INSTALLATION INSTRUCTIONS
R
−
410A Split System Heat Pumps
428 01 1703 01
13
Specifications subject to change without notice.
MAJOR COMPONENTS
2-Stage Control
The 2
−
stage control board controls the following functions:
— Compressor high and low stage operation
— Outdoor fan motor operation
— Compressor external protection
— Pressure switch monitoring
— Time delays
— Defrost Control
Field Connections
On models with non
−
communicating (Thermostat other than
Observer Wall Control) system, the 2
−
stage control receives
24vac low
−
voltage control system inputs through the Y1, and
Y2 connections located at the bottom of the control board
(see Fig. 14). The OD units can be controlled using a
standard 2-stage thermostat or Observer Wall Control.
2-Stage Compressor
The 2
−
stage compressor contains motor windings that
provide 2
−
pole (3500 RPM) operation. Refer to Table 4 for
correct winding resistance.
Compressor Internal Relief
The compressor is protected by an internal pressure relief
(IPR) which relieves discharge gas into compressor shell
when differential between suction and discharge pressures
exceeds 550
−
625 psig The compressor is also protected by
an internal overload attached to motor windings.
Compressor Control Contactor
The contactor has a 24 volt coil. The electronic control board
controls the operation of the appropriate contactor.
TEMPERATURE THERMISTORS
Thermistors are electronic devices which sense temperature.
As the temperature increases, the resistance decreases.
Thermistors are used to sense outdoor ambient (OAT) and
coil temperature (OCT). Refer to Fig. 15 for resistance values
versus temperature. If the outdoor ambient or coil thermistor
should fail, the control will flash the appropriate fault code
(see Table 6.)
IMPORTANT
:
Outdoor air thermistor and coil thermistor are
factory mounted in the final locations. Check to insure
thermistors are mounted properly per Fig.8 and Fig.9.
Thermistor Sensor Comparison
The control continuously monitors and compares the outdoor
air temperature sensor and outdoor coil temperature sensor
to ensure proper operating conditions. The comparison is:
— If the outdoor air sensor indicates 10
F (5.56
C) warmer
than the coil sensor (or) the outdoor air sensor indicates
20
F (11.1
C) cooler than the coil sensor, the sensors are
out of range.
— If the sensors are out of range, the control will flash the
appropriate fault code as shown in Table 6.
Failed Thermistor Default Operation
Factory defaults have been provided in the event of failure of
outdoor air thermistor and/or coil thermistor.
OAT Thermistor must be locked in place with
spherical nib end facing towards the front of
the control box.
Final Checks
IMPORTANT:
Before leaving job, be sure to do the following:
1. Ensure that all wiring is routed away from tubing and
sheet metal edges to prevent rub-- through or wire
pinching.
2. Ensure that all wiring and tubing is secure in unit
before adding panels and covers. Securely fasten all
panels and covers.
3. Tighten service valve stem caps to 1/12--turn past
finger tight.
4. Leave Owner’s Manual with owner. Explain system
operation and periodic maintenance requirements
outlined in manual.
Care and Maintenance
For continuing high performance and to maintain warranty
coverage, periodic maintenance must be performed on this
equipment. Frequency of maintenance may vary depending
upon geographic areas, such as coastal applications. See
Owner’s Manual for information.
