AAON M2-036 - Manual (Page 62)

62
burner and manifold pipe, or debris in the
main burner orifice. Soft brush or vacuum
clean affected areas after performing
Shutdown procedure.
2. Poorly defined, substantially yellow
flames, or flames that appear lazy, indicate
poor air supply to burners or excessive
burner input. Verify gas supply type and
manifold pressure with rating plate.
3. Poor air supply can be caused by
obstructions or blockage in heat exchanger
tubes or vent discharge pipe. Inspect and
clean as necessary by to eliminate blockage.
Vacuum any dirt or loose debris found in the
tubes or vents. Clean heat exchanger tubes
with stiff brush after performing Shutdown
procedure. Poor flame characteristics can
also be caused by undersized combustion air
openings or flue gas recirculation into
combustion air supply. Increase air opening
size or re-direct flue products to prevent re-
circulation.
4. Reduced air delivery can also be the result
of fan blade slippage, dirt accumulation the
fan blade or low voltage to draft inducer
motor. Inspect draft fan assembly and be
sure fan blade is secure to motor shaft.
Check line voltage to heater.
Shutdown
1. Set thermostat or controller to lowest
setting.
2. Turn off electrical supply to unit at
disconnect switch.
3. Turn off manual gas supply (supplied by
others).
4. Disconnect manifold and inlet pressure
taps and re-install pipe plugs.
5. Close module door.
Normal Operation
1. Turn on electrical supply to unit at
disconnect switch.
2. Turn on manual gas supply (supplied by
others).
3. Set Thermostat or Temperature controller
to desired temperature.
Figure 27 - Flame Sensor Current Check
Service Checks
Flame current is the current which passes
through the flame from the sensor to ground.
The minimum flame current necessary to
keep the system from lockout is 0.7
microamps. To measure flame current,
connect an analog DC microammeter to the
FC- and FC+ terminals per figure. Meter
should read 0.7 uA or higher. If the meter
reads below “0” on scale, meter leads are
reversed. Disconnect power and reconnect
meter leads for proper polarity.
Do not store or use gasoline or other
flammable vapors and liquids in the
vicinity of this or any other appliance.
WARNING