Lennox CBX25UH Series Manual

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©2018 Lennox Industries Inc.
CBX25UH (-10)
Service Literature
Corp. 1504-L6
September 2018
INSTALLATION AND SERVICE PROCEDURE
CBX25UH (-10) Series
WARNING
Improper installation, adjustment, alteration, service or
maintenance can cause personal injury, loss of life, or
damage to property.
Installation and service must be performed by a licensed
professional installer (or equivalent) or a service agency.
CAUTION
As with any mechanical equipment, contact with sharp
sheet metal edges can result in personal injury. Take care
while handling this equipment and wear gloves and pro
tective clothing.
IMPORTANT
The Clean Air Act of 1990 bans the intentional venting of
refrigerant (CFCs, HCFCs and HFCs) as of July 1, 1992.
Approved methods of recovery, recycling or reclaiming
must be followed. Fines and/or incarceration may be
levied for noncompliance.
Table of Contents
Unit Dimensions 2............................
Specifications / Electrical Data 3................
Model Number Information 4...................
Blower Data 4................................
Application 6.................................
Unit Components 6............................
Optional ECB25 Electric Heat 7.................
Configuration Modification 10...................
Electrical Connections 16......................
Wiring Diagrams 18...........................
Start-Up Operations 20........................
Sequence of Operations 21....................
Performance Checklists 22.....................
The CBX25UH units are high-efficiency air handlers. Several
models are available in sizes ranging from 1‐1/2 through
5-tons. The CBX25UH is designed for HFC-410A refrigerant.
CBX25UH series units are designed to be matched with either
a 13 SEER air conditioner or heat pump, but can be matched
with other air conditioners or heat pumps as noted in the rating
information. See Product Specification bulletin.
This air handler is designed for indoor installation only. As
shipped, the unit is ready for installation in either upflow or
horizontal left-hand. Field modifications are required for
right-hand air discharge applications. Electric heat, down
flow air discharge application kits, air filters and other
various accessories are available and listed in the
CBX25UH Product Specification bulletin for ordering.
All units come with a factory installed check/expansion
valve.
Information contained in this manual is intended for use by
experienced licensed HVAC service technicians only. All
specifications are subject to change. Procedures outlined in
this manual are presented as a recommendation only and do
not supersede or replace local or state codes.

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CBX25UH Unit Dimensions – Upflow – inches (mm)
NOTE - Unit is shipped configured for horizontal left-hand air discharge. Unit may be converted to horizontal
right-hand air discharge by repositioning horizontal drain pan.
Dimensions remain the same in all configurations.
52-1/2 1334

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Specification and Electrical Data
SPECIFICATION
General
Data
Model Number CBX25UH018 CBX25UH024 CBX25UH030 CBX25UH036
Nominal tonnage 1.5 2 2.5 3
Connections Suction/Vapor line (o.d.)  in. sweat 3/4 3/4 3/4 7/8
Liquid line (o.d.)  in. sweat 3/8 3/8 3/8 3/8
Condensate  in. fpt (2) 3/4 (2) 3/4 (2) 3/4 (2) 3/4
Indoor
Coil
Net face area  ft.23.11 3.56 4.00 4.89
Tube outside diameter  in. 3/8 3/8 3/8 3/8
Number of rows 3 3 3 3
Fins per inch 14 14 14 14
Blower Wheel nominal diameter x width  in. 9 x 6 9 x 6 10 x 8 10 x 8
Blower motor output  hp 1/3 1/3 1/3 1/3
1Filters Size of filter  in. 12 x 20 x 1 15 x 20 x 1 15 x 20 x 1 18 x 20 x 1
Shipping Data 1 package  lbs. 109 127 133 163
ELECTRICAL DATA
Voltage  1 phase (60 hz) 208/240V 208/240V 208/240V 208/240V
2Maximum over-current protection (unit only) 15 15 15 15
3Minimum circuit ampacity (unit only) 2.0 2.0 2.4 2.5
Blower Motor Full Load Amps 1.6 1.6 1.9 2.0
SPECIFICATIONS
General
Data
Model Number CBX25UH042 CBX25UH048 CBX25UH060
Nominal tonnage 3.5 4 5
Connections Suction/Vapor line (o.d.)  in. sweat 7/8 7/8 7/8
Liquid line (o.d.)  in. sweat 3/8 3/8 3/8
Condensate  in. fpt (2) 3/4 (2) 3/4 (2) 3/4
Indoor
Coil
Net face area  ft.25.83 7.00 7.00
Tube outside diameter  in. 3/8 3/8 3/8
Number of rows 3 3 3
Fins per inch 14 14 14
Blower Wheel nominal diameter x width  in. 12 x 8 11 x 9 12 x 9
Blower motor output  hp 1/3 1/2 1/2
1Filters Size of filter  in. 18 x 24 x 1 18 x 24 x 1 18 x 24 x 1
Shipping Data 1 package  lbs. 168 186 186
ELECTRICAL DATA
Voltage  1 phase (60 hz) 208/240V 208/240V 208/240V
2Maximum overcurrent protection (unit only) 15 15 15
3Minimum circuit ampacity (unit only) 2.4 4.9 4.9
Blower Motor Full Load Amps 1.9 3.9 3.9
1Disposable filter.
2HACR type circuit breaker or fuse.
3Refer to National or Canadian Electrical Code manual to determine wire, fuse and disconnect size requirements. Use wires suitable for at least 167°F.

