5-9
TROUBLESHOOTING
SL 20-115 MODULATING GAS BOILER
SYMPTOM
DIAGNOSIS
REMEDY
RAPID CYCLING
Insufficient water flow
due to undersized
pump.
Check manufacturer’s rating charts/check
temperature differential across heat exchanger.
Insufficient water flow
due to restrictions in
water pipe.
Check temperature differential across zone/heat
exchanger.
Insufficient radiation.
Check actual amount of radiation per zone and
refer to manufacturer’s rating tables.
Unit over-fired.
Clock gas meter/check gas pressure with
manometer/ check Co2 level.
Unit Oversized.
Check load calculation vs. min. boiler output.
Improperly set or
defective operating/
safety controls.
Check operation with ohmmeter/voltmeter.
5.3.4 Temperature Problems
SYMPTOM
DIAGNOSIS
REMEDY
INSUFFICIENT HEAT
Operating
temperature too low.
increase temperature target.
See Section 2.7
Priority parameters
or load configuration
improperly set up.
Review load configuration parameters.
See
Section 2.7
Unit undersized.
refer to load Calculation vs. Boiler output.
Air trapped within
system.
Bleed system as required.
Improper system
piping.
refer to recommended piping in
Section 1.6
System pump
undersized.
Check pump manufacturer’s data/check temp
differential across heat exchanger.
Poor gas/air mixing.
Check Co2 level.
Defective thermostat.
refer to manufacturer’s instructions.
Obstruction in
condensate drain.
inspect and clean condensate drain.
Unit cycling on
operating/ safety
controls.
Check operation with ohmmeter/Voltmeter.
System radiation
undersized.
Check manufacturer’s rating tables for capacity
per foot.