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need to purge air from the manifold at start-up. If ignition does not
occur on the first trial, the gas and spark are shut off by the igni-
tion control and the control enters an inter-purge period of 15 sec-
onds, during which the draft inducer continues to run. At the end
of the inter-purge period, another trial for ignition will be initiated.
Control will initiate up to three ignition trials on a call for heat be-
fore lockout of control occurs. Control can be brought out of lock-
out by turning thermostat or controller to its lowest position, wait-
ing 5 seconds, and then turning back up to call for heat. Controls
will automatically reset after one hour and initiate a call for heat.
Manifold Pressure Adjustment (Duct and Rack System Fur-
naces)
A pressure tap is provided in each furnace manifold for measuring
the gas manifold pressure. Manifold pressure must be checked at
start-up and during any service or maintenance. All control sys-
tems require a manifold pressure of 3.40 to 3.50 in. wg at maxi-
mum input rating on natural gas, and 10.0 in. wg on propane gas
at maximum input rating. See Fig. 150-152 on page 193 for gas
valve adjustment locations.
NOTE: For two-stage and modulating control applications, verify
proper low fire adjustments as outlined in the Sequence of Opera-
tion document provided in the instruction package. Check the fur-
nace section for this document or contact your Carrier service
representative.
Burner Flames (Duct and Rack System Furnaces)
Before completing the start-up, check the appearance of the main
burner flame.
1. The burner flame should be predominately blue in color, and
well-defined and centered at the tube entry as shown in
Fig. 180. Distorted flame or yellow tipping of natural gas
flame, or a long yellow flame on propane, may be caused by
lint and dirt accumulation inside burner or at burner ports, at
air inlet between burner and manifold pipe, or debris in the
main burner orifice. Soft brush or vacuum clean affected
areas.
2. Poorly defined, unfocused, substantially yellow flames, or
flames that appear weak or wavering, indicate poor air sup-
ply to burners or excessive burner input. Verify gas supply
type and manifold pressure with rating plate.
Poor air supply can be caused by obstructions or blockage in heat
exchanger tubes or vent discharge pipe. Inspect and clean as nec-
essary to eliminate blockage. Vacuum any dirt or loose debris.
Clean heat exchanger tubes with stiff brush.
Poor flame characteristics can also be caused by undersized com-
bustion air openings or flue gas recirculation into combustion air
supply. Increase air opening size or re-direct flue products to pre-
vent re-circulation.
Reduced air delivery can also be the result of fan blade slippage,
dirt accumulation on 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.
Fig. 180 — Proper Flame Appearance
Normal Operation (Duct and Rack System Furnaces)
1. Turn on electrical supply to unit at disconnect switch.
2. Turn on manual gas supply.
3. Set thermostat or temperature controller to desired tempera-
ture.
Information outlining the normal sequence of operation and wir-
ing diagram for the control system supplied with the furnace mod-
el is located in the furnace section, or contact your Carrier service
representative.
Shutdown (Duct and Rack System Furnaces)
1. Set thermostat or controller to lowest setting.
2. Turn off electrical supply to unit at disconnect switch.
3. Turn off manual gas supply.
4. Disconnect manifold and inlet pressure taps and re-install
pipe plugs.
5. Replace vestibule access panel or close door.
Energy Recovery Wheel
Keep hands away from rotating wheel. Contact with rotat-
ing wheel can cause physical injury.
1. By hand, turn the wheel clockwise (as viewed from the
pulley side), to verify that the wheel turns freely through a
full 360-degree rotation.
2. Before applying power to the drive motor, confirm that
the wheel segments are fully engaged in the wheel frame
and that the segment retainers are completely fastened.
(See Fig. 181.)
3. With hands and objects away from moving parts, activate
the unit and confirm wheel rotation. The wheel rotates
clockwise (as viewed from the pulley side).
4. If the wheel has difficulty starting, turn the power off and
inspect for excessive interference between the wheel sur-
face and each of the four (4) diameter seals. To correct,
loosen the diameter seal adjusting screws and back ad-
justable diameter seals away from the surface of the
wheel, apply power to confirm that the wheel is free to ro-
tate, then re-adjust and tighten the hub and diameter seals
according to the instructions in the Service section.
5. Start and stop the wheel several times to confirm seal ad-
justment and to confirm that the belt is tracking properly
on the wheel rim (approximately 1/4 in. from outer edge
of rim).
SEGMENT
RETAINER
CATCH
a39-2379
A48-
ZEROING THE MINIHELIC GAGE BEFORE START UP
If the Minihelic
stallation, it may need to be zeroed before placing in operation. If
1. Minihelic is a registered trademark of Dwyer Instruments Inc.
210
CAUTION
2
ROTATE AWAY
FROM WHEEL RIM
1
PUSH
TOWARD
CENTER
WHEEL RIM
Fig. 181 — Segment Retainer
gage needs to be removed or replaced, after in-
1
SPOKE
CENTER OF
WHEEL
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