Manual 2100-549Q
Page
33 of 69
SEQUENCE OF OPERATION
COOLING PART LOAD
– Circuit R-Y1 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.
COOLING FULL LOAD
– Circuit R-Y1 & Y2 makes at
the thermostat energizing the 2nd stage solenoid in the
compressor. The default position of the compressor
staging solenoid is non-energized. The compressor will
run at low capacity until this solenoid is energized.
HEATING STAGE 1
– 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 and thus eliminating pressure
equalization noise except during defrost, are to be
used. On “Auto” option a circuit is completed from
R-B 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 Stage 1 heat completes
R-Y1 circuit, pulling in compressor contactor starting
compressor and outdoor motor. R-G also make starting
indoor blower motor.
HEATING STAGE 2
– Circuit R-Y1 & Y2 makes at the
thermostat energizing the 2nd stage solenoid in the
compressor.
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. It is imperative to match
the correct pressure table to the unit by model number.
Upper and lower service doors must be attached to
obtain proper reading.
This unit employs high-flow Coremax valves instead of
the typical Shrader type valves.
WARNING! Do NOT use a Schrader valve core removal
tool with these valves. Use of such a tool could result
in eye injuries or refrigerant burns!
To change a Coremax valve without first removing the
refrigerant, a special tool is required which can be
obtained at www.fastestinc.com/en/SCCA07H. See the
replacement parts manual for replacement core part
numbers.
LOWERING OUTDOOR FAN SPEED FOR
SOUND
Supplied in the literature assembly is a fan control
resistor assembly that can be installed to lower the fan
speed for reduced sound performance. This resistor
assembly is to be installed in series with the outdoor
fan control thermistor to change the temperature curve
that the fan logic control sees.
It is anticipated that a 2-3% drop in system capacity
and efficiency will be seen when this resistor is
installed.
To install the resistor assembly:
1. Locate fan control resistor assembly in literature
packet hanging on right inside door of unit.
2. Throw main power disconnect to the “OFF”
position to eliminate risk of injury or death due to
electrical shock.
3. Remove four (4) screws that retain the control
panel cover to the unit.
4. Locate fan logic control board.
5. Locate one of the red leads of the fan control
thermistor where it attaches to the fan logic control
and remove it.
6. Install resistor in-line with the thermistor lead
removed in Step #5, and then connect back onto
the fan logic control board.
DEFROST CYCLE
The defrost cycle is controlled by temperature and time
on the solid state heat pump control. See Figure 20 on
page 34.
When the outdoor temperature is in the lower
40°F temperature range or colder, the outdoor coil
temperature is 32°F or below. This coil temperature
is sensed by the coil temperature sensor mounted near
the bottom of the outdoor coil. Once coil temperature
reaches 30°F or below, the coil temperature sensor
sends a signal to the control logic of the heat pump
control and the defrost timer will start accumulating
run time.
After 30, 60 or 90 minutes of heat pump operation at
30°F or below, the heat pump control will place the
system in the defrost mode. Factory default setting is
90 minutes.
During the defrost mode, the refrigerant cycle switches
back to the cooling cycle, the outdoor motor stops,
electric heaters are energized and hot gas passing
through the outdoor coil melts any accumulated frost.
When the temperature rises to approximately 57°F, the
coil temperature sensor will send a signal to the heat
pump control which will return the system to heating
operations automatically.
