Lennox CBA25UH Series - Page 7

Page 7
UPFLOW DRAIN PAN
EXPANSION VALVE
COIL
BLOWER COMPARTMENT
CONTROL BOX
ELECTRIC HEAT
FIGURE 2. Typical Unit Parts Arrangement
Application
All major blower coil components must be matched ac-
cording to Lennox recommendations for the unit to be
covered under warranty. Refer to the Product Specica-
tion 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 expan-
sion valve for all applications. The TXV valve has been
installed internally for a cleaner installation and is acces-
sible if required.
Unit Components
CONTROL BOX
The CBA25UH control box is located above the blower
section shown in gure 2. Line voltage and electric heat
connections are made in the control box. Optional electric
heat ts 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 CBA25UH 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 gure 3.
BLUE
YELLOW
ORANGE
RED
BLACK
240 VOLTS
208 VOLTS
PRIMARY
SECONDARY
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 cool-
ing 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.
2 - After the motor-on delay expires, motor ramps up
to 100% and runs at 100% until cooling demand is
satised.
3 - Once demand is met, motor runs at 100% for 45
seconds.
4 - Motor ramps down to stop.
1
SECOND
DELAY
OFF
100%
CFM
100%
CFM
45
SECS
COOLING
DEMAND
1
2
34
FIGURE 4. Blower Time Delay
BLOWER MOTOR (B3)
CBA25UH -018, -024, -030, -036 and -048 units use sin-
gle-phase direct drive blower motors with a run capacitor.
Figure 5 shows the parts arrangement. All motors have
three speed taps. Typically, the MED speed tap is ener-
gized during normal operation.
All units are factory wired for heat pump and cooling ap-
plications with or without electric heat. The unit wiring dia-
grams will provide factory set blower speeds.