Direct Gas Make-Up Air
51
Troubleshooting
Direct Gas-Fired Heat
Pressure drop across the burner
between 0.625 - 0.675 in. wg for
natural gas (0.8 - 0.9 in.wg for LP gas)?
Yes
No
Adjust fan speed and/or burner baffles to achieve
0.625 - 0.675 in. wg for natural gas (0.8 - 0.9 in.wg for LP gas)
pressure drop.
Air in the gas line?
No
Yes
Purge the gas line.
Pilot gas valve passing gas pressure to
pilot gas pressure test port?
Yes
No
Pilot gas valve (PV) faulty
. Replace pilot gas valve.
Pilot gas pressure set correctly?
Yes
No
Set pilot gas pressure to recommended value.
Is a spark visible or audible during the
trial for ignition?
Yes
No
Spark and flame wires crossed
. Uncross wires and reconnect.
Incorrect spark plug gap.
Set spark plug gap to 0.062 in.
Defective spark plug.
Replace spark plug.
Spark generator faulty.
Replace spark generator.
At this time, the pilot flame should light.
Red flame light on flame
safeguard (FSG) illuminated?
No
Yes
Skip to question that reads,
Yellow main light on flame
safeguard (FSG) illuminated?
Flame rod dirty or corroded?
No
Yes
Clean flame rod
. Remove corrosion with emery cloth.
Replace flame rod.
Electrical continuity from control center
end of flame wire to flame rod boot?
Yes
No
Flame wire broken.
Replace wire.
Connection at flame rod boot failed.
Repair connection.
Flame rod boot corroded
. Replace flame rod boot.
Electrical continuity from flame wire to
ground?
No
Yes
Shield or spare wire touching flame wire in flame rod boot.
Cut
shield or spare wire back to eliminate contact.
Burr from flame rod threads touching flame rod
. Remove burr.
Flame rod or flame rod porcelain
cracked or deteriorated?
No
Yes
Replace flame rod.
120 VAC or more on terminal 'S' on
flame safeguard amplifier?
Yes
No
Check wiring in flame safeguard subbase.
Correct any wiring
issues.
Flame safeguard (FSG) or flame safeguard amplifier faulty.
Replace flame safeguard or flame safeguard amplifier.
1.25 VDC or higher on terminals [+] &
[-] on flame safeguard amplifier?
Yes
No
Pilot pressure too low
. Increase pilot pressure.
Check wiring in flame safeguard subbase
. Correct any wiring
issues.
Flame safeguard (FSG) or flame safeguard amplifier faulty.
Replace flame safeguard or flame safeguard amplifier.
With a flame signal of 1.25 VDC or higher, the red flame light on the flame safeguard should be illuminated.
Yellow main light on flame
safeguard (FSG) illuminated?
Yes
No
Check wiring in flame safeguard subbase
. Correct any wiring
issues.
Flame safeguard (FSG) faulty.
Replace flame safeguard.
115 VAC between terminals 110 and
101?
Yes
No
Check wiring in flame safeguard subbase
. Correct any wiring
issues.
Flame safeguard (FSG) faulty
. Replace flame safeguard.
Gas pressure at outlet of the first
solenoid valve?
Yes
No
Inlet gas pressure too high.
Reduce inlet gas pressure to below the
maximum gas pressure.
Solenoid valve stuck shut
. Tap valve gently to loosen.
Solenoid failed.
Replace solenoid or valve assembly.
Gas pressure at outlet of second
solenoid valve?
Yes
No
Solenoid valve stuck shut.
Tap valve gently to loosen.
Solenoid failed
. Replace solenoid or valve assembly.
Main burner flame lit?
Yes
No
Low fire set too low.
Adjust low fire as described in the burner
startup section.
Everything is working properly, consult factory.
A
B
B