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VF BOILER SERVICE MANUAL
AOS WPC - Tech Training 32 of 72 Ashland City, TN © 2007
Servicing should only be performed by a Qualified Service Agent
MCB - SECTION F
This section of the MCB contains the communication or “Comm” ports:
ICSP Port
The ICSP port (In Circuit Serial Programming) is used for programming the MCB board. DO NOT plug any
device or cable into this port.
This port is used by A. O. Smith engineering personnel only. Damage
caused by plugging cables/devices into this port would not be covered under warranty.
External Comm Ports (2)
These ports are used to connect external communication devices such as a modem or PC. These can also
be used to network boilers together using standard Category 5/6 network cable. One port would receive a
cable from the previous boiler and the second port would be connected to the next boiler in the network. Up
to 31 boilers can be networked (daisy chained) together in this way. For a boiler to be “seen” on the network
it’s default network address of 0 must be changed to a number between 1 and 31 in the User Settings menu
from the UIM. Each boiler on the network would need to have a different network address.
Internal Comm Ports (2)
These are parallel ports used to connect internal components that communicate with the MCB. One is
reserved for the UIM and the other would be used to connect to remote FCB circuit boards on products with
two or more stages of heating. Because these ports are parallel it does not matter which one connects to the
UIM.
JP1 Jumper
A jumper is installed between the two pins of JP1 on the MCB whenever an external communications
network/cable is longer than 2000 feet. On multiple boiler networks the jumper would be installed on the last
boiler only (furthest away) on the network. This jumper would not
be installed on any other boilers in the
network.
F
ICSP
JP1
External Comm Internal Comm
The MCB circuit board is mounted upside down on VF boilers compared to the illustrations below.