Model Number Identification; Adjusting The Bdc3 Blower Control; Adjusting The Blower Speed - Lennox CBA25UHV-018 Unit Information

Model Number Identification

Unit Type
CB = Air Handler
Refrigerant Type
A = Aluminum Coil/R-410A

Adjusting the BDC3 Blower Control

WARNING
Electrostatic discharge can affect
electronic components. Take care
during unit installation and service to
protect the unit's electronic controls.
ELECTROSTATIC
Precautions will help to avoid control
DISCHARGE
exposure to electrostatic discharge
(ESD)
by putting the unit, the control and the
Precautions and
technician at the same electrostatic
Procedures
potential. Touch hand and all tools
on an unpainted unit surface before
performing any service procedure to
neutralize electrostatic charge.
JP1 15 PIN
PLUG (BOARD
TO MOTOR)
QC1
24V ACCESSORY
SERVICE
CONTACTS –
RATED FOR 1 AMP 24V/1A
OR LESS
QC2
NOR
M
+
OPERATIONAL
-
SELECTOR PINS
TES
(AFFECTS BOTH
HEATING AND T
ADJUST
COOLING MODES)
HEATING SPEED
SELECTOR PINS
COOLING SPEED
SELECTOR PINS
FIGURE 1. BDC3 Variable Speed Control Selections
CB A 25 UH V - 030 - 230 - 10
Series
Blower Motor
V = Variable Speed
JP1
4 4 4
3 3 3
2 2 2
1 1 1
HEAT COOL DELAY CFM RUN
DIAGNOSTIC
LEDS
FAN DELAY
SELECTOR PINS
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
Merit CBA25UHV units are equipped with a vari-
®
able-speed motor that is capable of maintaining a spec-
ified CFM throughout the external static range. A particu-
lar CFM can be obtained by positioning jumpers (COOL,
HEAT, and ADJUST) on the BDC3 control.
The jumpers are labeled 1, 2, 3, and 4. This indicates
the selected air volume (CFM). The ADJUST jumper is
labeled Test, -, +, and Norm. The - and + pin settings are
used to add or subtract a percentage of the CFM select-
ed. The Test jumper is used to operate the motor in the
test mode. The delay jumper controls the timing pattern in
which the fan delay occurs.
Figure 1 illustrates the BDC3 control. Use tables on pages
5 and 6 to determine the correct air volume for heat and
cool speed taps.
Diagnostic LEDs located on the BDC3 control to assist in
servicing the unit. Read the jumper settings section before
adjusting blower speed. Refer to page 5 for identification
and information.

Adjusting the Blower Speed

Diagnostic LEDs
1 - RUN LED indicates there is a demand for the blower
motor to run.
2 - CFM LED indicates the cubic feet per minute at
which the unit is operating. The light flashes once
for approximately every 100 CFM. For example, if
the unit is operating at 1000 CFM, CFM LED will
flash 10 times. If the CFM is 1150, CFM LED will
flash 11 full times plus one fast or half flash.
At times, the light may appear to flicker or glow. This is
normal and occurs when the control is communicating
with the motor between cycles.
Move the jumper pins to select the blower speed needed
to meet application CFM requirements.
Page 4
Minor Revision Number
Voltage
230 = 208/230V-1 phase-60hz