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AOS WPC - Tech Training 43 of 72 Ashland City, TN © 2007
Servicing should only be performed by a Qualified Service Agent
VF BOILER SERVICE MANUAL
ERROR MESSAGES (CONT)
DISPLAYED MESSAGE
CONDITION/INDICATES
CHECK/REPAIR
“Display Fail”
Communication between the MCB and UIM has
been interrupted - the MCB is having trouble
communicating with the UIM.
Important Service Reminder:
When performing any troubleshooting steps outlined
in this service manual always consider the wiring
and connectors between components. Perform a
close visual inspection of all wiring and connectors
to a given component before replacement.
Ensure wires were stripped before being crimped in
a wire connector, ensure wires are crimped tightly in
their connectors, ensure connection pins in sockets
and plugs are not damaged or worn, ensure plugs
and sockets are mating properly and providing good
contact.
Failure to perform this critical step or failing to
perform this step thoroughly often results in
needless down time, unnecessary parts
replacement, and customer dissatisfaction.
• Plug UIM comm cable into the other “internal”
comm port on the MCB. (see page 32)
• Check comm cable to the UIM. Turn off power
and Install a new/different comm cable
(standard Cat 5 network cable).
• Inspect both internal communication ports on
MCB and UIM for damage or wear. Repair or
replace any components that are worn or dam-
aged.
“No Config Key”
MCB does not recognize the presence of a Config
Key at MCB socket J23.
The Config Key contains model specific (Btu/hr &
fuel type) blower speed programing data. This data
is written to the MCB’s internal memory at power up.
The MCB then uses this data to instruct the VFD
(variable frequency drive) to modulate blower speed
during various operating states.
If this key is not plugged into the J23 socket on the
MCB circuit board the EMC 5000 control system will
declare a fault and display this error message on the
UIM.
• Ensure the Config Key is present and securely
plugged into the J23 socket on the MCB circuit
board (see pages 14 and 34).
• Closely inspect Config Key plug pins - if dam-
aged Install a new Config Key for the correct
Btu/hr model and fuel type.
• Install a new Config Key for the correct Btu/hr
model and fuel type.
• Closely inspect the pins in the J23 socket on the
MCB for signs of wear or damage.