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During dehumidification, the indoor blower speed is
reduced to help with the humidity removal. A humidity
sensing thermostat or humidistat is required to control
dehumidification operation.
If there is a call for dehumidification and comfort
cooling at the same time, the call for cooling takes
precedence over dehumidification.
Ventilation Features (Optional)
See ventilation instructions provided with unit for low
voltage wiring.
Low Ambient Control (LAC)
The low ambient control is a pressure switch that is
attached to the liquid line of the system and monitors
high side system pressure. Operation of the LAC occurs
as outdoor temperatures drop below 60ºF. LAC operation
cycles the condenser fan on/off based on outdoor
temperature.
Outdoor Temperature Switch and Freeze Protection
Thermostat
An outdoor temperature switch and an evaporator
freeze protection thermostat is supplied with all units
that have a low ambient control. The outdoor switch
disables Balanced Climate mode (if enabled) when
the temperature drops below 50ºF. This prevents
potential evaporator coil freeze up issues. For units
with mechanical dehumidification, this switch must
remain disconnected when Balanced Climate mode
is not being used. Refer to unit wiring diagram. The
freeze thermostat cuts out compressor operation if the
evaporator begins to freeze up.
Alarm Relay Feature (Controls Option)
The alarm relay provides a set of NO (normally open)
and NC (normally closed) pilot duty contacts that
operate when the compressor control module locks out
compressor operation because of a high or low system
refrigerant pressure event.
DDC Controls Feature (Controls Option)
The DDC controls option provides additional sensors
that can be used with a field-supplied advanced logic
controller. The DDC controls option contains the
following installed components:
Dirty Filter Switch Indicator (DFS)
The switch is adjustable and measures pressure drop
across the unit filter surface. When pressure drop is
higher than the switch setting, NO contacts are provided
to indicate the filter needs to be serviced. Refer to page
37 for instructions on making switch adjustments.
Discharge Air Sensor
The discharge air sensor provides a temperature reading
of the supply air leaving the unit. The sensor is a 10K
OHM @ 77°F measuring device. It is installed in the
supply airstream in the heater bracket.
Airflow Switch
The airflow switch measures the pressure differential
between the blower inlet and outlet. It is located directly
above the blower partition. Relay contacts (NO) are
provided for the DDC controls option that indicates the
indoor blower assembly needs to be serviced.
Compressor Current Sensor
The compressor current sensor indicates when the
compressor is operational by measuring amp draw. It
is located inside the unit control panel. Relay contacts
(NO) are provided to indicate the compressor is not
operating.
See Table 3 for low voltage connections for DDC control.
TABLE 3
Low Voltage Connections for DDC Control
Standard Units
Fan Only
Energize G
1st Stage
Cooling Mode/
Energize Y1, G
Balanced Climate
Energize Y2
to override
2nd Stage
Balanced Climate
Cooling Mode
mode when
Y1-Y2 jumper is
removed
1st Stage Heating
Energize B/W1
2nd Stage Heating
Energize B/W1, W2
(if employed)
Ventilation
Energize A
Dehumidification
Energize D
(if employed)
Energize, G, W2,
Emergency Heat
W3
Units w/
Economizers
Energize G
Energize Y1, G
Energize Y1, Y2, G
Energize B/W1
Energize B/W1, W2
Energize A
Energize D
Energize, G, W2,
W3
Manual 2100-711F
Page
19 of 45
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