INSTALLATION
SECTION 3- DIRECT-VENT, MULTIPOISE, HOT-SURFACE IGNITION, SINGLE-STAGE, TWO-STAGE AND VARIABLE-SPEED
CONDENSING FURNACES
PROCEDURE 1—INSTALL MAIN BURNER ORIFICES
NOTE:
See Fig. 26 or 27 for component location in upflow orientation. Reorient component arrangement when furnace is installed in other
positions.
1. Turn off furnace gas and electrical supplies.
2. Remove main furnace door.
3. Turn furnace gas valve switch to OFF position.
4. Remove burner enclosure front.
5. Remove gas supply pipe from gas valve.
6. Remove wires from gas valve. Note location for reassembly.
CAUTION: UNIT OPERATION HAZARD
Wiring errors will cause improper and dangerous operation. Label all wires prior to disconnection when servicing controls.
ATTENTION: D’EQUIPEMENT DANGER D’OPERATION
Toute erreur de câblage peut être une source de danger et de panne. Lors des opérations d’entretien des commandes, étiqueter tous
les fils avant de les déconnecter.
7. Remove burner-box pressure tube from gas-valve burner enclosure; reference pressure-tap fitting. (See Fig. 27.)
8. Remove screws that secure manifold to burner box and remove manifold, orifices, and gas valve as 1 assembly.
9. Remove and discard orifices from manifold.
10. Refer to conversion kit rating plate #327697-201 to determine main burner orifice size. (See Fig. 25.)
Furnace gas input rate on rating plate is for installations at altitudes up to 2000 ft. In the U.S.A., the input rating for altitudes above 2000 ft must
be reduced by 2 percent for each 1000 ft above sea level.
In Canada, the input rating must be derated by 5 percent for altitudes of 2000 ft to 4500 ft above sea level.
The Conversion Kit Rating Plate accounts for high altitude derate.
11. Install main burner orifices. Do not use Teflon tape. Finger-tighten orifices at least 1 full turn to prevent cross threading, and then tighten
with wrench. There are enough orifices in each kit for the largest furnace. Discard extra orifices.
CAUTION: UNIT DAMAGE HAZARD
Failure to follow this caution may result in excessive burner noise and misdirection of burner flames. This may result in flame
impingement of the burners and the heat exchangers, causing failures.
DO NOT re-drill burner orifices. Improper drilling may result in burrs, out-of-round holes, etc. Obtain new orifices if orifice size must
be changed. (See Fig. 1.)
NOTE:
DO NOT reinstall the manifold, orifices, gas-valve assembly, and burner enclosure front at this time.
PROCEDURE 2—REPOSITION AIR SHUTTER (VARIABLE SPEED 355MAV060120 AND 58MVP120-20 ONLY)
1. Remove 2 screws holding air shutter in natural gas usage (NAT) position.
2. Reposition air shutter to propane gas usage (PROP) position. (See Fig. 18.) Screws will now be located in the shutter next to the PROP
stamp.
NOTE:
Air opening above burners will now be partially obstructed by air shutter.
PROCEDURE 3—INSTALL DIVERTER PLATE (TWO-STAGE AND VARIABLE SPEED CONDENSING FURNACES ONLY)
Install diverter plate (provided in kit) above combustion air intake box as follows:
1. Remove front 2 screws on combustion air intake box. (See Fig. 19.)
2. Remove combustion air intake box and set aside. (See Fig. 19.)
3. If air diffuser has a solid center, remove center section of air diffuser.
a. Remove burners.
SINGLE STAGE MODELS
TWO-STAGE MODELS
VARIABLE SPEED MODELS
58MXA
350MAV
PG9MAA
58MTA
352MAV
58MVP
355MAV
58MCA
340MAV
490AAV
58MSA
345MAV
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