INSTALLATION AND OPERATION INSTRUCTIONS
5-8
SL 20-115 MODULATING GAS BOILER
5.3.3 Cycling Problems
SYMPTOM
DIAGNOSIS
REMEDY
RAPID CYCLING
Improper values
entered via keypad.
Check load maximum temps are above target
temps, by 1/2 of the selected boiler differential.
ensure boiler differential is oK (16-30°F is
generally adequate)
Excess Condensate in
venting.
Check venting slopes on horizontal runs. look
for sags.
Obstruction in
condensate trap.
inspect and clean condensate trap.
Improper vent length
or improper slope to
vent.
Check venting. Compare vent length and
diameter to
Table 3: Maximum Venting.
Incorrect settings or
defective thermostat.
Check operation. refer to manufacturer’s
instructions. Check setting with ammeter.
Air in system or
marginal water flow.
Bleed/purge system as required. Confirm
adequate pump size and temp rise in HX
Slow combustion air
blower.
Check that CO2 level is within specification.
Dirty burner/heat
exchanger.
Check pressure drop.
Insufficient water
flow due to improper
piping.
refer to recommended piping in
Section 1.6
SYMPTOM
DIAGNOSIS
REMEDY
bOILER WILL NOT ATTEMPT
TO IGNITE. FAN AND PUMP
ARE OPERATING NORMALLY.
No power to ignition
control module.
•
Check system wiring.
•
Check air reference tubing.
Igniter probe/flame
sensor disconnected.
reconnect probe.
Defective Control
Module.
Check ignition output from control module.
bOILER WILL NOT ATTEMPT
TO IGNITE. FAN AND / OR
PUMP ARE OFF DISPLAY
NOT ILLUMINATED
No power to boiler.
Check line voltage .
Defective transformer.
Check transformer. reconnect or replace as
needed.