SG Series Boilers – Installation and Service Manual
42
TROUBLESHOOTING Section 7
Problem Possible Cause Solution
• No power. • Check power switches and wiring.
• No gas supply to boiler. • Check gas source and pressure.
• Gas supply pipes are not purged of air. • Purge gas line.
• No heat demand. • Check if thermostat setting is above room
temperature and aquastat setting is above
boiler water temperature.
• Flame roll-out or blocked vent safety switch
is not reset.
• Push reset and diagnose cause.
• Flow switch or low water cut off. • Check pump capacity & flow direction.
Check for correct water levels and air locks.
• Gas valve failure (closed position). • Check gas valve and replace if necessary.
• Thermocouple failure. • Check thermocouple and replace if
necessary.
• Faulty wiring. • Check wiring of aquastats, zone valves, and
thermostats for loose or broken wires and
repair.
• Faulty controller, aquastat, thermostat, or
zone valve.
• Check and replace if necessary.
Boiler will not fire.
• Pilot not lit. • See "Pilot flame will not light on electronic
ignition".)
• Poor flow in boiler or circulator failure. • Check pump for proper capacity & flow
direction. Replace if necessary.
• Thermostat, heat anticipator, or aquastat
set too low.
• Check and adjust.
• Boiler oversized or insufficient radiation. • Check and adjust if necessary.
Boiler goes on and off at
frequent intervals.
• Wrong type of thermostat or controller. • Check and replace if necessary.
• Gas valve failure (open position). • Check gas valve, replace if necessary.
• Faulty wiring. • Check wiring of aquastats, zone valves, and
thermostats for short circuits or incorrect
wiring.
Boiler fires continuously.
• Faulty controller, aquastat, thermostat, or
zone valve.
• Check and replace if necessary.
• Boiler is overheated and safety high limit
aquastat fails to cut out.
• Check aquastats and adjust or replace if
necessary.
• Improper wiring. • Check and correct.
• Foreign matter in heat exchanger. • Flush heat exchanger if necessary.
• Poor circulation. • Check pump for correct flow.
Rumbling and moaning
sound in boiler.
• Air trapped in heating system. • Purge air.
• Negative draft. • Incorrect vent size or blocked vent.
• Insufficient combustion air to boiler. • Check combustion and ventilation air
opening in boiler room meets installation
code requirements, and combustion air flow
openings in the boiler base and burner tray
are not blocked.
Gas odor.
• Leak in gas system. • See “What to do if you smell gas” on cover.
Have gas fitter test system and repair leaks.
• Carbon build up on the heat exchanger,
caused by improper venting, ventilation air
or low return water temperature.
• Have a qualified service technician inspect
and clean the heat exchanger and check and
adjust the system.
Flame roll out on ignition
or during operation.
• Negative draft. • Check venting.
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