LP-428 Rev. 6.6.16
51
24 VOLT LOW LOU
PUMP ON
LOU indicates the 24 volt power supply on
the control is damaged or overloaded. This
code resets automatically if it is the result
of an overload and the overload condition
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.
1. Check line voltage. It must be between 100 and 128 volts.
2. If available, connect a PC and use HTP 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-o 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.
WATER HIGH TEMP F00
PUMP ON
F00 indicates the water in the boiler has
overheated. The boiler will not restart until it
cools suciently and a technician determines
and repairs the cause of overheating and
pushes RESET on the display. This is a serious
safety issue as indicated by the illuminated
red light and the word LOCKOUT ashing
on the display. During this lockout fault, the
pump will be on in an eort to cool the boiler
down.
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.
Screen Description Possible Remedy
FLUE TEMP/WAT LV F01
PUMP ON
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 ue 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.
4. Blocked vent pressure switch (BVPS) – This
switch trips if there is excessive pressure in
the ue and automatically resets.
The following switches are optional
equipment that may be installed on
MODCON1000 and MODCON1700. 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 Cuto – This device trips
if the water level in the boiler is low and must
be manually reset.
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
o to the boiler and disconnect the switch to be tested from the
boiler to determine which one has tripped.
When you nd 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 ow
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 ue for blockage.
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