Model G3B Gas burner — Instruction manual
MNG3B Gas 041015
20
7. Troubleshooting
(continued)
Problem
Possible
cause
Corrective action
WARNING
These procedures must only be performed by a qualified service
technician. Use care when performing tests on electrically or
mechanically live parts. Disconnect power to burner/appliance and close
main manual gas valve when removing components for service. Failure
to comply could result in severe personal injury, death or substantial
property damage.
Burner pre-
purges for 34
seconds but
does not light
(continued)
Bad primary
control
Check for 24 V on valve lead on control during TFI.
Check for 120 V on HSI lead on control during pre-purge.
Replace primary control if either above tests show negative.
Burner lights but
primary control
locks out after
TFI
Incorrect air
setting
For initial light-off, set air throttle according to desired input.
Wrong orifice
size
Check orifice drill size.
Manifold
pressure
Adjust regulator to 3.5 W.C. for natural gas or propane.
Inadequate gas
supply
Line pressure requirements are: 5.0 W.C. for both natural and propane
fuels.
Line pressure in excess of 14.0 W.C. could damage combination gas
valve.
Watch line pressure gauge during TFI. If pressure drops below minimum
required when gas valve is energized look for partially closed gas cocks
in line, other appliances using the same supply or improperly adjusted
intermediate regulators.
If other appliances are on the same supply line and piping will not
sustain adequate pressure for all units on that piping, then it is
undersized. Check with gas utility.
Insufficient flame
signal
Check flame signal. Minimum signal 0.8 DC microamps.
Improper draft
Improperly adjusted air throttle setting for the fuel input.
Over-fire draft is normally -0.01 W.C. Refer to boiler/furnace
manufacturer’s recommendations for specially packaged units.
Polarity
Check 120 V at L1 on terminal strip.