Application; Unit Components - Lennox CBX25UH Series Installation And Service Procedure

Application

All major blower coil components must be matched
according to Lennox recommendations for the unit to be
covered under warranty. Refer to the Product Specification
bulletin for approved system matchups. A misapplied system
will cause erratic operation and can result in early unit failure.
The units come with factory installed check and expansion
valve for all applications. The TXV valve has been installed
internally for a cleaner installation and is accessible if required.

Unit Components

CONTROL BOX
The CBX25UH control box is located above the blower
section shown in figure 2. Line voltage and electric heat
connections are made in the control box. Optional electric
heat fits through an opening located in the center of the
control box. When electric heat is not used, cover plates
cover the opening. The electric heat control arrangement is
detailed in the electric heat section of this manual.
TRANSFORMER
All CBX25UH series units use a single line voltage to
24VAC transformer mounted in the control box. The
transformer supplies power to the control circuits in the
indoor and outdoor unit. Transformers are rated at 40VA.
208/240VAC single phase transformers use two primary
voltage taps as shown in figure 3.
PRIMARY
ORANGE
240 VOLTS
RED
208 VOLTS
BLACK
Figure 3. 208/240 Volt Transformer
BLOWER RELAY
All CBX25UH units use a double-pole single-throw
(DPST) switch relay to energize the blower motor. The
relay coil is energized by blower demand from indoor
thermostat. When the coil is energized, a set of normally
open (N.O.) contacts closes to energize the blower motor on
cooling speed. When de-energized, a set of normally closed
(N.C.) contacts allows the electric heat relay to energize the
blower on heating speed (refer to unit wiring diagram).
TIME DELAY RELAY
Blower time delay operation:
1. When cooling demand is initiated, there is a 1 second
motor-on delay.
SECONDARY
BLUE
YELLOW
2. After the motor-on delay expires, motor ramps up to
100% and runs at 100% until cooling demand is
satisfied.
3. Once demand is met, motor runs at 100% for 45
seconds.
4. Motor ramps down to stop.
100%
2
1
CFM
1
SECOND
COOLING
DELAY
DEMAND
Figure 4. Blower Time Delay
BLOWER MOTOR (B3)
CBX25UH units use single-phase direct drive blower
motors with a run capacitor. Figure 5 shows the parts
arrangement. All motors have three speed taps. Typically,
the high speed tap is energized during normal operation.
All units are factory wired for heat pump and cooling
applications with or without electric heat. The unit wiring
diagrams will provide factory set blower speeds.
BLOWER ASSEMBLY
Figure 5. Blower Assembly
BLOWER MOTOR CAPACITOR
All CBX25UH series units use single-phase direct drive motors
with a run capacitor. The run capacitor is mounted on the
blower housing. See figure 5. Capacitor ratings are shown on
side of capacitor and indoor blower motor nameplate.
COIL
CBX25UH units have dual slab coils arranged in an A
configuration. Each coil has two or three rows of copper
tubes fitted with ripple-edged aluminum fins. An expansion
valve, feeds multiple parallel circuits through the coils. The coil
is designed to easily slide out of the unit cabinet.
PLASTIC DRAIN PANS
Drain pans are provided and installed on the CBX25UH,
The drain pans are made from fiberglass filled plastic.
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100%
CFM
OFF
45
SECS