Cycling Problems - IBC SL 14-115 G3 Installation And Operating Instructions Manual

5.3.3 Cycling Problems

SYMPTOM
RAPID CYCLING
RAPID CYCLING
TROUBLESHOOTING
SL 14-115 G3, SL 20-160 G3, SL 30-199 G3 MODULATING GAS BOILERS SL 20-115 G2 MODULATING GAS BOILER
DIAGNOSIS
Improper values entered
via keypad.
Excess Condensate in
venting.
Obstruction in
condensate trap.
Improper vent length or
improper slope to vent.
Incorrect settings or
defective thermostat.
Air in system or marginal
water flow.
Slow combustion air
blower.
Dirty burner/heat
exchanger.
Insufficient water flow
due to improper piping.
Insufficient water flow
due to undersized pump.
Insufficient water flow
due to restrictions in
water pipe.
Insufficient radiation.
Unit over-fired.
Unit Oversized.
Improperly set or
defective operating/
safety controls.
REMEDY
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)
Check venting slopes on horizontal runs. Look for
sags.
Inspect and clean condensate trap.
Check venting. Compare vent length and diameter to
Table 3: Maximum Venting.
Check operation. Refer to manufacturer's instructions.
Check setting with ammeter.
Bleed/purge system as required. Confirm adequate
pump size and temp rise in HX
Check that CO level is within specification.
2
Check pressure drop.
Refer to recommended piping in Section 1.6
Check manufacturer's rating charts/check
temperature differential across heat exchanger.
Check temperature differential across zone/heat
exchanger.
Check actual amount of radiation per zone and refer
to manufacturer's rating tables.
Clock gas meter/check gas pressure with manometer/
check CO level.
2
Check load calculation vs. min. boiler output.
Check operation with ohmmeter/voltmeter.
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