57
Marvair GAA A/C w/Gas Heat I&O Manual
06/2023 Rev.5
5. Replace heat section access panel.
6. Turn on electrical power to the unit.
7. Set room thermostat to desired temperature.
8. On a call for heating, the air switch closes, initiating a 30 second pre-purge.
9. At end of pre-purge period, the Spark and Gas valve is energized for up to a 5 second ignition trial.
Gas valve will open.
10. Burners ignite and carryover.
11. Flame is detected by the flame sensor and control operates in a steady state condition.
12. Unit continues to heat until the room temperature set point is met.
If ignition is not achieved within 5 seconds, the gas valve is shut off, the inducer keeps running for an
interpurge period of 60 seconds and additional ignition trials follow the specified sequence. If after three
trials for ignition have occurred without proper ignition and flame detection, the control is locked out.
Control may be brought out of lockout by cycling the thermostat or turning the main power off for at least
5 seconds. Control will also attempt another ignition sequence after a one hour after a lock out occurrence.
13. If flame is lost once it has been established, the control will shut off the gas supply within 0.8
seconds and enter the interpurge period. Control will initiate up to 3 additional trials per normal
operation sequence.
14. If flame sensor indicates presence of flame during purge period, when no flame should be present,
the inducer will remain energized but the gas valve will not be energized until the cause of the “false
flame” is removed.
15. If the air pressure switch is closed when the inducer is energized or does not close after the inducer
is energized, the control will wait one minute for the air switch to open or close and then lock out.
16. If the control detects power to the gas valve when it should be off, or if no power when it should be
on, the control will go into lock out with all outputs off.
LED Flash Code
On- Steady
Control operation normal
1 Flash
Open pressure switch, limit switch or flame rollout switch
2 Flashes
Pressure switch stuck closed
3 Flashes
Ignition/flame sensor failure
4 flashes
Repeated flame losses
5 flashes
Internal control fault
6 flashes
Repeated pressure switch losses
