American Dryer Corp. AD-400 - Manual (Page 47)

Once main flame is established, the burner will remain in the hi-fire mode until the drying set point
temperature has been reached. At this point, the dryer computer will cycle the hi/lo butterfly valve to
the lo-fire position. The lo-fire mode will be maintained until the dryer's temperature falls below the
drying set point temperature. The butterfly valve will then be returned to the hi-fire position. The hi-fire
to lo-fire cycling will continue for the remainder of the drying cycle. When 115 volts AC is applied to the
motor of the butterfly valve, it moves to the hi-fire position. Lo-fire is achieved when no voltage is
applied to the butterfly valve motor.
3. Gas Burner Startup
New gas lines are filled with air and must be purged before the burner will light.
1. Close the upp>er manual shut-off valve, but leave the pilot line shut-off valve opjen. Push in the
test/reset button on the cover of the burner controller module (BCM). This will "freeze" the
ignition sequence when the pilot flame ignites. This will allow time to examine the pilot flame,
and measure the flame rod signal to the burner controller module.
Connect a pressure gauge or water tube to the pilot gas pressure tap.
2. Start the dryer. Follow the ignition process by referring to the "Sequence of Op>eration" section
of this manual.
When the pilot flame is ignited, the pilot gas pressure should measure 3.5 inches water column
for natural gas and 15 inches water column for L.P. gas. The pilot flame should be about as
big as a tennis ball.
Insert the positive probe of a DC volt meter into the "flame signal" port on the cover
of the burner controller module. Connect the negative probe to ground. A 3-11 VDC reading
must be obtained. If the reading is less than 3 VDC, then adjust the pilot inlet pressure
regulator so that the pilot gas pressure is at the proper setting. If the voltage reading is still
below 3 VDC, then adjust the internal screw of the pilot gas cock to increase the size of the pilot
flame.
If the voltage reading is still too low, then remove the flame rod and clean it with soap and
water. TTiis should provide a better signal. The pilot flame should heat the flame rod so it is
red hot.
3. Once the pilot flame has been properly set, remove the pressure gauge from the pilot line and
connect a differential pressure gauge between the nuiin gas pressure tap (hi port) and the air
pressure tap (lo port) on the side of the gas burner box. The lines connecting the gauge to these
taps must be long enough to allow the gauge to sit outside of the dryer so that the burner
section access doors can be closed when the dryer runs. Running the dryer with these doors
open will give an incorrect air pressure reading.
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