Config Key - A.O. Smith 100 Series Service Handbook

CONFIG KEY

The Config Key is an 18" long cable with a plug on one end and an EEPROM memory chip sealed at the
other. The Config Key plugs into the J23 socket on the MCB, see MCB - Section H on page 27. The memory
chip contains blower speed programming data specific to the input Btu/hr and fuel type for each VF Boiler.
VF Boilers are available in natural and propane gas and in five input Btu/hr models ranging from 500,000 to
2,000,000. This Service Manual covers the 1,500,000 and 2,000,000 Btu/hr models only.
Each time the Boiler is powered up the MCB reads and then stores the blower speed programming data
from the Config Key into it's own internal memory. The MCB then uses the data to modulate the Combustion
Blower speed by sending instructions from the MCB J24 socket to the 5 pin socket on the Combustion Blower
Assembly, see Figure 4 on page 10 and MCB - Section H on page 27. Modulating the Combustion Blower speed
also modulates the firing rate on VF Boilers, see Venturi & Gas Train on page 12.
There is a label at the end of the Config Key cable near the memory chip that identifies which boiler model it is
used for. This end of the cable is threaded into the wiring chase during manufacturing. The software revision
for the Config Key can be viewed in the Log & System Info menu, see Control System Menus on page 44.
WARNING:
Config Keys are manufactured for a particular fuel type and input Btu/hr rating as described above. Config
Keys MUST NOT be interchanged in the field for any reason. Doing so can cause ignition failure, rough
starting/operation and poor combustion. Changing a Config Key can permanently damage the Boiler, cause
property damage, personal injury or death. Damage to the Boiler caused by interchanging Config Keys in the
field is not covered under the limited warranty as this would be considered a field alteration of the Boiler's
design.
If it is suspected the Config Key is defective or the Boiler is experiencing ignition failure, rough starting/
operation and/or poor combustion, ensure the proper Config Key is installed. Navigate to the Log & System
Info menu in the control system and record the kBTU Rating, Fuel Type and Config Key Rev number, see
Control System Navigation on page 40 and Control System Menus on page 44. If the Fuel Type and/or kBTU
rating listed in the Log & System Info menu does not match the rating plate on the Boiler, turn the Boiler off
and disable Boiler operation. Call the toll free support phone number on the back cover of this manual for
further assistance.
Figure 7
Servicing should only be performed by a Qualified Service Agent 13