A.O. Smith TC-099 - Manual (Page 26)

AOS WPC - Tech Training 25 of 72 Ashland City, TN © 2007
Servicing should only be performed by a Qualified Service Agent
VF BOILER SERVICE MANUAL
MCB - MODULATING CONTROL BOARD - OVERVIEW
MCB / CCB / FCB Terminology Explanation
MCB and CCB are separate terms that refer to the same circuit board which is the main
controller for the EMC 5000 control system on VF boilers. MCB stands for “modulating
control board,” CCB stands for “central control board.” In VF boiler product literature MCB is
used to describe this component; in the UIM (pages 4 and 14) menu screens on VF boilers it
is referred to as the CCB. Some UIM menu screens show the term FCB (flame control
board). The FCB is a portion of the MCB that controls ignition. It is not a separate part.
The EMC 5000 control system is used on other products such as Genesis boilers that are
staged boilers and do not have modulating burners. However, this MCB circuit board is not
an interchangeable part with Genesis boilers.
VF boilers have a small circuit board (Daughter Board) attached to the MCB that houses the
J23 and J24 sockets. The VFD, Hall Effect sensor, and the Config Key are connected to
these two sockets (see pages 11-15 for more information on these components).
Daughter Board
Side View