CleaverBrooks CB - Circuit and Interlock Controls

Sequence of Operation
3-2
750-96 (revised 2010)
Model CB Packaged Boiler Manual
• Oil pump motor starter (if provided)
These sequences do not attempt to correlate the action of the fuel supply system or feedwater system except for
the interlock controls that directly relate to the action of the program relay. Chapters 4 and 5 contain operating
instructions and specific information on setting and adjusting the controls.
3.2 — Circuit and Interlock Controls
The burner control circuit is a two-wire system designed for 115 volt, single phase, 60 Hz, alternating current.
The electrical portion of the boiler is made up of individual circuits with controls that are wired in a manner
designed to provide a safe workable system. The program relay provides connection points for the interconnec-
tion of these various circuits.
The controls used vary depending upon the fuel—oil or gas—and the specific requirement of applicable regulatory
bodies. Refer to the boiler wiring diagram to determine the actual controls provided. The circuits and controls nor-
mally used in these circuits are listed below and referred to in the following sequence of operation.
Circuit Components
Limit Circuit
• Burner switch (BS)
• Operating limit control (OLC), pressure or temperature
• High limit control (HLC), pressure or temperature
• Low water cutoff (LWCO)
• Gas-oil selector switch (GOS), combination burner only
• Oil drawer switch (ODS), oil burner
• Low oil temperature switch (LOTS), No. 5 and 6 oil only
• Low gas pressure switch (LGPS)
• High gas pressure switch (HGPS)
• Fuel valve interlock circuit
• Main gas valve auxiliary switch (MGVAS)
• Oil valve auxiliary switch (OVAS)
Blower Motor Start Circuit
• Blower motor starter (BMS)
• Air compressor motor starter (ACMS), if provided
• Air purge valve (APV), No. 5 and 6 oil only
Running Interlock Circuit
• Blower motor starter interlock (BMSI)
• Combustion air proving switch (CAPS)
• Atomizing air proving switch (AAPS)
Low Fire Proving Circuit
• Low fire switch (LFS)
Pilot Ignition Circuit
• Gas pilot valve (GPV)
• Ignition transformer (IT)
• Gas pilot vent valve (GPVV), if provided