343633-YIM-B-0408
14
Johnson Controls Unitary Products
SEQUENCE OF OPERATION FOR DEM
MODELS
COOLING
The following sequences of operation are based on using a
standard single-stage cooling thermostat.
WITH POWER TO UNIT AND THERMOSTAT IN COOLING
MODE.
1.
If the fan switch on the thermostat is in the “ON” position,
the 24 volts at “G” will be sent to the indoor motor and the
blower will operate at the selected airflow. If the fan switch
is in the “AUTO” position, the blower will operate at the
selected airflow only when there is a call for cooling by the
thermostat.
2.
On a call for cooling, the thermostat will send 24 volts to “Y”
on the fan control board. The 24 volt signal will energize
contactor “M1", and power will be supplied to the
compressor and outdoor fan motor. If the fan switch on the
thermostat is on the ”AUTO" position, the thermostat will
also send a 24 volt signal to “G” on the fan control board
and the indoor blower will operate as indicated in step 1.
3.
When the demand for cooling has been satisfied, the “M1"
contactor will be de-energized when the 24 volt ”Y" signal
is removed. If the fan switch on the thermostat is in the
“ON” position, the indoor blower
will continue to run. If the
fan switch is in the “AUTO” position, the 24 volt “G” signal
will be removed, and after a 30 second delay, the indoor
blower motor will shut down.
HEATING
WITH POWER TO UNIT AND THERMOSTAT IN HEATING
MODE.
1.
If the fan switch on the thermostat is in the “ON” position,
the 24 volts at “G” will be sent
to the indoor motor and the
blower will operate at the selected airflow. If the fan switch
is in the “AUTO” position,
the blower will operate at the
selected airflow only when there is a call for heating by the
thermostat.
2.
On a call for heating, the thermostat will send 24 volts to
“W1" on the fan control board. The 24 volts signal will
energize relay ”K2" on the fan control board, and the first
stage of electric heat will be energized. The indoor blower
will operate as indicated in step 1.
3.
On units with 2 (two) stages of electric heat, the second
bank of heaters will be energized by a 24 volt signal to “W2"
on the fan control board. After a 20 second delay, the third
bank of heaters will be energized if the unit is so equipped.
4.
When the heating demand is satisfied, the electric heat will
be de-energized when the 24 volt “W1" and ”W2" signals
are removed. If the fan switch on the thermostat is in the
“ON” position, the indoor blower will continue to run. If the
fan switch is in the “AUTO”
position, the indoor motor will
shut off after the appropriate time delay.
Please refer to Tables 13 and 14 for more information.
