PRODUCT DESIGN
73
NORMAL SEQUENCE OF OPERATION
Goodman Two-Stage 80% or 90% Furnaces
White-Rodgers 50M56 Integrated Ignition Control
POWER UP
The normal power up sequence is as follows:
• 115 VAC power applied to furnace.
• Integrated control module performs internal checks.
• Integrated control module LED will light.
• Integrated control module monitors safety circuits con-
tinuously.
• Furnace awaits call from thermostat.
HEATING MODE
(MODE DIP SWITCH IS SET TO “1 STG” POSITION)
The normal operational sequence in heating mode is as fol-
lows:
• R and W thermostat contacts close, initiating a call for
heat.
• Integrated control module performs safety circuit checks.
• Induced draft blower is energized for 15 second prepurge
period causing pressure switch contacts to close.
• Igniter warm up begins after 15 second prepurge expires.
• Low and high stage gas valves open at end of igniter
warm up period, delivering gas to burners and establish-
ing flame.
• Integrated control module monitors flame presence. Gas
valve will remain open only if flame is detected.
• Circulator blower is energized on high heat speed fol-
lowing a fixed thirty second blower on delay. Electronic
air cleaner terminals are energized with circulator blower.
• Furnace operates; integrated control module monitors
safety circuits continuously.
• R and W thermostat contacts open, completing the call
for heat.
• Gas valve closes, extinguishing flame.
• Induced draft blower is de-energized following a fifteen
second post purge.
• The circulator blower remains at high heat speed for thirty
seconds. The circulator blower then switches to low heat
speed for the remainder of the selected heat off delay
period. For example, the selected heat off delay period
is 150 seconds. The circulator blower operates at high
heat for 30 seconds and at low speed for 150 - 30 = 120
seconds.
• Furnace awaits the next call from thermostat.
(MODE DIP SWITCH IS SET TO “2 STG” POSITION)
The normal operational sequence in sequence is as fol-
lows:
• R and W thermostat contacts close, initiating a call
for heat.
• Integrated control module performs safety circuit
checks.
• Induced draft blower is energized for 15 second
prepurge period causing pressure switch contacts to
close.
• Igniter warm up begins after 15 second prepurge ex-
pires.
• Low and high-stage gas valves open at end of igniter
warm up period, delivering gas to burners and estab-
lishing flame.
• High-stage gas valve closes after five seconds; low-
stage gas valve remains open.
• Integrated control module monitors flame presence.
Gas valve will remain open only if flame is detected.
• Circulator blower is energized on low heat speed fol-
lowing a fixed thirty second blower on delay. Electronic
air cleaner terminals are energized with circulator
blower.
• Furnace is now operating in low-stage heating mode.
• Furnace operates; integrated control module monitors
safety circuits continuously.
• If low-stage delay period expires, control will shift op-
eration from low-stage heating mode operation to high-
stage heating mode operation. Control will energize cir-
culator blower high heat speed and high stage gas valve.
• Furnace is now operating in high-stage heating mode.
• R and W thermostat contacts open, completing the
call for heat.
• Induced draft blower is de-energized following a fifteen
second post purge.
• Circulator blower is de-energized following a heat off
delay period (selectable 100 or 150 seconds; factory
set at 150 seconds).
If the furnace is operating in the low-stage heating
mode when thermostat contacts open, circulator re-
mains at low heat speed for the selected delay off pe-
riod.
If the furnace is operating in high-stage heating mode
when the thermostat contacts open, the circulator blower
remains at high heat speed for thirty seconds. The cir-
culator blower then switches to low heat speed for the
remainder of the selected heat off delay period. For
example, the selected heat off delay period is 150 sec-
onds. The circulator blower operates at high heat for 30
seconds and at low speed for 150 - 30 = 120 seconds.
• Furnace awaits the next call from thermostat.
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