Dehumidification Feature; Ventilation Features; Low Ambient Control (Lac); Outdoor Temperature Switch And Freeze Protection Thermostat - Bard W42AC-B Installation Instructions Manual

back to the selected speed. See pages 33 – 35 for
blower speed selection options.
Refer to page 24 for additional Balanced Climate
requirements and limitations.
Dehumidification Feature (Optional)
The D terminal is the 24VAC input for dehumidification
operation on dehumidification hot gas reheat equipped
units. When 24VAC is applied to the D terminal, a
3-way valve solenoid is energized. The reheat coil
located behind the evaporator coil is then active to
reheat the supply air during cooling mode. This allows
humidity to be removed from the air entering the unit
without a large amount of sensible cooling capacity.
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.
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 pressure. Operation of the LAC occurs as
outdoor temperatures drop below 60°F. LAC operation
cycles the condenser fan on/off based on pressure
changes caused by outdoor temperature changes.
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 50°F. 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 34 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 4 for low voltage connections for DDC
control.
TABLE 4
Low Voltage Connections for DDC Control
Standard Units
Fan Only Energize G
1st Stage
Cooling Mode/ Energize Y1, G
Balanced Climate
Energize Y2 to
overide Balanced
2nd Stage Climate mode
Cooling 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)
Units w/
Economizers
Energize G
Energize Y1, G
Energize Y1, Y2, G
Energize B/W1
Energize B/W1, W2
Energize A
Energize D
Manual 2100-692E
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