GAMA Gas-Fired Furnace, User'S Information Manual

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UNIT SEQUENCE OF OPERATION
Here's How Your Heating System Works:
Standby Mode
When the control is in standby mode, it continually
monitors thermostat input, rollout switch, and flame
sense.
Call For Heat
On a call for 1
st
stage heat (W1) from the room
thermostat, the ignition control performs a 1-second self-
check. The control verifies the limit switch is closed and
both low and high pressure switches are open. The
control always starts on low-fire and ignores 2
nd
stage call
for heat until low heat is established and heat blower on
delay is complete. The induced draft blower is energized
and waits for the low pressure switch to close before
starting a 15-second pre-purge period. Upon completion
of the pre-purge the hot surface igniter is energized for a
period of 7 seconds (15 seconds on retries) before the
gas valve is energized on 1
st
stage and main burners
ignite. After a 30-seconds blower "on" delay, the control
energizes the low heat circulating air blower. The blower
runs at reduced CFM (approximately 400 CFM) for 30
seconds than ramps up to 1
st
stage heat speed.
If 1
st
stage heating operation is not sufficient to satisfy
the heating demand, the room thermostat initiates a call
for 2
nd
stage heat (W1 and W2). The control confirms the
high-fire pressure switch contacts are closed and the gas
valve energizes on 2
nd
stage heat. The circulating air
blower then ramps up to 2
nd
stage heat speed.
When the 2
nd
stage call for heat is satisfied, the
control shuts off the gas valve and runs the combustion
air blower for a post purge period of 5 seconds. The
circulating air blower continues to run for approximately 3
minutes before ramping down. If the thermostat W2 call
ends and W1 remains, the control de-energizes the high
gas output, the gas valve drops back to 1
st
stage heat
and after approximately 2 minutes the circulating air
blower ramps down to 1
st
stage heat speed.
In the event the unit loses ignition, the control will
attempt to recycle up to five times before it goes into a 1-
hour lockout. Lockout may be manually reset by
removing power from the control for more than 1 second
or removing the thermostat call for heat for more than 3
seconds.
If during a heating cycle the limit control senses an
abnormally high temperature and opens, the ignition
control de-energizes the gas valve and the combustion
blower while the circulating blower ramps up to 2
nd
stage
heat speed. The circulating blower remains energized
until the limits are closed.
Should overheating occur, or the gas supply fail to
shut OFF, turn OFF the manual gas valve to the
appliance BEFORE turning OFF the electrical
supply. A failure to adhere to this warning can
result in a fire or explosion and bodily harm.
Fan "ON"
A call for continuous fan from the thermostat closes
R to G on the control board. The control waits for a 1-
second debounce delay before responding by energizing
the circulating air blower at 50% of the cooling speed.
When the call for fan is turned off, the control de-
energizes the circulating blower.
Cooling
A call for cooling from the thermostat closes R to Y
and R to G on the blower control board. The control
waits for a 1-second thermostat debounce delay before
energizing the circulating air blower to 82% of the cooling
speed. After 7.5 minutes, the circulating blower
automatically ramps up to 100% of the cooling speed.
When a call for cooling is satisfied, the circulating blower
ramps back down to 82% of the cooling speed for 60
seconds then shuts off.
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