Circuit and Interlock Controls for CB-Hawk boiler

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 interconnection of the 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 normally used in the circuits follow and are referred to in the following sequence of operation.

  • 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) - (Nos. 5 and 6 oil only)
    • Low gas pressures switch (LGPS)
    • High gas pressure switch (HGPS)
    • L E Proximity switch interlock
  • Fuel Valve Interlock Circuit:
    • Main gas valve auxiliary switch (MGVAS)
    • Oil valve auxiliary switch (OVAS) Blower Motor Starter Circuit
    • Blower motor starter (BMS)
    • Air compressor motor starter (ACMS) (if provided)
    • Air purge valve (APV) (Nos. 5 or 6 oil only)
  • Running Interlock Circuit:
    • Blower motor starter interlock (BMSI)
    • Combustion air proving switch (CAPS)
    • Atomizing air proving switch (AAPS) (if provided)
  • 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)
  • Flame Detector Circuit:
    • Flame detector (FD)
  • Main Fuel Valve Circuit:
    • Main gas valve (MGV
    • Main gas vent valve (MGVV) (if provided)
    • Oil valve (OV)
    • Main fuel valve light (FVL)
  • Firing Rate Circuit:
    • Damper motor transformer (DMT)
    • Modulating damper motor (MDM)
    • Manual-automatic switch (MAS)
    • Manual flame control (MFC)
    • Modulating control (MC)
  • High Fire Proving Circuit:
    • High fire switch (HFS)
  • 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)
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