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LOU indicates the 24 volt power supply on
the control is damaged or overloaded. This
code resets automatically if it is the result
24 VOLT LOW
LOU
of an overload and the overload condition
PUMP ON
is removed. The second line indicates the
status of the pump. Note that while 24 volt
power is low, the pump output will be on.
F00 indicates the water in the boiler has
overheated. The boiler will not restart until it
cools sufficiently and a technician determines
and repairs the cause of overheating and
pushes RESET on the display. This is a serious
WATER HIGH TEMP F00
PUMP ON
safety issue as indicated by the illuminated
red light and the word LOCKOUT flashing
on the display. During this lockout fault,
the pump will be on in an effort to cool the
boiler down.
Screen
This code indicates that one of the safety
interlock switches present in the unit has
tripped. There are several interlock switches
that could possibly trip and cause this error.
The following four switches are installed and
are standard equipment in all boilers.
1. Flue ECO – Trips if the flue temperature is
excessive. This switch has to be manually
reset.
2. Boiler module thermal fuse – Trips if there
is excessive heat on the rear of the heat
exchanger.
3. Boiler module front temperature switch -
Trips if there is excessive heat on the front of
the heat exchanger.
FLUE TEMP/WAT LV F01
4. Blocked vent pressure switch (BVPS) – This
PUMP ON
switch trips if there is excessive pressure in
the flue and automatically resets.
The
equipment that may be installed on the
boiler. These devices have indicator lights
on them showing of they are tripped.
1. High gas pressure switch – This switch
trips if there is excessive gas pressure on
the outlet side of the gas valve and must be
manually reset.
2. Low gas pressure switch – This switch trips
if there is low gas pressure on the inlet side
of the gas valve and must be manually reset.
3. UL 353 Low Water Cutoff – This device trips
if the water level in the boiler is low and must
be manually reset.
whl-428-r1 Rev. 001 Rel. 012 Date 7.21.20
Description
following
switches
are
optional
1. Check line voltage. It must be between 100 and 128 volts.
2. If available, connect a PC and use Westinghouse service
software to check the 24v supply display in the lower left corner of
the screen. The number displayed here must be greater than 128
and should be no greater than 250. Use this as a troubleshooting
guide as you follow the steps below.
3. Remove the 10 pin Molex connector from the customer
connection board. If the message clears the problem is with
external sensor wiring. Examine the external sensor wiring for
shorts to the ground, repairing as necessary. If the message is still
present and the boiler is so equipped, disconnect the UL 353 low
water cut-off to see if the message clears. Replace the faulty part.
Check the low voltage wire harness in boiler for shorts to ground.
4. If a message only occurs when the burner tries to light, check
the gas valve for excessive current draw.
5. If a message is present when the low voltage harness is
disconnected from the 926 control board, replace the 926 control
board.
1. Check circulator pump operation.
2. If the circulator pump is running, ensure there is water in
the system and that the water is moving through the system as
intended. Ensure that all correct ball valves and or zone valves are
open or closed as intended.
3. Observe the temperature/pressure gauge. If the water is not too
hot and this message is displayed, check the wiring to the water
ECO sensor and repair if necessary. If the wiring is ok and this code
is still present and the water is not excessively hot, replace the ECO
sensor.
Possible Remedy
1. Check to see if the boiler with the F01 code displayed has any of
the optional switches installed.
2. If so, check to see if the indicator light on any of the devices is
showing that they are tripped.
3. If an indicator light is illuminated, investigate the source of the
error for that particular switch.
4. If there are no optional switches or none of the indicator lights
is illuminated on the optional switches then use an ohmmeter to
test each of the standard switches one at a time. Turn the power
off to the boiler and disconnect the switch to be tested from the
boiler to determine which one has tripped.
When you find the tripped switch investigate the cause of the fault
based on the purpose of the switch. NOTE: The common reasons
for the temperature switches to trip are a) low water flow through
the boiler, or b) poor heat transfer from the water to the load.
5. If no switches are tripped, push RESET on the boiler. If the boiler
tries to ignite or ignites and only runs for a short time and the F01
code returns, investigate the flue for blockage.
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