Blower Speed Adjustment - Lennox LGA Series Unit Information

4-Blower Speed Adjustment

To Change Blower Speed:
(208/230V Direct-Drive Units)
1- Referring to blower performance tables in front of this
manual, use the static pressure and blower speed tap to
determine unit CFM.
2- Turn off electric power to unit.
3- Remove blower access door.
4- Disconnect blower motor harness from motor.
5- Select desired speeds for heating and cooling. (Pin 6 =
Low, Pin 5 = Med-Low, Pin 4 = Medium, Pin 3 = Med-High,
Pin 2 = High).
6- Depress harness connector tab to release wire terminal
(J43). Select connector location for new speed (refer to
unit wiring diagram). Insert wire terminal until it is securely
in place. See figure 10.
7- Replace harness connector to motor .
BLOWER SPEED TAP SELECTION
DEPRESS TAB TO RELEASE
WIRE TERMINAL. SELECT
CONNECTOR LOCATION
FOR NEW SPEED (REFER
TO UNIT WIRING DIAGRAM).
INSERT WIRE UNTIL IT IS
SECURELY IN PLACE.
FIGURE 10
To Change Blower Speed:
(460V and 575V Direct-Drive Units)
1- Referring to blower performance tables in front of this
manual, use the static pressure and blower speed tap to
determine unit CFM.
2- Turn off electric power to unit.
3- Remove blower access door.
4- Disconnect J38 plug from P38.
5- Table 3 shows the speeds associated with each cap plug
in the harness. Choose the blower speed desired and
make appropriate cap plug changes.
6- Insert new plug until securely in place.
J43
HARNESS
CONNECTOR
P43
MOTOR
Page 21
TABLE 3
Leadless 460V Blower Motor Speed Plug (J38)
Cooling
Cooling Heating
Low Low
Med Low
Med Med
CAUTION
Motor can be damaged if speed change is made im-
properly. Use table 3 as a guide and remember:
Black Lead = Speed Tap
Orange Lead = Common
Blue Lead = Internal circuit, connected to high
speed (pin 2) only when medium speed (pin 3) or
low speed (pin4) are connected to black wire.
To Change Blower Speed:
(Belt Drive Drive Units)
1- Measure indoor blower wheel RPM.
2- Refer to unit nameplate to determine the blower motor
horsepower.
3- Referring to blower performance table in the front of this
manual, use the static pressure and RPM to determine
unit CFM.
4- The CFM can be adjusted at the motor pulley by adjusting
the pulley diameter.
Blower Belt Adjustment
Maximum life and wear can be obtained from belts only if prop-
er pulley alignment and belt tension are maintained.
Important-Tension new belt after a 24-48 hour period of op-
eration. This will allow belts to stretch and seat into
grooves. To increase belt tension, loosen two locking bolts
and pull mounting plate. Tighten motor mounting plate in
vertical position. See figure 11.
J38
Plug Wire Color
Lo-Lo Red
Med-Lo Yellow
Med-Med Blue