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Model Number Identification
Unit Type
CB - Air Handler
Series Nominal Cooling Capacity
018 = 1.5 tons
024 = 2 tons
030 = 2.5 tons
036 = 3 tons
042 = 3.5 tons
048 = 4 tons
060 = 5 tons
Configuration
UH = Up-Flow / Horizontal
CB X 25 UH − 030 − 230 − 10
Refrigerant Type
X = HFC-410A
Minor Revision Number
Voltage
230 = 208/230V-1 phase-60hz
Blower Data
The cooling blower speed is factory configured to provide
correct airflow for an outdoor unit that matches the cooling
capacity rating of the air handler.
CHANGE BLOWER SPEED
If the outdoor unit is smaller than the maximum cooling
capacity rating for the air handler, the cooling blower speed
may need to be changed. Refer to blower performance
chart, table 1 on page 5. Use figure 1 on page 4 as a
illustrated guide to the following procedure:
1. Disconnect all power supplies.
2. Remove the air handler access panel.
3. A blower relay harness is used to connect blower relay
terminals 2and 5. The third connector is mated to the
BLUE (MED) wire.
4. Disconnect the BLUE (MED) wire connection.
5. Determine the required blower speed and connect
either the blower lead RED (LO) or BLACK (HI) to
the blower relay harness.
NOTE — Reuse the factory-installed plastic cap on the
connector that is not used.
6. Replace all panels.
7. Reconnect power.
CAUTION
Electrostatic discharge can affect electronic compo
nents. Take precautions during unit installation and
service to protect the unit's electronic controls. Pre
cautions will help to avoid control exposure to electro
static discharge by putting the unit, the control and
the technician at the same electrostatic potential.
Neutralize electrostatic charge by touching hand and
all tools on an unpainted unit surface before perform
ing any service procedure.
2
BLUE (MED) RED (L0)
BLACK (HI)
YELLOW (COM)
5BLOWER RELAY
BLOWER RELAY
PLASTIC CAPS
4-PIN
BLOWER CONNECTOR
HARNESS
Figure 1. Changing Blower Speed
NOTE — Refer to wiring diagram located on the unit access panel (or figure 1 above) and blower performance (table 1).
SAll air data measured external to unit with 1 inch non-pleated air filter in place.
SAll factory settings are medium speed except the -48 which is set to low speed from the factory.
SAll data given while air handler is operating with a dry DX coil.

