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GSA
Gas-Fired Steam Boilers –
Boiler Manual
19
Part Number 550-110-738/1012
7 Start-up
continued
Verify operation
Check burner flame — Pilot burner
Proper pilot flame (see Figure 19):
1. Blue flame.
2. Inner cone engulfing thermocouple.
3. Thermocouple glowing cherry red.
Improper pilot flame:
1. Overf
ired — Large flame lifting or blowing past thermo
couple.
2. Underfired — Small flame. Inner cone not engulfing
thermocouple.
3. Lack of primary air — Yellow flame tip.
4. Incorrectly heated thermocouple.
Check burner flame — Main burner
Proper main burner flame (see Figure 20):
1. Yellow‑orange streaks may appear (caused by dust).
Improper main burner flame:
1. Overfired — Large flames.
2. Underfired — Small flames.
3. Lack of primary air — Yellow tipping on flames (sooting will
occur).
Figure 19
Typical pilot burner flame
Check vent damper operation
1. Raise room thermostat to call for heat — Vent damper actuator
will slowly open vent damper.
2. When vent damper is fully open — Main gas valve will open
and main burners will ignite.
Vent damper must be fully open before main burn-
ers light. If vent damper does not fully open, flue
products such as carbon monoxide will escape into
house, causing severe personal injury or death.
3. Lower thermostat setting — Main burner flames will go out,
then vent damper will close.
4. Repeat Steps 1 through 3 several times to verify operation.
5. Return thermostat to normal setting.
6. Set thermostat heat anticipator setting indicated on wiring
diagram.
Check venting system operation
With boiler firing, hold a candle or match below lower edge of draft
hood “skirt.” If flame does not blow out, but burns undisturbed,
the vent system is working properly. If flame blows out or flickers
severely, the vent system must be checked for obstructions or
other causes of improper venting.
Figure 20
Typical main burner flame