38
7.0 COMPONENTS & CONTROLS
7.8 High Pressure
Control (HPC)
Sensing of the compressor discharge pressure is
accomplished by a conventional automatic reset
pressure control that is brazed into the compressor
discharge line. The HPC leads connect directly to
the inverter which communicates with the Variable
Speed Outdoor Control (VSODC). The contacts
on the high pressure control (HPC) open when the
compressor discharge pressure of approximately
610 PSIG [4206 kPa] and automatically close when
the pressure drops below approximately 420 PSIG
[2896 kPa]
.
7.9 Liquid Pressure
Transducer
(-)P20 heat pumps
are equipped with
a liquid pressure
transducer for
the purpose of
measuring the liquid
pressure at the
outdoor unit. The
output of this device
is a 0.5 – 4.5VDC
signal that the
VSODC converts to
a pressure used for
calculating the liquid subcooling level. The VSODC
communicates the liquid pressure and subcooling
level to the EcoNet™ Control Center where they
are displayed on outdoor unit status screen
.
7.10 Liquid Temperature
Thermistor
(-)P20**B heat pumps are equipped with a
liquid termperature thermistor for the purpose
of measuring the liquid line temperature at the
outdoor unit. The liquid line temperature is used
by the VSODC to calculate the cooling and
heating mode liquid subcooling level. The VSODC
communicates the liquid line temperature and
subcooling level to the EcoNet™ Control Center
where they are displayed on outdoor unit status
screen
.
7.11 Outdoor Ambient
Temperature Sensor
The outdoor ambient temperature is sensed by a
thermistor located directly underneath the control
box where it is shielded from direct sunlight. The
thermistor leads plug into the connector marked
OAT on the Variable Speed Outdoor Control
(VSODC). The outdoor ambient temperature
is utilized by the VSODC and EcoNet
TM
Control
Center for several control functions and is
displayed on the EcoNet
TM
Control Center
.
7.12 Outdoor Fan Motor
All (-)P20 heat pumps are equipped with variable
speed outdoor fans controlled by a pulse width
modulated signal (PWM) from the Variable Speed
Outdoor Control. The fan speed is selected to
optimize performance based on compressor speed.
7.13 Outdoor Fan Blade
All (-)P20 heat pumps are equipped with a swept
fan blade design that provides improved efficiency
and quieter operation than conventional fan blade
designs
.
7.14 Power Inverter
Compressor Control
(-)P20 heat pumps are equipped with a power
inverter that varies the compressor speed to
match the changing capacity needs of the con-
ditioned space. The inverter interfaces with the
Variable Speed Outdoor Control (VSODC) which
communicates the level of system capacity that
is required to the inverter based on input from the
EcoNet
TM
Control Center or conventional 24VAC
2-stage thermostat. The inverter converts incom-
ing single phase power to simulated variable fre-
quency 3-phase power that is connected to the
3-phase compressor motor. Each of the four (-)
P20 models have unique inverter models spe-
cifically designed and qualified for that specific
model to provide reliable operation under the most
extreme conditions. Each inverter is programmed
to monitor compressor power consumption, motor
torque, input current, input voltage, compressor
discharge pressure, and compressor discharge
temperature. When the inverter identifies a con-
dition that could potentially result in compressor
or inverter damage, it automatically reduces the
compressor speed until a more reliable operat-
ing condition is obtained or shuts the compressor
completely off if necessary. Once safe operating
conditions are attained, the inverter will gradually
increase the compressor speed in an attempt to
Components
UNIT LOW CHARGE MODE MAX LOW CHARGE MODE MAX
RP2024B 1600
3000
3500 1800
3000
5500
RP2036B 1600
2800
3200 1800
2800
5700
RP2048B 1400
3750
4500 1800
3750
6500
RP2060B 1500
4100
5500 2000
4100
6500
COOLING
HEATING
RP20**B COMPRESSOR OPERATING SPEEDS
