2.Cooling Mode
The thermostat “calls for cooling.”
a.Single-Speed Cooling
(See Fig. 25 - 32 for thermostat connections)
The thermostat closes the R-to-G-and-Y circuits. The R-to- Y circuit starts the outdoor unit, 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 when the blower motor BLWM is operating. When the thermostat is satisfied, the R-to-G-and-Y circuits are opened. The outdoor unit will stop, and the furnace blower motor BLWM will continue operating on the COOL speed for an additional 90 seconds. Jumper Y/Y2 to DHUM to reduce the cooling off-delay to 5 seconds. (See Fig. 24.)
b.Two-Speed Cooling
(See Fig. 25 - 32 for thermostat connections.)
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 FAN). The R-to-Y1-and-Y2 circuits start the outdoor unit on high-cooling speed, and the R-to-Gand- 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. 24.)
3.Thermidistat Mode
(See Fig. 26-29 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 2. 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 FAN).
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 HEAT for a maximum of 10 minutes before reverting back to COOL speed. If there is still a demand for dehumidification after 20 minutes, the furnace control CPU will drop the blower speed back to 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.
4.Continuous Blower Mode
When the R-to-G circuit is closed by the thermostat, the blower motor BLWM will operate on continuous-blower speed (can be adjusted to FAN, HEAT, or COOL speed) at the thermostat. Factory default is FAN speed. Terminal EAC-1 is energized as long as the blower motor BLWM is energized. During a call for heat, the blower BLWM will stop during igniter warm-up (17 seconds), ignition (7 seconds), and blower-ON delay (25 seconds), allowing the furnace heat exchangers to heat up more quickly, then restarts at the end of the blower-ON delay period at HEAT speed.
In heating, the furnace control CPU will hold the blower motor BLWM at HEAT speed during the selected blower-OFF delay period before reverting to continuous-blower speed. When the thermostat “calls for low-cooling,” the blower motor BLWM will switch to operate at low-cool speed (same speed as FAN). When the thermostat is satisfied, the blower motor BLWM will operate an additional 90 seconds on low-cool speed (same speed as FAN) before reverting back to continuous-blower speed.
When the thermostat “calls for high-cooling”, the blower motor BLWM will operate at COOL speed. When the thermostat is satisfied, the blower motor BLWM will operate an additional 90 seconds on COOL speed before reverting back to continuous-blower speed.
When the R-to-G circuit is opened, the blower motor BLWM will continue operating for an additional 5 seconds, if no other function requires blower motor BLWM operation.
Continuous Blower Speed Selection from Thermostat -To select different continuous-blower speeds from the room thermostat, momentarily turn off the FAN switch or pushbutton on the room thermostat for 1-3 seconds after the blower motor BLWM is operating. The furnace control CPU will shift the continuous-blower speed from the factory setting of FAN to HEAT speed. Momentarily turning off the FAN switch again at the thermostat will shift the continuous-blower speed from HEAT to COOL. Repeating the procedure will shift the continuous-blower speed from COOL to FAN speed. The selection can be changed as many times as desired and is stored in the memory to be automatically used following a power interruption.
