Mode Of Operation - Thermo Pride MHA1-50N Installation And Service Manual

All installations and services must be performed by qualified service personnel.

Mode of Operation

Main Burner
Operation
Repeated Trials
for Ignition.
Call for Heat
Satisfied
System Lockout
End of Cycle
Control System Action
After delay-to-fan-on period
ends, circulating air fan is
energized at heating speed.
The (optional) electronic air
cleaner and humidifier are
energized.
When thermostat is satisfied,
contacts open and the gas
valve is de-energized. After
proof of flame loss, inducer
and (optional) humidifier are
de-energized. The
delay-to-fan-off period begins
(180 seconds)
After the delay-to-fan-off
period ends, the circulating
air fan and {optional)
electronic air cleaner are
de-energized.
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If ignition attempt is unsuccessful,
one more retry will be made before
the ignition control module goes into
system lockout.
If flame is detected,then lost,
the ignition control module will
repeat the initial ignition sequence
for a total of four recycles. After
four unsuccessful recycle attempts,
the control will go into system lockout.
The ignition control module will reset
automatically in 60 minutes.
If system is in lockout, try to
reset by interrupting the power
to the furnace at the disconnecting
switch or interrupting the call for heat
at the thermostat. If this does
not restart the system, refer to
the troubleshooting section of
this manual.