IBC Technologies Inc.
47
VFC 15-150 and VFC 45-225
4.3.4 Detailed System Checks
Detailed Systems Troubleshooting
Cycling Problems
Symptom
Diagnosis
Remedy
Rapid Cycling
Primary cause ……….
Improper values entered via
keypad.
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)
ii) Water noise in exhaust
venting
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.
•
Improper slope to vent.
Check venting. Compare vent
length and diameter to
Table 3-
Maximum Venting
.
no other symptoms
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 CO
2
level is OK
9.0% nat. gas (10.2% for
propane)
Dirty burner/heat exchanger. Check pressure drop.
Insufficient water flow.
•
Improper piping.
Refer to recommended piping in
S
ection 1.5
.
•
Undersized pump.
Check manufacturer’s rating
charts/check temperature
differential across heat
exchanger.
•
Restriction 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
CO
2
level.
Unit Oversized.
Check load calculation vs. min.
boiler output
Improperly set or defective
operating/safety controls
Check operation with
ohmmeter/voltmeter
