Wiring - Low Voltage; Low Voltage Connections; Unit Shutdown Feature; Balanced Climate Tm Feature - Bard Q-TEC Q A4D Series Installation Instructions Manual

Wiring – Low Voltage
All 230/208V 1 phase and 3 phase equipment have
dual primary voltage transformers. All equipment leaves
the factory wired on 240V tap. For 208V operation,
reconnect from 240V to 208V tap. The acceptable
operating voltage range for the 240 and 208V taps are:
Tap: 240 Range: 253 – 216
Tap: 208 Range: 220 – 187
NOTE: The voltage should be measured at the field
power connection point in the unit and while
the unit is operating at full load (maximum
amperage operating condition).
For low voltage wiring, an 18 gauge copper, color-
coded cable is recommended. See Table 4 for more
information.

Low Voltage 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 input for cooling.
Y2 terminal is the 2nd Stage input for cooling (if
equipped with an economizer) or Y2 disables Balanced
Climate mode if the Y1-Y2 jumper is removed (see page
30).
B/W1 terminal is the first stage electric heat (if
equipped).
W2 terminal is the 2nd stage of electric heat or
emergency heat (if equipped).
A terminal is the ventilation input. This terminal
energizes any factory-installed ventilation option and
indoor blower.
D terminal is the dehumidification input. This terminal
energizes dehumidification.
L terminal is 24 volt alarm active output.
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. In heating
mode, the reduced airflow provides a warmer supply
air temperature creating more comfortable heat. The
Y1 terminal is the 24VAC input for Balanced Climate
Manual 2100-752C
Page 22 of 41
compressor cooling operation. The Y2 terminal is the
24VAC input for compressor cooling standard operation.
Y1 and Y2 are connected with a brass jumper bar which
can be removed to enable Balanced Climate mode. The
Q-TEC products come standard with two low voltage
strips (one in the blower section and another in the
control panel). Each low voltage strip will need the
Y1-Y2 jumper removed for proper Balanced Climate
operation. Units with an economizer will not have
the brass jumper installed. Refer to vent manuals for
instructions on how Balanced Climate works with each
vent.
NOTE: Units with mechanical dehumidification
require an additional connection to be made
when enabling Balanced Climate. Refer to the
dehumidification supplemental instructions for
this step.
To operate in Balanced Climate mode, a 2-stage
thermostat is required. The lower indoor airflow
operation is overridden by utilizing a 2-stage thermostat.
If the call 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 the blower speed back to the
selected speed.
Refer to page 30 for additional Balanced Climate
requirements and limitations.

Dehumidification Feature

The D terminal is the 24VAC input for dehumidification
operation. 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.
If there is a call for dehumidification and comfort
cooling at the same time, the call for cooling takes
precedence over dehumidification.
If there is a call for dehumidification and first stage
heating, the call for dehumidification takes precedence
over first stage heating. A second stage heating call will
cancel dehumidification.
Ventilation Features (Optional)
See ventilation instructions provided with unit for low
voltage wiring.
Low Ambient Control (Optional)
The low ambient control (LAC) is a pressure switch that
is attached to the liquid line of the system and monitors