Manual 2100-738C
Page
40 of 73
Cooling
A 24V solenoid coil on the reversing valve controls
the cooling cycle operation. There are two different
thermostat options: One allows for “Auto” changeover
from cycle to cycle and the other is "Manual"
changeover. The Auto changeover mode will cause the
reversing valve solenoid to cycle with each cooling call
and may cause a “swooshing sound” with refrigerant
equalization at the end of each cycle.
Part Load Cooling
On a call for Part Load Cooling by the thermostat, it
completes a circuit from R to Y1, O and G for part
load cooling. Y1 starts the compressor, O energizes the
reversing valve and G starts the indoor blower.
Full Load Cooling
On a call for Full Load Cooling by the thermostat, it
completes the same as Part Load Cooling above, but
also includes a signal to Y2. Signal Y2 energizes the
staging solenoid on the side of the compressor and the
signal also goes to the indoor blower to ramp-up the
airflow.
Heating
Part Load Heating
On a call for Part Load Heating by the thermostat, it
completes a circuit from R to Y1 and G. Y1 starts the
compressor and G starts the indoor blower.
Full Load Heating
On a call for Full Load Heating by the thermostat, it
completes the same as Part Load Heating above, but
also includes a signal to Y2. Signal Y2 energizes the
staging solenoid on the side of the compressor and the
signal also goes to the indoor blower to ramp-up the
airflow.
Geothermal Logic Control
When the green status light blinks, this indicates that
24 volt power is applied to the board and the controller
is running in normal operation.
On initial power up and call for compressor, a 5-minute
delay plus a random start delay of 0 to 60 seconds is
applied. After the random delay, the compressor relay
is energized (terminals CC and CCG). When the Y input
opens, the compressor de-energizes.
NOTE The time delay and random start can be
disabled by removing the Test jumper on the
geothermal logic control board. However, this
is not recommended. This is only intended to
be a function for factory run-in processes.
SEQUENCE OF OPERATION
Alarm Output
The L terminal has 24 volts applied when a hard
lockout occurs. This can be used to drive a fault light
or low voltage relay.
NOTE Both high and low pressure switch controls are
inherently automatic reset devices. The high
pressure switch and low pressure switch cut
out and cut in settings are fixed by specific
heat pump model. The lockout features,
both soft and manual, are a function of the
compressor logic control board.
Freeze Stat
When the Y signal is sent to the logic control board,
the signal will travel from the dehum board through the
freeze stat and give 24 volt power at the Y1 terminal of
the compressor logic control board. Following that, the
output will energize 10 seconds prior to CC output that
starts the compressor.
Anti-Short Cycle Timer
After compressor shutdown or power disruption,
a 5-minute timer is applied which prevents the
compressor from operating.
High Pressure Switch
(Terminals HP1 and HP2) Circuit will be proved
as "closed" prior to energizing A or CC terminals.
If pressure switch opens, compressor will go into
soft lockout mode and compressor operation will be
terminated; green fault light will be illuminated. Logic
control will then go through 5-minute delay on break
plus random start sequence. If no fault is found on
next run cycle, compressor will continue operation. If
fault reoccurs, a hard lockout will be initiated and fault
signal is sent to L terminal.
Low Pressure Switch
(Terminals LP1 and LP2) Circuit will be proved as
"closed" prior to energizing A or CC terminals. The
conditions of the LP terminals will then be ignored for
the first 90 seconds after a demand for compressor
operation. Following this 90-second period, if pressure
switch opens, compressor will go into soft lockout
mode and compressor operation will be terminated;
orange fault light illuminated. The control board
will then go through a 5-minute delay on break plus
random start sequence. If no fault is found on next
run cycle, compressor will continue operation. If fault
reoccur, hard lockout occurs, and fault signal is sent to
L terminal.
Flow Switch
(Terminals FS and FS2) Circuit will be proved as
"closed prior to energizing CC terminal. If flow switch
opens, compressor will go into soft lockout mode and