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Table 1. Blower Performance (3-Speed PSC) - 240V (CFM @ ESP. - in. W. C.)
Air Handler
Model Blower Speed .10" WC .20" WC .30" WC .40" WC .50" WC
18
Low (Red)
Med (Blue)
High (Black)
510
670
905
495
650
865
475
630
820
420
595
770
325
505
705
24
Low (Red)
Med (Blue)
High (Black)
630
885
1130
625
875
1100
615
850
1070
610
820
1010
580
780
950
30
Low (Red)
Med (Blue)
High (Black)
900
1075
1240
865
1060
1210
830
1030
1170
780
985
1135
740
940
1085
36
Low (Red)
Med (Blue)
High (Black)
1075
1300
1510
1040
1250
1450
1000
1205
1390
950
1145
1320
900
1085
1245
42
Low (Red)
Med (Blue)
High (Black)
1325
1490
1820
1315
1465
1770
1300
1440
1690
1275
1395
1600
1225
1315
1500
48
Low (Red)
Med (Blue)
High (Black)
1775
1995
2070
1710
1895
1970
1645
1800
1850
1565
1685
1719
1470
1560
1595
60
Low (Red)
Med (Blue)
High (Black)
1675
1965
2140
1630
1925
2085
1580
1875
2000
1520
1800
1895
1450
1695
1795
NOTE — Refer to wiring diagram located on the unit access panel and blower performance (table 1).
SAll air data measured external to unit with 1 inch
non-pleated air filter in place.
SAll factory settings are medium speed except the -48
which is set to low speed from the factory.
SAll data given while air handler is operating with a dry
DX coil.
SBlower Performance (CFM vs. ESP inches H2O)
SCooling speeds should not be reduced below factory
setting.
SUnits with electric heat approved at 0.5” maximum and
medium blower speed minimum.
ELECTRIC HEAT SECTION
(PLATE TO BE REMOVED IF
INSTALLED)
CONTROL BOX
BLOWER COMPARTMENT
COIL
HORIZONTAL DRAIN PAN
EXPANSION VALVE (R-22
OR R-410A)
UP-FLOW DRAIN PAN
Figure 2. Unit Parts Arrangement

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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.
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
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.
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.
1
SECOND
DELAY
OFF
100%
CFM 100%
CFM
45
SECS
COOLING
DEMAND
12
34
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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Optional ECB25 Electric Heat
The electric heat sections provide field installed electric
heat for air handler units.
Table 2 shows the available heat sections. Refer to the
Product Specifications for heat section applications.
Table 2. Electric Heat Sections
Termination Type Part Number Catalog
Number
2.5kW with stripped wires 0668142-10 89W42
5 kW with terminal block 0668142-02 89W43
5 kW with breaker 0668142-03 89W44
7.5 kW with breaker 0668142-04 89W45
7.5 kW with terminal block 0668142-05 89W46
10 kW with terminal block 0668142-06 89W47
10 kW with breaker 0668142-07 89W48
12.5 kW with breaker 0668142-11 89W49
15 kW with breaker 0668142-08 89W50
20 kW with breaker 0668142-09 89W51
HEAT SECTION INSTALLATION
Be sure to disconnect all power to the unit while you install
and service this equipment. Use proper tools and
protective equipment during installation and service.
Before installing the unit, check information on the unit
rating plate to ensure that the unit meets the job
specification, proper electrical power is available, and that
proper duct clearances are maintained.
WARNING
Before installing or servicing unit, be sure ALL power to
the unit is OFF. More than one disconnect switch may be
present. Electrical shock can cause personal injury or
death!
NOTE - If installing heat sections at the same time as the air
handler unit, install the electric heat section in the air
handler unit before setting the air handler unit and attaching
the plenum.
1. Shut off all power to the air handler unit. More than one
disconnect may be required.
2. Remove air handler access panel and keep the 6
screws to reattach access panel after installing heat
elements.
3. Disconnect any existing field supply wires and pull
them out of the air handler. Disconnect and remove
wiring harness and fastener (see figure 6). If not
removed, these items will prevent the heat section’s
base from resting properly in the compartment.
4. Remove the no-heat seal plate in the air handler frame.
See figure 6.
Figure 6. Prepare to Install Heat Element
NO‐HEAT
SEAL PLATE REMOVE SCREWS;
THEN REMOVE
NO-HEAT SEAL
PLATE
SEPARATE CONNECTOR;
DISCARD WIRE HARNESS
WIRE
HARNESS
OFFSET
REMOVE FASTENER SECURING WIRES
IF PRESENT
5. Slide the electric heat section into the air handler. Be
careful that the heating elements do not rub against the
sheet metal opening when they slide into the air
handler. The side opposite the side with the mounting
holes should slip behind the offset. The mounting holes
should then line up with holes in the air handler control
box.
6. Secure the electric heater assembly into place with the
screws that were removed from the heat element
panel. Install two field-provided #8 SDST screws in the
front of the electric heater assembly (see figure 7).
INSTALL SCREWS
REMOVED FROM
THE NO-HEAT
SEAL PLATE.
INSTALL 2 FIELD-PROVIDED SCREWS TO SECURE THE
FRONT OF THE HEATER CIRCUIT BREAKER ASSEMBLY TO
THE FRONT FLANGE OF THE AIR HANDLER.
Figure 7. Installing the Heat Element Assembly

