Manual 2100-647D
Page
18 of 36
HIGH PRESSURE AND LOW PRESSURE
SWITCHES
All H**A/H**L wall mounted air conditioner series
models are supplied with a remote reset for the high
and low pressure switches. The first time the high
or low pressure switches are tripped, they will reset
automatically. If tripped a second time, reset the
switches by turning the thermostat off, then back on
again, resetting the compressor control module.
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 an extended period of time, the
compressor’s internal protector will trip.
All three phase 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: These models are equipped with a low ambient
control (LAC). The condenser fan motor may 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.
The condenser fan motor on
230/208 volt, one and three phase, 60 HZ units is
a two-speed motor that comes factory wired on high
speed for peak performance. If ambient conditions
permit, it can be reconnected to low speed (red wire)
for lower sound level. See unit wiring diagram.
SERVICE HINTS
1. Caution owner/operator to maintain clean air filters
at all times and to not needlessly close off supply
and return air registers. This reduces airflow
through the system, which shortens equipment
service life as well as increasing operating costs.
2. Check all power fuses or circuit breakers to be sure
they are the correct rating.
3. Periodic cleaning of the outdoor coil to permit full
and unrestricted airflow circulation is essential.
SEQUENCE OF OPERATION
COOLING – 24VAC from MV controller at terminal 4 (Y)
pulls in compressor contactor, starting the compressor
and outdoor motor. (See
NOTE
under Condenser
Fan Operation concerning the low ambient control.)
Terminal 9 (G) indoor motor circuit is energized by
the MV controller on any call for cooling operation or
can be energized by manual fan switch on subbase for
constant air circulation. A call for heating from the MV
controller pulls in heat contactor, activating the strip
heat and blower operation. On a call for second stage
heat, R-W2 makes bringing on second heat contactor,
if so equipped. See Table 1 on following page.
COMPRESSOR CONTROL MODULE
The compressor control module (CCM) is standard on
all models covered by this manual. The compressor
control module is an anti-short cycle/lockout timer with
high and low pressure switch monitoring and alarm
relay output.
