CYCLONE Xi COMMERCIAL GAS WATER HEATER
BTH 120 thru 500 SERVICE HANDBOOK
A.O. Smith – Technical Training Department 26 Ashl
and City, Tennessee © 2009
Servicing should only be performed by a Qualified Service Agent 316586-000
CONTROLS – CENTRAL CONTROL BOARD – CCB
The Central Control Board or CCB is contained
in the housing shown below. Access to the
board and the wiring harness plugs can be
accomplished by removing two Phillips screws
holding the cover.
The CCB is controlled by the settings given
through the desk top menu (UIM). The CCB also
monitors all pressure switches, the hot surface
ignitor, tank temperatures, the gas valve, the
anodes, and the flame sensor.
The CCB directly controls blower speed on the
BTH 199 and 250 models and indirectly controls
blower speed on the BTH 400 500 by means of a
Variable Frequency Drive (see page 38).
Note: Improper operation may be the result of a
loose connection. Please check all wiring
connections and the power supply to the water
heater.
This view shows the cover removed from the
CCB.
This is the back of the UIM.
Remove these
screws to release
cover
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