5-3
TROUBLESHOOTING
VFC 15-150, VFC 45-225 MODULATING GAS BOILERS
5.2.2 Fan/Blower
Operating power is provided by means of a separate 120 VAC connector at
the back of the fan (white/black/green). Control of the fan is provided via a four
lead connector at the front of the fan. This connector feeds a PWM control
signal (black wire) from the controller and provides a tachometer signal (white
wire) back from the fan. Unplugging the connector will cause the fan to go to
high speed and trigger a “Blocked Vent Error” within 6 seconds if the boiler is
operating.
LEAD COLOR
FUNCTION
TROUBLESHOOTING
Red
35 VDC Positive power
terminal
Fan will only operate at max. speed
if disconnected.
Blue
35 VDC Negative power
terminal
Fan will only operate at max. speed
if disconnected.
Black
Signal from controller
Fan will only operate at max. speed
if disconnected.
White
Fan tach.
2 pulses/rev (freq x 30=rpm)
Table 11: Fan Operation
5.2.3 Differential Air Pressure Sensor
Do not blow into the ports of the sensor, this is not a switch and “does not
click when closed”. Excessive pressure will damage the sensor thus requiring
replacement. The sensor values are located in the advanced diagnostics section
of the controller. In general, the Fan Pressure and the Required Pressure
should be very close to each other while the boiler is in operation. If the required
pressure is higher than the actual pressure there are several possible causes.
•
Exhaust and/or Air Intake piping installed longer that allowed
•
Improper grading of the Exhaust and/or Air Intake piping allowing condensate
to be trapped in the piping
•
Re-Ingestion of flue gasses has caused the Swirlplate and/or Fan Impeller to
erode, becoming ineffective.
•
Air Pressure Sensor tubing not correctly attached.
If the Differential Air Pressure Sensor replacement is required, ensure the
replacement sensor is IBC part# 240-003 (and specifically that it is
not
a similar-
looking part marked for use only on the SL 28-160 model boiler). Use of any
other differential air pressure sensor is forbidden.
5.2.4 Water Pressure Sensor
The water pressure sensor ensures there is adequate pressure in the heating
system for safe operation. The pressure is displayed in PSI as the default. If the
system pressure should drop below 8PSI the firing rate of the boiler is reduced.
If the pressure drops to 4PSI or lower, the boiler will not fire.
Check operation of the sensor by isolating the boiler from its system piping,
closing the system fill valve then cracking the pressure relief valve; the pressure
displayed should reflect declining pressure. If it remains “fixed”, drain boiler and
replace sensor, or dislodge any blocking debris from sensor inlet channel and
reinsert.
Control wire plug
Unplug to run fan full speed
Air pressure sensor mounting
Summary of Contents for VFC 15-150
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Page 75: ...NOTES...
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