CHAPTER3
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 frre switch (LFS)
Pilot Ignition Circuit
Gas pilot valve (GPV)
•
Ignition transfonner
(I1)
Gas pilot vent valve (GPVV)
(if
provided)
Flame Detector Circuit
Flame Detector (FD)
Main Fuel Valve Circuit
• Main gas valve (M:GV)
•
Main gas vent valve (M:GVV)
(if
provided)
• Oil valve (OV)
Main fuel valve light (FVL)
Firing Rate Circuit
Damper motor transfonner (DMT)
Modulating damper motor
(MOM)
Manual·automatic switch (MAS)
Manual flame control (MFC)
750-150
SEQUENCE OF OPERATION
• Modulating control (MC)
To
comply with requirements
of
insurance un-
derwriters such as Factory Mutual (F.M.), In-
dustrial Risk Insurers (I. R.I.)
or
others, additional
interlock devices may
be
used in addition to those
mentioned above.
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
(AL WCO)
C.
SEQUENCE
OF
OPERATION
-
OIL.
OR
GAS
On
a combination fuel unit, the gas/oil switch
must
be
set for the proper fuel.
The
following
sequence
occurs
with
power
present at the program relay (PR) input tenninals
and with all other operating conditions satisfied:
Pre-Purge Cycle - When the burner switch
(BS) is turned
"on,"
and controls wired in the
"limit" and "fuel valve interlock" circuits are
closed and no flame signal
is
present, the "blower
motor start circuit"
is
powered energizing the
blower motor starter
(BMS). The load demand
light (LDL) turns on. When firing oil, the air
compressor motor starter (ACMS)
(if provided)
is
also powered. The air purge valve (APV) (No.
5 and 6 oil only) remains de..energized.
At the same time, the program relay signals the
modulating damper motor
(MOM) to open the air
damper. The damper begins to open and drives
CHAPTER 3-7
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