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 dry-
ing air. If the bulb is warmer than it was at the
SET POINT, the valve closes further and reduces
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. To set the regulator, run the
heater and turn the modulating valve T-handle
in. This gets full line pressure 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. Wait
until temperature under bin has equalized as before.
If temperature under bin is less than the desired
temperature, continue turning T-handle in, in-
creasing gas flow and waiting for plenum tem-
perature to equalize until the desired tempera-
ture is the stable temperature of the plenum. 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 condi-
tions as long as humidistat or thermostat do not
shut down the heater. A bypass orifice is used
to maintain a small flame when outside tempera-
ture is near or above the set point of the valve.
The bypass insures steady application of heat
at minimum gas flow operation.
6. The modulating valve may require minor adjust-
ment periodically if a certain temperature rise
over ambient (outside) temperature is desired.
7. 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 ambient
(outside) temperature is significantly greater
later in the day (as normal), the gas pressure will
be less. Since less heat is required to maintain
the same temperature in the plenum, the modu-
lating valve will have reduced the amount of
gas used by the heater. This is preferred to cy-
cling the application of heat as is com-
monly done. The grain is not shocked
and cooled quickly and then r e h e a t e d ,
which is a waste of fuel in conven-
tional bin drying systems.