IBC VFC 15-150 User Manual

INSTALLATION AND OPERATION INSTRUCTIONS
5-8
VFC 15-150, VFC 45-225 MODULATING GAS BOILERS
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 4: Maximum Venting.
Incorrect settings or
defective thermostat.
Check operation. Refer to manufacturer’s
instructions. Check setting with ammeter.
Air in system or
marginal water ow.
Bleed/purge system as required. Conrm
adequate pump size and temp rise in HX
Slow combustion air
blower.
Check that CO2 level is OK per Tabel 8.
Dirty burner/heat
exchanger.
Check pressure drop.
Insufcient water
ow due to improper
piping.
Refer to recommended piping in Section 1.6
Insufcient water ow
due to undersized
pump.
Check manufacturer’s rating charts/check
temperature differential across heat exchanger.
Insufcient water ow
due to restrictions in
water pipe.
Check temperature differential across zone/heat
exchanger.
Insufcient radiation. Check actual amount of radiation per zone and
refer to manufacturer’s rating tables.
Unit over-red. 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.

IBC VFC 15-150 Specifications

General

Brand	IBC
Model	VFC 15-150
Category	Boiler
Language	English