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Installer’s Information Manual
overlap the burner-mounting flange of the adjacent
burner. See Figure 29.
6. Remove original gas orifices.
7. Carefully, hand thread new orifices into manifold. Do
not cross-thread. Tighten to torque of 50 inch-pounds.
8. Replace burners in reverse order, starting with the
burner closest to the gas control. Remember: burner-
mounting flange of burners farther from the gas control
overlap the burner mounting flange of the adjacent
burner.
Figure 29. Main Burner Removal.
9. Check burner carry-over alignment. Burner carry-overs
may touch but not overlap adjacent burner carry-overs.
Replace screws.
10. Turn gas control switch to “ON” position.
11. Open equipment shut-off valve in gas supply line just
ahead of furnace.
12. Set room thermostat to highest setting.
13. Turn on electricity at electrical disconnect switch
located next to furnace. Furnace will light.
14. Check for gas leaks using commercial soap solution
made for leak detection.
15. Check gas input following Section 17, "Checking Gas
Input Rate."
SECTION 21. ADJUSTING
BLOWER SPEED
Determine initial heating and cooling speeds in system
design stage. See Product Data Sheet for airflow data.
Depending on tests performed in following sections, you
may need to change blower motor speed.
CAUTION: Heating speed tap should not be reduced below
factory setting. Doing so may result in inadequate air
circulation, and could cause excessive air temperature rise
through furnace. This could cause a high-temperature limit
switch to cycle burners on and off, reducing furnace
efficiency and shortening life of heat exchanger and blower
motor.
Follow this procedure:
1. Turn off electricity at electrical disconnect switch
located next to furnace.
WARNING
: To prevent electric shock, turn off
electrical power to furnace before changing blower motor
speed.
2. All models have these four motor speed designations:
High Speed (HI)
Black wire
Medium High Speed (MH)
Blue wire
Medium Low Speed (ML)
Yellow wire
Low Speed (LO)
Red wire
3. To change cooling speed, move the desired motor lead
to the terminal marked 'COOL' on the Control. See
Figure 30. Initial factory setting for cooling is high
speed (black wire).
Figure 30. Main Blower Speed Selection.
4. To change the heating speed, move the desired motor
lead to the terminal marked 'HEAT' on the Control.
See Figure 30. Factory setting for heating is listed in
Table 10. Heating speed should not be reduced below
factory setting.
5. Connect the two unused motor leads to the terminals
marked "UNUSED MOTOR LEADS" or “PARK” on the
Control. See Figure 30.
WARNING
: Failure to properly terminate unused
motor leads could cause electrical shock.
6. Turn on the electricity at electrical disconnect switch
located next to furnace.
