Control Panel - A.O. Smith 100 Series Service Handbook

CONTROL PANEL

Figure 10 shows the Control Panel layout inside the VF Boiler. Three pressure switches are located in
the upper right corner. Directly beneath the pressure switches is the Pump Relay that energizes factory
installed Boiler Circulation Pumps or field supplied 120 VAC pumps up to 1 horsepower. For higher voltage/
horsepower pumps a field supplied starter must be used. The black and white 120 VAC pump wiring in the
junction box on the back of the Boiler would be used to power the field supplied starter coil in this case. The
MCB (Modulation Control Board) and the PDB (Power Distribution Board are also located on the Control
Panel. The optional LWCO (Low Water Cut Off) circuit board is mounted on the Control Panel on models so
equipped.
MCB
(Modulation Control Board)
Servicing should only be performed by a Qualified Service Agent
PRESSURE SWITCHES
BLOCKED FLUE BLOCKED
(EXHAUST) INTAKE AIR
BOILER
CIRCULATION
PUMP RELAY
(Power Distribution Board)
Figure 10
BLOWER
PROVER
LWCO CIRCUIT BOARD
(Low Water Cut Off)
PDB
ON/OFF
POWER RELAY
17