Cycling Issues - IBC VX Series Installation & Operating Manual

8.3.4 Cycling issues

Issue Diagnosis
Rapid Improper values
Cycling 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.
Low water flow due
to improper piping.
Low water flow due
to undersized pump.
Low water flow due
to restrictions in
water pipe.
Low radiation.
Appliance over-
fired.
Appliance
Oversized.
Improperly set or
defective controls.
Cycling issues
Check load maximum temps are above target temps, by ½ 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.
Check operation. Refer to manufacturer's instructions. Check
setting with ammeter.
Bleed/purge system as required. Confirm adequate pump size and
temp rise in the heat exchanger.
Check that CO level is within specification.
2
Check pressure drop.
Refer to recommended piping for the respective boiler model.
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.
Check load calculation vs. minimum boiler output.
Check operation with ohmmeter/voltmeter.
95
8.3.4 Cycling issues
Fix
2