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7. The air handler access panels have knockouts over the
circuit breaker opening. Knock out both plates to
accommodate the circuit breaker levers. If installing a
heat element assembly with circuit breakers, remove
the knockouts but do not install the access panel until
all electrical connections have been completed.
IMPORTANT - To remove knockouts, knock them out in the
same direction the punch did. Always start with the smallest
knockout and work outward to the knockout for the
appropriately-sized hole.
WARNING
Foil face insulation must be cut to eliminate the possibility
for any frayed foil to coming in contact with any main or
low voltage connections. Insulation must be kept a
minimum of 1/2” away from any electrical connection.
CHANGING CIRCUIT BREAKER ORIENTATION
The air handler comes from the factory setup for horizontal
left-hand discharge which will require no change in the
circuit breaker orientation. However, if the air handler is
installed in a horizontal right-hand discharge position, the
breaker will need to be rotated 180º so that the UP position
of the breaker is the ON position. The circuit breaker
orientation change is required by UL 1995, Article 26.18 (25
September 2005).
1. The factory default configuration for the two circuit
breakers is horizontal left-hand discharge which will
require no change (see figure 9). To change the
applicable circuit breakers orientation for right-hand
discharge, proceed to step 2.
2. Locate the one clip which is located on the right side
(see arrow) of each breaker (see figure 8). The clip
secures the circuit breaker to the mounting bracket.
Pull the clip to release the breaker from the mounting
bracket.
CLIP
BREAKER(S)
MOUNTING
BRACKET
NOTE - There may be only one clip securing
each circuit breaker.
CIRCUIT
BREAKER
Figure 8. Circuit Breaker Clip
UPFLOW AND HORIZONTAL
LEFT (FACTORY DEFAULT) HORIZONTAL RIGHT
Figure 9. Circuit Breaker Orientation

