Manual 2100-488
Page
18 of 26
PHASE MONITOR
All units with three phase scroll compressors are
equipped with a 3 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.
SERVICE HINTS
1. Caution owner/operator to maintain clean air filters at
all times. Also, not to 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. Switching to heating cycle at 75°F or higher outside
temperature may cause a nuisance trip of the remote
reset high pressure switch. Turn thermostat off, then
on to reset the high pressure switch.
3. The heat pump wall thermostats perform multiple
functions. Be sure that all function switches are
correctly set for the desired operating mode before
trying to diagnose any reported service problems.
4. Check all power fuses or circuit breakers to be sure
they are the correct rating.
5. Periodic cleaning of the outdoor coil to permit full
and unrestricted airflow circulation is essential.
SEQUENCE OF OPERATION
OCCUPIED MODE
VENTILATION SEQUENCE
– The ERV and indoor
blower will be continuously energized when the A1
terminal is energized.
COOLING SEQUENCE
– On a call for cooling, the
compressor of the unit is energized to provide cooling.
A call for cooling cancels dehumidification mode.
Cooling mode is only available when the timer is
energized. See Figure 13.
Circuit R-Y makes at thermostat pulling in compressor
contactor, starting the compressor and outdoor motor.
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. Refer to Figure 13.
HEATING SEQUENCE
– On a call for heating, the
compressor and reversing valve of the unit are
energized to provide heat pump heating. If the room
temperature falls below the 2nd stage heating set point
backup electric heat is energized. Heat pump heating is
only available when the timer is energized. If heating is
energized any call for dehumidification is ignored. If
dehumidification is already energized a call for 2nd
stage heating is needed to cancel dehumidification
mode.
A 24V solenoid coil on reversing valve controls heating
cycle operation. A thermostat demand for heat
completes R-W1 circuit, pulling in compressor
contactor starting compressor and outdoor motor. R-G
also make starting indoor blower motor.
DEHUMIDIFICATION SEQUENCE
– On a call for
dehumidification the compressor and three way valve of
the unit are energized to provide dehumidification.
Dehumidification mode will continue until the
humidistat is satisfied. If the room temperature falls
below 1st stage heating setpoint, electric heat will be
energized by the room thermostat and cycle to maintain
room temperature. If 2nd stage heating setpoint is
reached, dehumidification is de-energized and heat
pump heating is energized. A call for cooling cancels
dehumidification mode. Refer to Figure 14.
UNOCCUPIED MODE
Cooling, heating, emergency heat and ventilation are
inhibited.
DEHUMIDIFICATION SEQUENCE
– On a call for
dehumidification the compressor and three way valve of
the unit are energized to provide dehumidification.
Dehumidification mode will continue until the
humidistat is satisfied. If the room temperature falls
below 65 degrees and dehumidification is energized,
electric heat will be energized by the return air
thermostat and cycle to maintain room temperature.
See Figure 14.
OTHER CONTROL SEQUENCE
Any time the indoor coil temperature falls below 32
degrees the compressor will be de-energized until the
coil temperature rises above 57 degrees.
PRESSURE SERVICE PORTS
High and low pressure service ports are installed on all
units so that the system operating pressures can be
observed. Pressure tables can be found later in the
manual covering all models on both cooling and heating
cycles. It is imperative to match the correct pressure
curve to the unit by model number.
