Goodman GSM Installation & Operating Instructions Manual page 23

This appliance is controlled by the thermostat via control voltage. It is the obligation of the installer to
educate the user on the proper use of the thermostat and the sequence of operation in both the
heating and cooling modes. It is also important that any repair or service be performed by a
QUALIFIED service person, not by the user.
HEATING MODE (W1 GSM ONLY)
• Main limit switch closed
• Thermostat calls for heat
• Vent motor starts- high speed
• W1 - Vent pressure switch closes
• Vent motor switches to low speed
• 15 second prepurge
• Ignition device activated
• 17 second warm-up period
• Gas valve opens on low fire
• Burners ignite and flame is sensed
• Blower starts on low speed 30 seconds after flame sense
• Furnace remains in operation until thermostat is satisfied
• Burners are extinguished
• Vent blower post purge
• Indoor blower shuts down after predetermined delay
HEATING MODE (GSMS ONLY)
• Main limit switch closed
• Thermostat calls for heat
• Vent motor starts
• Vent pressure switch closes
• 15 second prepurge
• Ignition device activated
• 17 second warm-up period
• Gas valve opens
• Burners ignite and flame is sensed
• Blower starts on low speed 30 seconds after flame sense
• Furnace remains in operation until thermostat is satisfied
• Burners are extinguished
• 30 second vent blower post purge
• Indoor blower shuts down after predetermined delay
COOLING MODE (GSM & GSMS)
• The control checks for an open limit. If an open limit is detected the furnace will remain inoperable
until the condition is corrected. During an open limit condition the circulating air blower will be
energized. The status light will blink four (4) times.
• A demand for cooling is initiated.
• The condenser contactor will close.
• After approximately seven (7) seconds the circulating air blower will start on the cooling speed.
• After the room thermostat is satisfied the condenser contractor will open.
• The circulating air blower will remain in operation for approximately sixty (60) seconds.
IO-176
SEQUENCE OF OPERATION
HEATING MODE W2 (GSM ONLY)
-
- Vent motor switches to high speed
-
-
-
- Operation continues until W2 is satisfied
23
Same operation as W1 until "blower starts"
operation
W2 pressure switch closes
Gas valve switches to high fire
Blower switches to medium speed
and furnaces switches to W1 operation