Lennox CB29M-21, Unit Information

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Page 32
VI–TYPICAL OPERATING CHARACTERISTICS
A–Blower Operation and Adjustment
NOTE– The following is a generalized procedure
and does not apply to all thermostat controls.
1– Blower operation is dependent on thermostat
control system.
2– Generally, blower operation is set at thermostat
subbase fan switch. With fan switch in ON position,
blower operates continuously. With fan switch in
AUTO position, blower cycles with demand.
3– In all cases, blower and entire unit will be off when
the system switch is in OFF position.
B–External Static Pressure
1– Measure tap locations as shown in figure 23.
FIGURE 23
STATIC PRESSURE TEST
MANOMETER
SUPPLY
RETURN
UNIT SHOWN IN
UPFLOW POSITION
2– Punch a 1/4” (6mm) diameter hole in supply and re-
turn air plenums. Insert manometer hose flush with
inside edge of hole or insulation. Seal around the
hose with permagum. Connect the zero end of the
manometer to the discharge (supply) side of the sys-
tem. On ducted systems, connect the other end of
manometer to the return duct as above. For systems
with non–ducted returns, leave the other end of the
manometer open to the atmosphere.
3– With only the blower motor running and the
evaporator coil dry, observe the manometer
reading. Adjust blower motor speed to deliver
the air desired according to the job requirements.
4– External static pressure drop must not exceed
0.5” W.C. (1.2 kPa)
5– Seal around the hole when the check is complete.
C–Blower Speed Taps
Blower speed tap selection is accomplished by
changing the taps at the blower motor harness con-
nector. Disconnect harness connector from motor to
expose speed selectors. Blower speed selections are
listed in table 14. Refer to the ECB29 installation
instructions for minimum allowable blower speed,
when using electric heat.
To Change Blower Speed
1– Turn off electric power to furnace.
2– Remove blower access door.
3– Disconnect blower motor harness from motor.
4– Select desired speeds for heating and cooling.
(Black = cooling high speed, Orange = common,
Yellow = electric heat only).
TABLE 14
BLOWER SPEED SELECTION
MOTOR
TWO
SPEED
THREE
SPEED FIVE
SPEED
SPEED
SPEED
MOTOR
SPEED
MOTOR
SPEED
MOTOR
Common 1 1 1
High 2 2 2
Medium High ––– ––– 3
Medium ––– 3 4
Medium Low ––– ––– 5
Low 3 4 6
NOTE– The table does not apply to 460 volt units.
5– Depress harness connector tab to release wire
terminal. Select connector location for new
speed (refer to unit wiring diagram). Insert wire
terminal until it is securely in place. See figure 24.
6– Replace harness connector to motor .
FIGURE 24
BLOWER SPEED TAP SELECTION
HARNESS
CONNECTOR
MOTOR
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.