Startup and Operation
4-2
750-392
CBEX-DE
The controls used vary depending upon the fuel burned and the requirements of applicable regulatory bodies.
Refer to the boiler wiring diagram to determine the actual controls provided. The circuits and controls normally
used are listed below and are referred to in the following sequence of operation. Components may vary.
To comply with requirements of insurance underwriters such as Factory Mutual (FM), XL GAP, or others, addi-
tional interlock devices may be used in addition to the circuits identified in section 4.2.
For additional information see the CB780E manual, 750-234.
Circuit Components/Controls
Limit Circuit
• Burner Switch (BS)
• Operating limit control (OLC) - pressure or temperature
• High limit control (HLC) - pressure or temperature
• Low-water cutoff (LWCO - Level Master)
• Gas-oil selector switch (GOS) - combination burner only
• Oil drawer switch (ODS) - oil/combination burner
• 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 Starter Circuit
• Blower motor starter (BMS)
• Combustion air proving switch (CAPS)
• Atomizing air proving switch (AAPS) - if provided
Running Interlock Circuit
• Blower motor starter interlock (BMSI)
• Combustion air proving switch (CAPS)
• Atomizing air proving switch (AAPS) - if provided
Running Interlock and Limit Circuit
• Low oil pressure switch (LOPS)
• High oil pressure switch (HOPS)
• High oil temperature switch (HOTS)
• Auxiliary low-water cutoff (ALWCO)
Pilot Ignition Circuit
• Gas pilot valve (GPV)
• Ignition transformer (IT)
• Gas pilot vent valve (GPVV) - if provided
Flame Detector Circuit
• Flame detector (FD)
• Main fuel valve circuit
• Man gas valve (MGV)
• Man gas vent valve (MGVV) - if provided
• Oil valve (OV)
• Main fuel valve light FVL)
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