Carrier 58MTA - Thermidistat Mode

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 switch the furnace blower motor
BLWM to COOL speed.
NOTE: When transitioning from low-cooling to high-cooling the
outdoor unit compressor will shut down for 1 minute while the
BLWM continues to run at low-cool speed (same speed as
LO-HEAT) until the outdoor unit compressor comes back on at
high speed.
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. 32.)
3. Two-Speed Cooling and Two-Stage Thermostat
(See Fig. 28 and Fig. 52A-G for thermostat connections)
NOTE: The 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 on low-cool speed (same
speed as LO HEAT). 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 on
COOL speed.
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.)
THERMIDISTAT MODE
(See Fig. 52A-D 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 or OFF for more than 48 hours, the furnace
control reverts back to non-Thermidistat mode.
The cooling operation described above also applies to operation
with a Thermidistat. The exceptions are listed below:
a. When the R to G-and-Y1 circuit is closed and there is a
demand for dehumidification, the furnace blower motor
BLWM will continue running at low-cool speed (same
speed as LO HEAT).
b. 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 speed from COOL to HI
HEAT for a maximum of 10 minutes before reverting back
to COOL speed. If there is still a demand for dehumidifi-
cation after 20 minutes, the furnace control CPU will drop
the blower speed back to HI HEAT speed. This alternating
10-minute cycle will continue as long as there is a call for
cooling.
c. 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.
Notes for Fig. 52A-H:
1. Heat pump MUST have a high pressure switch for dual fuel applications.
2. Refer to outdoor equipment Installation Instructions for additional information and setup procedure.
3. Select the ″ZONE″ position on the two-speed heat pump control.
4. Outdoor Air Temperature Sensor must be attached in all dual fuel applications.
5. Dip switch No.1 on Thermidistat should be set in OFF position for air conditioner installations. This is factory default.
6. Dip switch No. 1 on Thermidistat should be set in ON position for heat pump installations.
7. Dip switch No. 2 on Thermidistat should be set in OFF position for single-speed compressor operation.
This is factory default.
8. Dip switch No. 2 on Thermidistat should be set in ON position for two-speed compressor operation.
9. Configuration Option No. 10 ″Dual Fuel Selection″ must be turned ON in all dual fuel applications.
10. NO connection should be made to the furnace HUM terminal when using a Thermidistat.
11. Optional connection. If wire is connected, dip switch No. 1 on furnace control should be set in ON position
to allow Thermidistat/Thermostat to control furnace staging.
12. Optional connection. If wire is connected, ACRDJ jumper on furnace control should be removed to allow
Thermidistat/Thermostat to control outdoor unit staging.
13. Furnace must control its own high-stage heating operation via furnace control algorithm. This is factory default.
14. The RVS Sensing terminal ″L″ should not be connected. This is internally used to sense defrost operation.
15. DO NOT SELECT the ″FURNACE INTERFACE″ or ″BALANCE POINT″ option on the two-speed heat pump
control board. This is controlled internally by the Thermidistat/Dual Fuel Thermostat.
16. Dip switch D on Dual Fuel Thermostat should be set in OFF position for single-speed compressor operation.
This is factory default.
17. Dip switch D on Dual Fuel Thermostat should be set in ON position for two-speed compressor operation.
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