Bard W24G4 Installation Instructions Manual page 22

For low voltage wiring, an 18 gauge copper, color-
coded cable is recommended. See Table 5 for more
information.
460 Volt Units
All models are equipped with single primary voltage
transformers and no rewiring is required.
Direct Digital Controls (DDC)
For total and proper control using DDC, a total of six
controlled outputs are required (five if no ventilation is
installed).
TABLE 3
Low Voltage Connections for DDC Control
Standard Units
Fan Only Energize G
1st Stage
Cooling Mode/Bal- Energize Y1, G
anced Climate
Energize Y2 to
overide Bal-
2nd Stage anced Climate
Cooling Mode mode when
Y1-Y2 jumper is
removed
Gas Heating Energize B/W1
Ventilation Energize A
Dehumidification
Energize D
(if employed)
Low Voltage (24VAC) Connections
These units use a 24-volt AC low voltage circuit.
C terminal is the 24VAC common and is grounded.
G terminal is the indoor blower input.
Y1 terminal is the 1st Stage cooling input. Economizer
stage when used. Balanced Climate stage when used.
Y2 terminal is the 2nd Stage cooling input. Compressor
cooling stage when economizer or Balanced Climate is
used.
B/W1 terminal is the gas heat.
A terminal is the ventilation option input. This
terminal energizes any factory-installed ventilation
option and indoor blower.
D terminal is the dehumidification input. If installed, this
terminal energizes any factory-installed dehumidification
option.
L terminal is 24 volt alarm active output.
Manual 2100-721B
Page 22 of 54
Unit Shutdown Feature (Standard on All Models)
The RT terminal is the 24VAC transformer output,
and the R terminal is the 24VAC hot terminal for the
operation of the equipment. RT and R are connected
with a brass jumper bar which can be removed and RT
and R connected to an external NC (normally closed)
contact such as a fire/smoke detector that will cause
shutdown of the equipment upon activation.
Balanced Climate™ Feature (Standard on All Models)
All units are equipped with the capability of running
in Balanced Climate mode. This mode is designed to
enhance the comfort level by reducing the indoor airflow
amount and extending the run time to help extract more
humidity during cooling operation. The Y1 terminal
is the 24VAC input for Balanced Climate compressor
Units w/
cooling operation. The Y2 terminal is the 24VAC input
Economizers
for compressor cooling standard operation. Y1 and Y2
are connected with a brass jumper bar which can be
Energize G
removed to enable Balanced Climate mode. Units with
an economizer will not have the brass jumper installed.
Energize Y1, G
Refer to vent manuals for instructions on how Balanced
Climate works with each vent.
To operate in Balanced Climate mode, a 2-stage cooling
thermostat is required. The lower indoor airflow operation
is overridden by utilizing a 2-stage thermostat. If the call
Energize Y1, Y2, G
for cooling is not satisfied within a given time frame or
temperature differential (specified by the thermostat), the
thermostat will send a signal to Y2 which then increases
Energize B/W1 the blower speed back to the selected speed. See pages
43 – 44 for blower speed selection options.
Energize A
In units with an economizer vent installed, Balanced
Climate mode should not be used. The Y1 and Y2
Energize D
jumper must remain installed.
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. See Supplemental
Instructions 7960-867 for additional information on
dehumidification unit 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