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7.0 COMPONENTS & CONTROLS
7.10 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].
7.11 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
Center for several control functions and is
displayed on the EcoNet
7.12 Outdoor Fan Motor
All (-)P17 heat pumps are equipped with single-
speed PSC fan motors.
7.13 Outdoor Fan Blade
All (-)P17 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
(-)P17 heat pumps are equipped with a power
inverter that varies the compressor speed to match
the changing capacity needs of the conditioned
space. The inverter interfaces with the Variable
Speed Outdoor Control (VSODC) which communi-
cates the level of system capacity that is required
to the inverter based on input from the EcoNet
38
Control
TM
Control Center.
TM
TM
Control Center or conventional 24VAC 2-stage
thermostat. The inverter converts incoming sin-
gle phase power to simulated variable frequency
3-phase power that is connected to the 3-phase
compressor motor. Each of the four (-)P17 models
has a unique inverter specifically 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 condition that could poten-
tially result in compressor or inverter damage, it
automatically reduces the compressor speed until
a more reliable operating 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 meet the capacity demand
as long as the operating conditions remain within
the safe operating range of the compressor and
inverter.
1. High voltage input (L1 – Black; L2 – Yellow)
2. Ground connection
3. Choke Connection
4. High Pressure control connection (HPS) – with
automatic reset
5. Discharge line thermistor connection (Sensor)
6. Modbus communication connections (RS485)
7. Compressor connections (W-Black; V-Red;
U-Yellow)
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