Chapter 4 — Sequence of Operation
Part No. 750-184 4-3
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. 4, 5 and 6 oil only)
• Low gas pressures switch (LGPS)
• High gas pressure switch (HGPS)
• LE 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 lnterlock 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
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