Manual 2100-769A
Page
25 of 50
control panel where the connections are made. (The
field wire shield can be removed for wire installation.)
If field power is supplied to the right of side of the unit,
the low voltage wires can be run under the field wire
shield to access the low voltage terminal strip.
When field wires are supplied through the back of the
unit, flexible conduit must be extended through the
back of the unit and terminate into the knock-outs on
the upper control panel (see Figure 19).
Wiring – Low Voltage
All 1-phase and 3-phase equipment, rated 230/208V,
have dual primary voltage terminals on the low-
voltage, step-down transformer. The 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 7 on page 26 for
more information.
Low Voltage Connections
These units use a 24-volt AC low voltage circuit.
R
terminal is the
24VAC hot
.
C
terminal is the
24VAC common and is grounded.
G
terminal is the
indoor blower input
.
Y1
terminal is the
compressor part load input.
Y2
terminal is the
compressor full load input.
B/W1
terminal is the
reversing valve input
. The
reversing valve must be energized for heating mode.
W2
terminal is the
1st stage electric heat
(if equipped).
1st stage electric heat can be operated simlutaneously
with the heat pump operating.
W3
terminal is the
2nd stage of electric heat
or
emergency heat
(if equipped). When W3 terminal is
energized, it locks out compressor operation to limit
discharge air temperature and required branch circuit
ampacity.
A
terminal is the
ventilation input
. This terminal
energizes any factory-installed ventilation option and
indoor blower.
L
terminal is
24 volt alarm active output
.
For units equipped with an alarm relay:
1 terminal
is the
normally closed contact on the relay.
2 terminal
is the
normally open contact on the relay.
3 terminal
is the
common contact on the relay.
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.
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.
The LAC kit also comes with an evaporator freeze
protection thermostat that cuts out the compressor if the
evaporator begins to freeze up.
If the unit is being installed with any ventilation package,
a Bard LAC kit must be installed.
Failure to utilize an
LAC with any heat pump can cause coil freeze up.
Freeze Protection Thermostat
An evaporator freeze protection thermostat is supplied
with all units that have a low ambient control. 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 defrost board locks out compressor
operation because of a high or low system refrigerant
pressure event.
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
45 for instructions on making switch adjustments.
