Display Fail; No Config Key; Config Key Crc - A.O. Smith 100 Series Service Handbook

DISPLAYED MESSAGE/CONDITION/INDICATES

Display Fail

Communication between the MCB and UIM has been
interrupted - the MCB is unable to communicate with the
UIM.
Important Service Reminder:
When performing any troubleshooting steps outlined in
this manual always consider the wiring and connectors
between components. Perform a close visual inspection
of all wiring and connectors to a given component before
replacing any electrical part or component.

No Config Key

The 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 modulate blower speed during various
operating states, see Config Key on page 13.
If this key is not plugged into the J23 Socket on the
MCB circuit board the EMC 5000 Modulation Control
System will declare a fault condition and display this Error
Message on the UIM's LCD display.

Config Key CRC

Data read from the Config Key by the MCB was not
properly confirmed at power up.
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 modulate blower speed during various
operating states, see Config Key on page 13.
50 Servicing should only be performed by a Qualified Service Agent
CHECK/REPAIR
• Plug UIM Comm cable into the other Internal Comm
port on the MCB, see page 25.
• Check communication cable to the UIM. Turn off
power and Install a new/different communication
cable (standard Cat 5 network cable).
• Closely inspect communication ports on MCB and
UIM for damage or wear.
• Turn off power to the Boiler and install a new
communication cable (standard Cat 5/6 network
cable) between the UIM and the MCB's Internal
Comm Port, see page 25.
• Call the toll free support phone number on the back
cover of this manual for further assistance if the
problem has not been corrected after performing the
procedures outlined here.
• Ensure the Config Key is present and securely
plugged into the J23 Socket on the MCB circuit
board, see page 27.
• Closely inspect Config Key plug pins - if damaged
replace the Config Key for the correct Btu/hr model
and fuel type, see page 27. Call the toll free support
phone number on the back cover of this manual for
further assistance.
• Closely inspect the pins in the J23 Socket on the
MCB for signs of wear or damage, see page 27.
• Call the toll free support phone number on the back
cover of this manual for further assistance if the
problem has not been corrected after performing the
procedures outlined here.
• Ensure the Config Key is securely plugged into the
J23 Socket on the MCB circuit board, see page 27.
• Turn power off to the Boiler for 1 minute and then turn
power back on. Press the Select button on the UIM to
clear any error messages. This will provide the MCB
a second attempt to read and store data from the
Config Key.
• Closely inspect Config Key plug pins - if damaged
replace the Config Key for the correct Btu/hr model
and fuel type, see page 27. Call the toll free support
phone number on the back cover of this manual for
further assistance.
• Closely inspect the pins in the J23 Socket on the
MCB for signs of wear or damage, see page 27.
• Install a new Config Key for the correct Btu/hr model
and fuel type if this error message continues. Call the
toll free support phone number on the back cover of
this manual for further assistance.
• Call the toll free support phone number on the back
cover of this manual for further assistance if the
problem has not been corrected after performing the
procedures outlined here.