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MODU-FIRE® FORCED DRAFT
Gas-Fired Boiler Maintenance
5.6
TROUBLESHOOTING
WARNING
If any “Manual Reset” limit device trips,
DO NOT
reset without
determining and correcting the cause.
(Manual Reset Limits include: Flame safeguard,
high or low gas pressure, high temperature limit,
stack temperature.)
Loss of Power
In the event of loss of power, the entire boiler system
is de-energized, closing all automatic valves and
halting all boiler operations. When power is restored
the sequence of operation will resume at Step 5, pro-
vided that all the limits are satisfied.
Loss of Water Flow
When there is insufficient water flow to close the
flow switch, the "Water Flow" indicator is illumi-
nated, and burner operation is interrupted. When
water flow is re-established, the sequence returns to
Step 2, provided that the other limits are satisfied.
Gas Pressure
When the "Gas Press" indicator is illuminated, there
has been either insufficient gas pressure or the gas
pressure to the manifold is too high for safe and
proper operation of the boiler. The power to termi-
nal 6 on the combustion control will be interrupted,
shutting down the burner.
If a gas-supply shutoff valve is closed for any rea-
son, a low gas condition will result.
When gas pressure is restored, the "Gas Press" indi-
cator will remain on and the boiler will remain
locked out until the gas pressure switch is manually
reset.
In the event of a high gas manifold pressure condi-
tion, the “Gas Press” indicator will illuminate indi-
cating a potential air gas ratio control failure. This
must be corrected by qualified service personnel be-
fore restarting the boiler.
Once the switch is reset, the sequence returns to Step
3, provided that the other limits are satisfied.
High Water Temperature
When the boiler water has exceeded both the operat-
ing and high-limit temperature, power to the pro-
grammer is interrupted. When the water temperature
falls below the high-limit temperature, the boiler will
remain locked out until the switch is manually reset.
Once the switch is reset, the sequence returns to Step
4 to await heat demand provided that the other limits
are satisfied.
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