28
TROUBLESHOOTING
WARNING
Electrical shock hazard. Turn OFF electrical power
supply at main power switch before servicing unit.
Service shall be preformed by a qualied service
agent. Failure to do so could result in death or
serious injury.
AT Boiler Trouble Shooting
Fault Possible Cause Corrective action
HL - High Limit Trip
Is circulator pump functional? If pump is not working replace.
Check temperature rise across boiler.
If > 20°F - Increase ow rate by using larger pump or
pipe size.
Check for temperature overshoot after
completion of heating cycle.
If greater than 10°F then increase differential setting.
Check that HL screw terminals on control board
are tight.
Are high limit switches open while water
temperatures less than 200°F (<200°F)?
Check high limit switches with Ohm meter. Replace high
limit(s) open.
Is heat load too small? Check heat load calculations.
AbP - Abnormal Power
Alarm
Power too high or too low?
Check Incoming power is between 197Vac and 240Vac
(197< IP <240Vac). If power outside range, contact
electrician to have power corrected.
Power is OK while unit is off but drops when unit
is on.
Check for adequate wiring and breaker size.
Water temperature
overshoots set point
temperature.
A small overshoot is normal, however if
overshoot is greater than 10°F (OS > 10°F)
then check the following.
Check temperature rise across boiler is less than 20°F.
If too high then increase ow rate through boiler, use
larger boiler pump if necessary.
Boiler is oversized for heating zone? Check heat load calculations.
Differential is too low? Increase differential temperature setting.
DFF - Dry Failure Alarm Air in boiler?
Purge boiler until all air is removed.
Check that adequate air vents located in critical system
high points. Add vents as necessary.
tSO, tSS -
Temperature sensor
failure.
Check resistance value of sensor using R/T
chart.
Good - Check for loose WT terminals on control board.
Bad - Replace Sensor.
CHF
Control Hardware Failure
Check for all wiring for damage or loose
connections.
Bad - Tighten any loose terminals. Replace Damaged
Wiring.
Good - Replace Control.
Circuit Beakers Trip
Inspect wiring for damage or short circuits.
Bad-Tighten any loose terminals. Replace damaged
wiring.
Inspect heating elements, Check element
resistance value is between 9-20Ω (Ohms).
Bad - Replace heating element(s).
Is current draw between 12 and 25A (Amps) per
element?
Bad - Replace heating element(s).
r1, r2, r3, r4
Relay failure code
Is heating element wiring loose or damaged?
Bad-Tighten any loose terminals. Replace Damaged
Wiring.
Is heat relay stuck closed?
With power removed check relay contacts with an Ohm
meter. Replace control if relay is stuck closed.
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