Thermidistat Mode; Super-Dehumidify Mode; Continuous Blower Mode - Carrier 58MVP Installation, Start-Up, And Operating Instructions Manual

The furnace control CPU can start up the cooling unit in either
low- or high-cooling. If starting up in low-cooling, the furnace
control CPU determines the low-cooling on-time (from 0 to 20
minutes) which is permitted before switching to high-cooling.
If the power is interrupted, the stored history is erased and the
furnace control CPU will select low-cooling for up to 20
minutes and then energize the air conditioning relay ACR to
energize the Y/Y2 terminal and switch the outdoor unit to
high-cooling, as long as the thermostat continues to call for
cooling. Subsequent selection is based on stored history of the
thermostat cycle times.
The wall thermostat "calls for cooling", closing the R to
G-and-Y circuits. The R to Y1 circuit starts the outdoor unit
on low-cooling speed, and the R to G-and-Y1 circuits starts
the furnace blower motor BLWM at low-cooling airflow
which is the true on-board CF selection as shown in Fig. 35.
If the furnace control CPU switches from low-cooling to
high-cooling, the furnace control CPU will energize the air
conditioning relay ACR. When the air conditioning relay ACR
is energized the R to Y1-and-Y2 circuits switch the outdoor
unit to high-cooling speed, and the R to G-and-Y1-and-Y/Y2
circuits transition the furnace blower motor BLWM to high-
cooling airflow. High-cooling airflow is based on the A/C
selection shown in Fig. 35.
NOTE: When transitioning from low-cooling to high-cooling the
outdoor unit compressor will shut down for 1 minute while the
furnace blower motor BLWM transitions to run at high-cooling
airflow.
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-Y circuit 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. 25.)
3. Two-Stage Thermostat and Two-Speed Cooling
(See Fig. 45 for thermostat connections)
NOTE: The air conditioning relay disable jumper ACRDJ must
be disconnected to allow thermostat control of the outdoor unit
staging. (See Fig. 25.)
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 on low-cooling airflow which is
the true on-board CF selection as shown in Fig. 35. 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 ariflow. High-cooling
airflow is based on the A/C selection shown in Fig. 35.
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. 25.)

THERMIDISTAT MODE

See Fig. 39-42 for Thermidistat 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 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% of
low-cooling airflow which is the true on-board CF selec-
tion as shown in Fig. 35.
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%
of high-cooling airflow. High-cooling airflow is based on
the A/C selection shown in Fig. 35.
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.

SUPER-DEHUMIDIFY MODE

Super-Dehumidify mode can only be entered if the furnace control
is in Thermidistat mode and there is a demand for dehumidifica-
tion. 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 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% 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. 35.
b. High cooling-When the R to Y/Y2 cicuit is closed, R to G
circuit is open, and there is a demand for dehumidifiation,
the furnace blower motor BLWM will drop the blower to
65% of high-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. High-cooling
airflow is based on the A/C selection shown in Fig. 35.
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.

CONTINUOUS BLOWER MODE

When the R to G circuit is closed by the thermostat, the blower
motor BLWM will operate at continuous-blower airflow. Continu-
ous blower airflow selection is initially based on the CF selection
shown in Fig. 35. Factory default is shown in Fig. 40. Terminal
EAC-1 is energized as long as the blower motor BLWM is
energized.
During a call for heat, the blower BLWM will transition the blower
motor BLWM to continuous blower airflow, low-heat airflow, or
the midrange airflow, whichever is lowest. The blower motor
BLWM will remain ON until the main burners ignite then shut
OFF and remain OFF for the blower-ON delay (60 seconds in
low-heat and 35 seconds in high-heat) allowing the furnace heat
exchangers to heat more quickly, then restarts at the end of the
blower-ON delay period at low-heat or high-heat airflow respec-
tively.
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