Dehumidification Feature; Ventilation Features; Alarm Relay Feature; Ddc Controls Feature - Bard W42AC-A Installation Instructions Manual

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.
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 and NC contacts are
provided to indicate the filter needs to be serviced.

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 2100-692
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