Lennox CBX25UHV-018 Installation Instructions Manual Download Page 18

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speed position #4 is 1000 CFM. The + adjustment setting for
that position is 1080 CFM and for the - adjustment setting is
910 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 must be energized for motor to run.

COOL JUMPER

The

COOL

jumper is used to determine the CFM during

either cooling or heat pump operation without a call for
electric heat. These jumper selections are activated for
cooling when Y2 and DS terminals in the Merit

CBX25UHV are energized. The are activated for heating
when Y2 is energized.

Applications

without

the Lennox ComfortSense

7000

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

7000

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

7000 thermostat

and the Merit

CBX25UHV series unit.

For applications with Harmony III

zone control, the air

handler CFM volume is determined by the Harmony III
control center. The minimum blower speed is
predetermined at 250 CFM for -018, -024, -030 and -036
units and 450 CFM for -042, -048 and -060 units. This
speed is not adjustable. See footnotes in the blower
performance tables.

With the thermostat set for

Continuous Fan

and without a

call for heating or cooling, the Merit

CBX25UHV provides

50% of the

COOL

CFM selected.

NOTE

- For two-stage heat pumps, air handler will operate

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.

Table 3. Merit

CBX25UHV‐018 Air Handler Performance (0 through 0.80 in. w.g. [0 — 200 Pa] External Static Pressure Range)

“ADJUST”

Jumper

Setting

Jumper Speed Positions

“HEAT” Speed

First-Stage “COOL” Speed

Second-Stage “COOL” Speed

cfm

470

670

890

1080

350

470

620

760

470

675

890

1090

NORM

440

615

810

1000

350

450

560

700

435

610

815

1020

–

400

560

730

910

350

420

520

650

400

575

725

915

NOTES
The effect of static pressure, filter and electric heater resistance is included in the air volumes listed.
First-stage cooling air volume is 70% of COOL (second-stage) speed setting. Continuous blower speed is approximately 50% of COOL speed setting.
Lennox Harmony III™ Zoning System applications minimum blower speed is 250 cfm.

Table 4. Merit

CBX25UHV‐024 Air Handler Performance (0 through 0.80 in. w.g. [0 — 200 Pa] External Static Pressure Range)

“ADJUST”

Jumper

Setting

Jumper Speed Positions

“HEAT” Speed

First-Stage “COOL” Speed

Second-Stage “COOL” Speed