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NOTE:

The air conditioning relay disable jumper ACRDJ must

be disconnected to allow thermostat control of the outdoor unit
staging. (See Fig. 32.)

The thermostat closes the R to G-and-Y1 circuits for low-cooling
or closes the R to G-and-Y1-and-Y2 circuits for high-cooling. The
R to Y1 circuit starts the outdoor unit on low-cooling speed, and
the R to G-and-Y1 circuit starts the furnace blower motor BLWM
at low-cooling airflow which is the true on-board CF selection as
shown in Fig. 55. The R to Y1-and-Y2 circuits start the outdoor
unit on high-cooling speed, and the R to G-and-Y/Y2 circuits start
the furnace blower motor BLWM at high-cooling airflow. High-
cooling airflow is based on the A/C selection shown in Fig. 55.
The electronic air cleaner terminal EAC-1 is energized with 115
vac whenever the blower motor BLWM is operating.
When the thermostat is satisfied, the R to G-and-Y1 or R to
G-and-Y1-and-Y2 circuits are opened. The outdoor unit stops, and
the furnace blower BLWM and electronic air cleaner terminal
EAC-1 will remain energized for an additional 90 seconds. Jumper
Y1 to DHUM to reduce the cooling off-delay to 5 seconds. (See
Fig. 32.)

4. Thermidistat Mode

See Fig. 24-27 for thermostat connections
The dehumidification output, DHUM on the Thermidistat
should be connected to the furnace control thermostat terminal
DHUM. When there is a dehumidify demand, the DHUM
input is activated, which means 24 vac signal is removed from
the DHUM input terminal. In other words, the DHUM input
logic is reversed. The DHUM input is turned ON when no
dehumidify demand exists. Once 24 vac is detected by the
furnace control on the DHUM input, the furnace control
operates in Thermidistat mode. If the DHUM input is low for
more than 48 hours, the furnace control reverts back to

non-Thermidistat mode.
The cooling operation described in item 3. above also applies
to operation with a Thermidistat. The exceptions are listed
below:

a. Low cooling-When the R to G-and-Y1 circuit is closed and

there is a demand for dehumidification, the furnace blower
motor BLWM will drop the blower airflow to 86 percent of
low-cooling airflow which is the true on-board CF selec-
tion as shown in Fig. 55.

b. High cooling-When the R to G-and Y/Y2 circuit is closed

and there is a demand for dehumidification, the furnace
blower motor BLWM will drop the blower airflow to 86
percent of high-cooling airflow. High-cooling airflow is
based on the A/C selection shown in Fig. 55.

c. Cooling off-delay-When the

″

call for cooling

″

is satisfied

and there is a demand for dehumidification, the cooling
blower-off delay is decreased from 90 seconds to 5
seconds.

5. Super-Dehumidify Mode

Super-Dehumidify mode can only be entered if the furnace
control is in the Thermidistat mode and there is a demand for
dehumidification. The cooling operation described in item 3.
above also applies to operation with a Thermidistat. The
exceptions are listed below:

a. When the R to Y1 circuit is closed, R to G circuit is open,

and there is a demand for dehumidification, the furnace
blower motor BLWM will drop the blower airflow to 65
percent of low-cooling airflow for a maximum of 10
minutes each cooling cycle or until the R to G circuit closes
or the demand for dehumidification is satisfied. Low-
cooling airflow is the true on-board CF selection as shown
in Fig. 55.

Fig. 55—A/C or CF Airflow Selection Chart

Based on 350CFM/Ton

AIR CONDITIONING

AIRFLOW

070 MODEL

090 MODEL

110, 135,

TONS (12,000 BTU/HR)

(CFM)

& 155 MODELS

1-1/2

525