Lennox CBX25UHV Series Installation And Service Procedure page 6

JUMPER SETTINGS
Table 1 lists the factory blower speed tap settings for
CBX25UHV series units. These settings are for nominal
tonnage match-ups with the CBX25UHV. When matched
with other sizes, it is recommended that the CFM be
adjusted to approximately 400 CFM per ton.
WARNING
Before changing jumper setting, make sure the
motor has completely stopped. Any jumper setting
change will not take place while the motor is running.
DANGER
Disconnect power from unit and wait at least five
minutes to allow capacitors to discharge before
attempting to adjust motor speed tap settings.
Failure to wait may cause personal injury or death.
Table 1. Factory Blower Speed Tap Settings
Speed Tap Selection
Cooling
Air Handler
Note 1
COOL
CBX25UHV­018
PIN #2
COOL
CBX25UHV­024
PIN #3
COOL
CBX25UHV­030
PIN #3
COOL
CBX25UHV­036
PIN #3
COOL
CBX25UHV­042
PIN #3
COOL
CBX25UHV­048
PIN #3-
COOL
CBX25UHV­060
PIN #3-
NOTES -
1. Condensing Unit
2. Heat Pump
3. Condensing Unit with electric heat only
4. Heat Pump with electric heat
* Minimum setting for heat
To change jumper positions, gently pull the jumper off the
pins and insert it onto the desired set of pins. Read the
Adjust Jumper, Cool Jumper, Heat Jumper and Delay
Jumper sections for details on the different jumper
selections available and conditions associated with each
one (figure 1 on page 5).
After the CFM for each application is determined, adjust the
jumper settings to reflect the CFM given in tables 2 through
8. Determine which table row of CFM volumes most closely
matches the desired CFM. Once a specific row has been
chosen (+, NORMAL, or -), CFM volumes from other rows
cannot be used.
Heating*
Note 2 Note 3 Note 4
COOL HEAT HEAT
PIN #2 PIN #2 PIN #2
COOL HEAT HEAT
PIN #3 PIN #2+ PIN #2+
COOL HEAT HEAT
PIN #3 PIN #2+ PIN #2+
COOL HEAT HEAT
PIN #3 PIN #2 PIN #2
COOL HEAT HEAT
PIN #3 PIN #2 PIN #2
COOL HEAT HEAT
PIN #3- PIN #2 PIN #2
COOL HEAT HEAT
PIN #3- PIN #2 PIN #2
ADJUST JUMPER
The ADJUST pins allow the motor to run at normal speed,
approximately 10% higher, or approximately 10% lower than
normal speed. Table 4 on page 7 lists three rows (+,
NORMAL, and -) with their respective CFM volumes. Notice
that the normal adjustment setting for heat speed position #3
is 1000 CFM. The + adjustment setting for that position is
1100 CFM and for the - adjustment setting is 895 CFM. After
the adjustment setting has been determined, choose the
remaining speed jumper settings from those offered in the
table in that row.
The TEST pin is available to bypass the BDC3 control and
run the motor at approximately 70%, to test that the motor is
operational. This is beneficial primarily in troubleshooting.
G terminal must be energized for motor to run.
COOL JUMPER
The COOL jumper is used to determine the CFM during a
cooling demand for either an air conditioner or a heat pump.
These jumper selections are activated for cooling when Y2
and DS terminals in the CBX25UHV are energized. They
are activated for heating when only Y2 is energized.
Applications without the Lennox ComfortSense
thermostat will provide 70% of the COOL CFM during
first-stage cooling for two-stage outdoor units. 100% of
COOL speed is provided for systems with a single-stage
outdoor unit.
Applications with the Lennox ComfortSense
thermostat, but no demand for de-humidification will
operate as follows: during a first-stage cooling call
(two-stage outdoor unit), the air volume is 70% of the COOL
jumper selection. This arrangement provides for additional
dehumidification during standard first-stage cooling. See
the tables that follow for various scenarios concerning use
of the ComfortSense
CBX25UHV series unit.
For applications with Harmony III
handler CFM volume is determined by the Harmony III
control center. The minimum blower speed is preset to 250
CFM for -018, -024, -030 and -036 units and 450 CFM for
-042, -048 and -060 units. This speed is not adjustable. See
notes in tables 4 and 5 on page 7.
With the thermostat set for Continuous Fan and without a
call for heating or cooling, the CBX25UHV provides 50% of
the COOL CFM selected.
NOTE - For two-stage heat pumps, the air handler operates
at 70% of the COOL selection until supplemental electric
heat is demanded. At that time, the air handler will operate
at the selected HEAT speed. This arrangement provides
warmer supply air during second-stage heating.
Page 6
®
®
7000 thermostat and the
®
zone control, the air
®
7000
7000