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CBA27UHE units are equipped with an indoor blower motor
that is permanent magnetic with constant torque. The motor
has 5 signal level speed taps, all referenced to the same sig
nal common. Each tap requires 24 volts to energize.
Multiple Taps Energized
It is acceptable to have more than one tap energized at once
but the micro-controller (integrated in the motor) will default
to the highest tap. For example tap five will have precedence
over tap four.
Input Voltage Requirements
The circuit is designed to be operated with AC voltage. To
enable a tap requires 12 to 33VAC. Expected current draw
will be less than 20mA.
Troubleshooting
Troubleshooting the motor is an easy process. Follow steps
below.
1- Shut off power to unit.
2- Remove input plug from motor. Turn power back on
to unit.
3- Check for 230 volts across terminals “L” and “N” on
the input plug. See figure 4. If voltage is present con
tinue. If voltage is not present problem may be may
be up stream of the motor input plug.
4- Check for 24 volts across terminals “C” and speed
tap used (1, 2, 3, 4 or 5) on the input plug. See figure
4. If 24 volts is not present problem may be up stream
of the motor input plug.
If correct voltage is present in steps 3 and 4 and motor is not
operating properly, replace motor. The motor is not field re
pairable.
H-Coil
CBA27UHE units have dual slab coils arranged in an “A”
configuration. Each coil has two or three rows of aluminum
tubes fitted with ripple-edged aluminum fins. An expansion
valve complete with screen, feeds multiple parallel circuits
through the coils. The coil is designed to easily slide out of the
unit cabinet.
I-Condensate Drain Pans
Both upflow/downflow and horizontal drain pans are pro
vided and installed on the CBA27UHE units. The drain pans
are made from fiberglass filled plastic. The drain hole on
horizontal pans are used for right‐hand discharge only, and
must be plugged when the unit is configured for left‐hand
discharge.
III-OPTIONAL ECB29 ELECTRIC HEAT
A-Matchups and Ratings
The Electric Heat Data on pages 15-25 show all approved
CBA27UHE to ECB29 matchups and electrical ratings.
B-Electric Heat Components
ECB29 parts arrangement is shown in figures 5 through 10. All
electric heat sections consist of components mounted to the
electric heat vestibule panel and electric heating elements ex
posed directly to the air stream. 208/230V electric heat sec
tions may be equipped with circuit breakers. The circuit
breakers are designated by CB in the model number. The
electric heat section is connected to the unit via jack J2,
which plugs into plug P2 of the unit.
Electric Heat Sequencer Relays
(K32, K33, K34, K35, K116, K117) (208/230 volt only)
Relays K32, K33, K34, K35, K116 and K117 are N.O.
sequencer relays with a resistive element for a coil
and a bi‐metal disk which actuates the contacts. The
relays are located on the electric heat vestibule panel and
are energized by a 24V heating demand (W1, W2, and
W3) via jack/plug 2. When energized, the internal resist
ance heats the bi‐metal disk causing the contacts to close.
When the relay is de‐energized, the disk cools and the
contacts open. The relays energize different stages
of heat, as well as the blower. The blower is always
first on and last off.
Primary(S15) & Secondary(S20) Temperature Limits
Both the primary (S15) and secondary (S20) limits are lo
cated on the electric heat vestibule panel and are exposed
directly to the air stream through an opening in the panel.
The high temperature limits are SPST N.C. limits with the
primary limit being an auto‐reset limit and the secondary
limit being a “one‐time” limit. One‐time limits need to be re
placed when opened. The limits are factory set and are not
adjustable.
208/230 Volt Electric Heat Sections
Each stage of the 208/230 electric heat is protected
by a primary (S15) and secondary (S20) high temper
ature limit. Both S15 and S20 are located in the same
housing. Each stage use the same style of limits. Both the
primary and secondary limits are wired in series with a
heat element. When either S15 or S20 opens, the corre
sponding heat element is de‐energized. All other
heating elements remain energized. The primary high
temperature limit opens at 150
_
F + 5
_
F (65.5
_
C + 2.8
_
C)
on a temperature rise and automatically resets at
110
_
F + 9
_
F (43.3
_
C + 5.0
_
C) on a temperature fall.
The secondary high temperature limit opens at
333
_
F + 10
_
F (167.2
_
C + 5.6
_
C) on a temperature
rise. If the secondary limit opens it will need to be re
placed.
