5-5
TROUBLESHOOTING
VFC 15-150, VFC 45-225 MODULATING GAS BOILERS
5.3 TROUBLESHOOTING GUIDE
SYMPTOM
DIAGNOSIS
REMEDY
AIRFLOW ERROR
Touch Screen Message:
Error – Low Air Flow
Low combustion airflow; soft
error; will retry in 5 minutes
Check fan operation
• Check lead is attached at fan.
• Cycle power off/on; listen for fan initialization.
If no action, focus your attention on the fan
itself.
Check for fouled
reference lines and air
sensor
• Check clear vinyl air reference lines below
gas valve for any sign of water. After
disconnecting from black sensor, blow clear.
Check for exhaust re-ingestion, or repeated
power interruptions .
• Ensure condensate trap is not blocked.
• Go to Advanced Diagnostics and check
differential air pressure sensor (at rest and
with fan on). See
Section 5.2.3
.
Check achieved fan
power
In Diagnostics, Fan Operation, during Pre-
purge, Fan Pressure (FP) should move close to
Required Pressure (RP); if FP only 480 to 600
vs. RP of 1,000 to 1,200, then check for actual
vent system blockage: (a) disconnect intake
within boiler case; (b) open burner then fan/gas
valve looking for debris.
Water noise in vent.
Excess condensate in
venting.
• Check condensate trap for obstructions.
Remove obstructions and refill condensate
trap with water.
• Check vent length, size and configuration,
particularly re: horizontal 2" piping.
WATERFLOW ERROR
Touch Screen Message:
Error - No Water Flow
Low water flow – soft error; will
retry in 5 minutes
Check pressure
sensors
• Check wiring: water pressure sensors to
controller.
• Check pressure sensors. See
Section 5.2.4
– 2nd paragraph.
Check for proper
piping
Refer to
Section 1.6 Water Piping
for
recommended piping installation.
Check primary pump
If there is a valve on the primary loop, close it
and listen for cavitation (evidence flow). If not,
go to Installer Setup; select pump purge “on” to
run pumps without a heat call - check for heat
buildup at pump body (indicates no flow).
Check for restriction
in water pipe
Check temperature differential across heat
exchanger at low –medium firing rate if possible.
Examine air strainer components for scale.
WARNING
Never attempt to repair
the control module (circuit
board). If the control module
is defective, replace it
immediately.
5.3.1 Using Control Module Errors Displayed
Summary of Contents for VFC 15-150
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