Page 9
3. Flip the breaker so that the wires attached to the circuit
breakers terminals are on the left side (see figure 9).
4. Use the black clip to reattach the circuit breaker to the
mounting bracket.
CIRCUIT BREAKERS
AIR HANDLER ACCESS PANEL
CIRCUIT BREAKERS
KNOCKOUTS
Figure 10. Circuit Breaker Knockouts
BREAKER ELECTRICAL CONNECTIONS
WARNING
Electric shock hazard! - Disconnect all
power supplies before servicing.
Replace all parts and panels before op
erating.
Failure to do so can result in death or elec
trical shock.
WARNING
USE COPPER CONDUCTORS ONLY.
NOTE - Refer to the nameplate on the air handler unit for
minimum circuit ampacity and maximum overcurrent
protection size.
The air handler units are provided with openings to be used
with 1-1/2 inch trade size (1-31/32 inch diameter) conduit.
If you want a single point power supply, refer to the
nameplate on the single point power supply accessory for
minimum circuit ampacity and maximum overcurrent
protection size. Select the proper supply circuit conductors
in accordance with tables 310-16 and 310-17 in the
National Electric Code, ANSI/NFPA No. 70 or tables 1
through 4 in the Canadian Electric Code, Part I, CSA
Standard C22.1.
Refer to figure 28 for typical low voltage field wiring for air
handler/condensing unit and heat pump applications.
Figure 29 is a diagram of the air handler connections and
the heater elements high-voltage wiring.
1. Make wiring connections as follows -
Heaters equipped with circuit breakers—Connect
field power supply wiring to circuit breaker(s). Figure 11
shows L1, L2 and ground GND connections for a
2-breaker configuration.
ON
OFF
60
ON
OFF
60
Figure 11. Field Power Supply Wiring
L1
L2
CIRCUIT 1
L1
L2
CIRCUIT 2
GND 208/240 VOLT FIELD
SUPPLY WIRES
Field Supply
Ground Wires
Heaters equipped with terminal blocks—Connect
field power supply wiring to terminal block(s).Figure 12
shows L1, L2 and ground (GND) connection for a
terminal block configuration.
Figure 12. Terminal Block Connections
L1
L2
GND
208/240 VOLT FIELD
SUPPLY WIRES
FIELD SUPPLY
GROUND WIRES
2. Remove the interface harness from the air handler unit
and connect the 6-pin connector on the heater
assembly to the mating connector on the air handler
unit.
3. For applications using a two‐stage room thermostat
and/or an outdoor thermostat, connect wiring as shown
in figure 28.

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CIRCUIT BREAKER COVER INSTALLATION
1. Remove any installed patch plates still present .
2. Remove paper covering adhesive back around
backside perimeter of circuit breaker cover (figure 13).
3. Position the breaker cover over the air handler circuit
breaker opening (figure 14).
CIRCUIT BREAKER COVER
(BACKSIDE)
REMOVE PAPER COVERING
STICK BACK
Figure 13. Remove Paper Cover
IMPORTANT
Confirm air tight seal between breaker cover and air
handler access panel. Apply a thin silicone bead to the
adhesive back seat to ensure air tight seal.
Failure to seal circuit breaker cover will allow warm moist
air to be pulled into control panel which can create
condensation to form on the circuit breaker and other
electrical components within the control panel.
Figure 14. Typical Circuit Breaker Cover Installation
AIR HANDLER SPEED CONNECTIONS
When using the electric heat sections with air handler units,
you must adjust the air handler speed according to the size of
electric heat and air handler unit. Air handler speed tap for
electric heat in upflow and horizontal position is medium.
For downflow it is high speed. See specific air handler
installation instructions for air handler speed adjustment
procedure and location.
1. Set the thermostat above room temperature.
2. Check the heat pump and the heat section for normal
operation.
3. Set the thermostat to desired setting.
4. Affix the wiring diagram sticker to air handler scroll,
aligned with circuit breaker unit wiring diagram sticker.
Configuration Modification
UPFLOW APPLICATION
1. The air handler must be supported on the bottom only
and set on solid floor or field‐supplied support frame.
Securely attach the air handler to the floor or support
frame.
2. If installing a unit in an upflow application, remove the
horizontal drain pan. IMPORTANT - The horizontal
drain pan is not required in upflow air discharge
installations; its removal provides the best
efficiency and air flow.
3. Place the unit in the desired location and slope unit as
previously mentioned. Connect return and supply air
plenums as required using sheet metal screws.
4. Install units that have no return air plenum on a stand
that is at least 14” from the floor. This will allow proper
air return.
HORIZONTAL DRAIN PAN
IMPORTANT! REMOVE PAN
FOR BEST EFFICIENCY
AND AIR FLOW.
UPFLOW
DRAIN PAN
UPFLOW DRAIN CON
NECTIONS (BOTH
SIDES; USE ONE SIDE
OR OTHER)
HORIZONTAL DRAIN
CONNECTIONS
(BOTH SIDES; NOT
USED)
Figure 15. Upflow Configuration