Lennox ML193UH045P36B Unit Information page 18

1 - Remove thermostat demand and allow unit to cycle
off.
2 - Install a tee in the negative (-) line (red tubing) and a
tee in the positive (+) line (black tubing) running
from the pressure switch to the cold end header
box.
3 - Install a manometer with hose from the negative (-)
side of the manometer to the tee installed in the
negative (-) line and with hose from the positive (+)
side of the manometer to the tee in the positive (+)
line.
NOTE - Both sides of the cold end header box are nega­
tive. However the (+) port reads less negative pressure
than the (-) port.
C- Blower Compartment
Blower motor (B3) and capacitor (C4), are located in the
blower compartment. The blower compartment can be ac­
cessed by removing the blower access panel.
Blower Motor Housing
BOLTS
CAPACITOR
To Remove Blower From Unit: Disconnect Power, Remove Control
Box, Remove Bolts and Unplug Motor Wires From Control. Then
Slide Out Front of Unit.
FIGURE 17
Measuring Pressure Differential
4 - Operate unit and observe manometer reading.
5 - Remove thermostat demand and allow to cycle off.
6 - Remove manometer and tee's. Reinstall combus­
FIGURE 16
1. Blower Motor (B3) and Capacitor (C4)
All ML193UH units use single-phase direct-drive blower
motors. All motors are 120V permanent split capacitor mo­
tors to ensure maximum efficiency. See SPECIFI­
CATIONS table at the front of this manual for more detail.
See motor nameplate for capacitor ratings.
MOTOR
Page 18
RED TUBING
NEGATIVE
BLACK TUBING
POSITIVE
Readings will change as heat exchanger warms.
a. Take one reading immediately after start‐up.
b. Take a second reading after unit has reached
steady state (approximately 5 minutes). This will be
the pressure differential.
The pressure differential should be greater
than those listed in table 10.
tion air sensing hoses to the pressure switch.