Service manual

SC Series Boilers – Installation and Service Manual
34
Troubleshooting Guide Section 8
8.1 Possible Causes and Solutions
Problem Possible Cause Solution
• No
p
ower.
•
Check
p
ower switches and wirin
g
.
• 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.
• 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.
• Faulty wiring.
• Check wiring of aquastats, zone valves, and
thermostats for loose or broken wires and
repair.
• Fault
y
a
q
uastat, thermostat, or zone valve.
•
Check and re
p
lace if necessar
y
.
• Pressure switch failure or airflow blockage
in heat exchanger, venting, air inlet pipe or
termination.
• Check pressure switch and replace if
necessary. Remove airflow blockages.
Boiler will not fire.
• Fault
y
controller or control wirin
g
.
•
See "Control trouble troubleshootin
g
".
• 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
(
o
p
en
p
osition
)
.
•
Check
g
as valve, re
p
lace if necessar
y
.
• Faulty wiring.
• Check wiring of aquastats, zone valves, and
thermostats for short circuits or incorrect
wiring.
Boiler fires continuously.
• Fault
y
a
q
uastat, zone valve or thermostat.
•
Check and re
p
lace if necessar
y
.
• 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.
• Flue leakin
g
.
•
Check ventin
g
and boiler if leakin
g
.
• Insufficient combustion air to boiler.
• Check combustion and ventilation air
opening in boiler room meets installation
code requirements, and air differential
pressure if too low.
Gas odor.
• Leak in gas system.
• See “What to do if you smell gas” on cover.
Have gas fitter test system and repair leaks.
• Burner cracked or eroded
•
Check & re
p
lace if necessar
y
.
• Not enough combustion air or wrong air
switch setting
• Adjust air shutter & check air switch
condition
Flame flash back
• The vent or air inlet blocked • Check & clean