Specifications

Manual 2100-317
Page 25
SEQUENCE OF OPERATION
COOLING
When thermostat system switch is placed in COOL it
completes a circuit from “R” to “O”, energizing the
reversing valve solenoid. On a call for cooling, the
cooling bulb completes a circuit from “R” to “Y”,
energizing the compressor contactor starting the
compressor. The “R” to “G” circuit for blower operation
is automatically completed on any call for cooling
operation, or can be energized by manual fan switch on
subbase for constant air circulation.
HEATING WITHOUT ELECTRIC HEAT
When thermostat system switch is placed in HEAT it
opens the circuit from “R” to “O”, de-energizing the
reversing valve solenoid. On a call for heating, it
completes a circuit from “R” to “Y”, energizing the
compressor contactor starting the compressor. The “R: to
“G” circuit for blower operation is automatically
completed on any call for heating operation, or can be
energized by manual fan switch on subbase for constant
air circulation.
HEATING WITH ELECTRIC HEAT
The first stage of heating is the same as heating without
electric heat. When the second stage thermostat bulb
makes, a circuit is completed between “R” to “W1”,
energizing the heater package time delay relay(s). The
electric heater elements will remain energized until the
second stage bulb is satisfied at which time the circuit
between “R” to “W1” will open de-energizing the heat
package time delay relay(s).
EMERGENCY HEAT
When thermostat system switch is placed in EMER, the
compressor circuit “R” to “Y” is locked out. Control of
the electric heaters is from “R” to “W1” through the
thermostat second stage heating bulb. Blower operation
is controlled by an interlock circuit with the electric
heater time delay relay and the blower control. The
electric heater elements will remain energized until the
second stage bulb is satisfied at which time the circuit
between “R” and “W1” will open de-energizing the heat
package time delay relay (s) and the blower.
LOCKOUT CIRCUITS
Each unit has two separate lockout circuits, one for the
high pressure switch and one for the low pressure switch.
Lockout circuits operate the same in either cooling or
heating operation.
High pressure lockout circuit: Consists of a normally
closed switch and an impedance circuit. As long as the
switch is closed the circuit “R” to “Y” which controls the
compressor contactor is complete. If the pressure rises
above the set point of the switch (approximately 355
PSIG) the switch will open and the impedance circuit will
lockout the circuit even after the pressure drops below the
set point and switch closes. The circuit will remain in
lockout until the thermostat system switch is set in the
OFF position and all low voltage to the control circuit is
off.
Low pressure lockout circuit: Consists of a normally
open switch and a relay used in a latching circuit. As
long as the switch is open the circuit “R” to “Y” which
controls the compressor contactor is complete. If the
pressure drops below the set point of the switch
(approximately 15 to 27 PSIG) the switch will close and
the relay will lockout the circuit even after the pressure
rises above the set point and switch opens. The circuit
will remain in lockout until the thermostat system switch
is set in the OFF position and all low voltage to the
control circuit is off.
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.
SYSTEM START-UP
Step 1 – Close disconnect switch(es) and set the
thermostat to cool and the temperature to the
highest setting.
Step 2 – Check for proper airflow across the indoor coil.
Step 3 – Connect the service gauges and allow the unit
to run for at least 10 minutes or until pressures
are stable. Check pressures to the system
pressure table attached to the unit service panel.
Step 4 – Fill out Ground Source Heat Pump
Performance Report.