Product data

Controls — systems using Under Ceiling,
Cassette or Satellite fan coils
Automatic air sweep
All Under Ceiling units are equipped with an automatic air sweep feature, which automatically directs the airflow
louvers up and down to provide optimum room air circulation. If the auto sweep feature is not desired, temporarily
start the auto sweep using the remote thermostat (press Air Sweep button). When the louvers are in the desired
position, turn auto sweep off (press Air Sweep button again) to hold them in that position.
Operating mode memory
After the system is turned off or after a power failure, the system remains in the last operating mode selected. When
the system is turned back on, or when power is automatically restored, operation continues in the same operating
mode as when the system shut down.
Automatic operation (auto) mode
If auto mode is selected, the system automatically switches over the operating mode from heating to cooling, or
from cooling to heating depending on the selected temperature. Auto mode also controls fan speed if not manually
overridden.
NOTE:
Between the cooling cycle and the heating cycle there is a neutral zone of approximately 2° F above and
2° F below the selected temperature when only the fan is operating.
Operating sequence
Ceiling-suspended fan coil units have a relay board which controls system operation in response to the room
thermostat. The user may manually select any one of 3 fan speeds for unit operation. Ceiling-suspended systems
may be equipped with an accessory power ventilation kit and/or condensate pump.
Fan operation
— Fan speed can be selected by pressing the fan button (high, medium, or low speed choices). The
fan(s) is capable of operation when unit mode is set on cooling, heating, or auto mode. When the fan(s) is operating
in medium or high speed and the unit is equipped with the power ventilation kit, the ventilation fan will operate to
provide fresh air. If the mode is set to the AUTO position, then the fan will operate with the outdoor unit
compressor.
Cooling mode operation
— When the room thermostat senses a demand for cooling, the fan coil relay board is
energized. The indoor fan(s) will start in the selected speed (if it is not already operating). The reversing valve will
energize and switch to the cooling position. The internal condensate pump (if so equipped) runs whenever the
reversing valve is energized and/or the unit is in cooling. As long as the condensate float switch and freeze
protection thermostat are closed, the cooling relays in the fan coil unit will close. This energizes the compressor and
outdoor fan in the outdoor unit. The compressor will continue to operate until the room thermostat is satisfied.
When the cooling demand is satisfied, the compressor and outdoor fan will stop. If the system is in the AUTO mode,
the indoor fan will stop with the compressor. If the unit has the accessory ventilation kit, the ventilation fan will
operate whenever the indoor fan is set for medium or high speed.
Heat pump operation
— When the room thermostat senses a demand for heating, the fan coil relay board is
energized. The indoor fan will start in the selected speed (if not already operating), and the reversing valve will not
be energized. The internal condensate pump (if supplied) and freeze protection thermostat are not operated during
heating operation. The control relay (CR2) closes, and the compressor and outdoor fan are energized through the
defrost board (DFB), which is located in the outdoor unit. The microprocessor logic in the DFB is energized when
the compressor starts, and the defrost timer runs. Once every 90 minutes (factory default setting) of compressor run
time, the DFB logic checks the defrost thermostat (DFT). If the DFT is open, the unit continues in heating operation.
If the DFT is closed, the DFB switches the unit to defrost mode. The timing on the DFB may be set at either 30, 50,
or 90 minutes.
Defrost
— The DFB energizes the RVS (reversing valve solenoid), and the reversing valve switches to the cooling
position. The K1 relay on the DFB opens and the outdoor fan stops. The W2 contact on the DFB is also energized,
which in turn energizes the defrost relay on the fan coil relay board, turns off the electric heater and stops the indoor
fan. The DFB logic checks the 10-minute defrost timer and the DFT. If the DFT opens in less than 10 minutes, the (MORE)