Manual 2100-790
Page
28 of 49
High and Low Pressure Switch
All W**H Series wall-mounted heat pump models
are supplied with a remote reset for the high and low
pressure switch. If tripped, this pressure switch may be
reset by turning the thermostat off then back on again.
Three Phase Scroll Compressor Start
Up Information
Scroll compressors, like several other types of
compressors, will only compress in one rotational
direction. Direction of rotation is not an issue with
single phase compressors since they will always start
and run in the proper direction.
However, three phase compressors will rotate in either
direction depending upon phasing of the power.
Since there is a 50-50 chance of connecting power
in such a way as to cause rotation in the reverse
direction, verification of proper rotation must be made.
Verification of proper rotation direction is made by
observing that suction pressure drops and discharge
pressure rises when the compressor is energized.
Reverse rotation also results in an elevated sound level
over that with correct rotation, as well as substantially
reduced current draw compared to tabulated values.
Verification of
proper rotation
must be made at the time
the equipment is put into service. If improper rotation
is corrected at this time, there will be no negative
impact on the durability of the compressor. However,
reverse operation for over 1 hour may have a negative
impact on the bearing due to oil pump out.
NOTE:
If compressor is allowed to run in reverse
rotation for several minutes, the compressor’s
internal protector will trip.
All three phase ZP compressors are wired identically
internally. As a result, once the correct phasing is
determined for a specific system or installation,
connecting properly phased power leads to the same
Fusite terminal should maintain proper rotation
direction.
The direction of rotation of the compressor may be
changed by reversing any two line connections to the unit.
Phase Monitor
All units with three phase scroll compressors are
equipped with a three phase line monitor to prevent
compressor damage due to phase reversal.
The phase monitor in this unit is equipped with two
LEDs. If the Y signal is present at the phase monitor
and phases are correct, the green LED will light.
If phases are reversed, the red fault LED will be lit and
compressor operation is inhibited.
If a fault condition occurs, reverse two of the supply
leads to the unit.
Do not reverse any of the unit factory
wires as damage may occur.
Condenser Fan Operation
NOTE:
Certain models may be equipped with a low
ambient control (LAC), and if so, the condenser fan
motor will have a delayed start until system refrigerant
operating pressure builds up. After starting, the fan
motor may or may not cycle depending upon ambient
conditions. This is normal operation.
Sequence of Operation
Cooling
Circuit R-Y1 makes at thermostat pulling in compressor
contactor, starting the compressor and outdoor motor.
(See
NOTE
under
Condenser Fan Operation
concerning models equipped with low ambient control.)
The G (indoor motor) circuit is automatically completed
on any call for cooling operation or can be energized by
manual fan switch on subbase for constant air circulation.
Heating
A 24V solenoid coil on reversing valve controls heating
cycle operation. Two thermostat options, one allowing
“Auto” changeover from cycle to cycle and the other
constantly energizing solenoid coil during heating
season—thus eliminating pressure equalization noise
except during defrost, are to be used.
On “Auto” option a circuit is completed from R-B/W1 and
R-Y1 on each heating “on” cycle, energizing reversing
valve solenoid and pulling in compressor contactor
starting compressor and outdoor motor. R-G also make
starting indoor blower motor. Heat pump heating cycle
now in operation.
The second option has no “Auto” changeover position, but
instead energizes the reversing valve solenoid constantly
whenever the system switch on subbase is placed in
“Heat” position, the “B” terminal being constantly
energized from R. A thermostat demand for heat
completes R-Y1 circuit, pulling in compressor contactor
starting compressor and outdoor motor. R-G also make
starting indoor blower motor.
On a call for 2nd stage heating, circuit R-W2 makes
at the thermostat pulling in the heat contactor for the
strip heat and blower operation. On a call for third
stage heat, R-B/W1 breaks, dropping out heat pump,
and R-W3 makes, bringing on second heat contactor, if
so equipped.
Dehumidification and Electronic Expansion Valve (EEV)
For information on dehumidification and EEV
operations, refer to latest version of dehumidification
supplemental instructions 7960-828.
Balanced Climate
TM
Mode
Balanced Climate™ is a great comfort feature that can
easily be applied under any normal circumstances. If
the Bard heat pump system is being set up in a typical
environment where 72°F is the lowest cooling setpoint,
remove the Y1/Y2 jumper and install a 2-stage cooling
