American Dryer Corp. AD-400 - Manual (Page 43)

d Pilot Gas Supply Line
The pilot gas supply line consists of a manual shut-off valve, pressure regulator, electric solenoid valve,
back-loaded pressure regulator, and an adjustable gas cock.
The gas pressure in this line should be approximately 35 inches water column for natural gas and 15
inches water column for L.P. gas. This will provide a bushy pilot flame, which produces a 3-11 DC volt
signal from the flame rod to the burner controller module.
This flame can be adjusted in two (2) ways.
1. Pilot Inlet Pressure Regulator - Remove the cap and turn the slotted adjustment screw
clockwise for more gas and counterclockwise for less gas.
2. Adjustable Pilot Gas Cock - Remove the cap and turn the slotted adjustment screw clockwise
for less gas and counterclockwise for more gas.
The pilot line contains a back-loaded pressure regulator with an impulse line connected to the gas burner
inlet. This regulator will maintain a constant pilot supply pressure as the pressure in the burner changes
due to an increase in temperature. Do not adjust this regulator
e. Main Gas Supply Line
The main gas supply line consists of a pressure regulator, two (2) motorized shut-off valves, hi/lo gas
pressure switch, manual shut-off valve, electric butterfly valve, manual butterfly valve, and lo-fire check
valve.
The gas pressure at the burner should be 2.2 inches water column above the duct pressure for natural gas
and .9 inches water column for L.P. gas. This pressure is measured by a differential pressure gauge or
water tube. Connect the hi port of the gauge to the main gas pressure tap, and the lo port of the gauge to
‘ the air pressure tap on the side of the burner box. This pressure can be adjusted by the pressure
regulator. Remove the cap of the regulator and turn the slotted adjustment screw clockwise for higher
gas pressure and counterclockwise for lower gas pressure. The gas pressure can also be changed by
adjusting the manual butterfly valve.
The gas burner works on a hi-fire/lo-fire system. Hi-fire is set at 1,600,000 Btuh, while lo-fire is set at
40,000 Btuh. The hi-fire rate is set by the manual butterfly valve while the lo-fire rate is set by the electric
butterfly valve.
• Motorized Gas Valves
The Eclipse series 500"MV" 1-1/2 FPT motorized valves are "on/off" gas flow control valves. The valves
open slowly, and the internal spring return closes the valves within one (1) second of power shutoff.
The valve motors operate on 115 VAC and are electrically "cascaded" so that upper valve will not open
until the lower valve has fully opened. A limit switch inside each motorized valve provides the signal
that the valve is fully opened. TTiese valves will begin to open only when the burner controller module is
receiving a 3-11 DC signal from the flame rod proving that the pilot flame is established.
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