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Fujitsu FO20R Series Installation Instructions Manual page 22

Variable speed r-410a heat pump outdoor units
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• After adequate evacuation, open both service
valves by removing both brass service valve caps
with an adjustable wrench. Insert a 3/16" [5 mm]
or 5/16" [8 mm] hex wrench into the stem and
turn counterclockwise until the wrench stops.
• If not already connected from evacuation process,
gauges must be connected at this point to check
and adjust charge.
(especially scroll type) should never be used to
evacuate the air conditioning system because
internal electrical arcing in near vacuum conditions
may result in a damaged or failed compressor.
Never run a scroll compressor while the system is
in a vacuum or compressor failure will occur.
4.8 Final Leak Testing
After the unit has been properly evacuated and
service valves opened, a halogen leak detector
should be used to detect leaks in the system. All
joints and piping within the outdoor unit, indoor coil,
and interconnecting tubing should be checked for
leaks. If a leak is detected, the refrigerant should
be recovered before repairing the leak. The Clean
Air Act prohibits releasing refrigerant into the
4.9 Control Wiring
at the fuse box or service panel before making any
electrical connections. Also, the ground connection
must be completed before making line voltage
connections. Failure to do so can result in electrical
shock, severe personal injury, or death.
Turn off electric power
4.9.1 Digital Communications
The 20 SEER heat pumps are specifically designed
to be matched with and communicating air-handler
or gas furnace and the Digital Control Center.
While they are also designed to be controlled
by a conventional 24VAC 2-stage thermostat,
many features and benefits are lost. Therefore,
a conventional 24VAC 2-stage thermostat should
only be used in temporary emergency situations
until communication issues with the communicating
control system are resolved.
4.9.2 Digital Control Center
The Digital Control Center should be mounted 4 to
5 feet above the floor on an inside wall of the living
room or a hallway that has good air circulation
from the other rooms being controlled by the
Control Center. It is essential that there be free
air circulation at the location of the same average
temperature as other rooms being controlled.
Movement of air should not be obstructed by
furniture, doors, draperies, etc. The Control Center
should not be mounted where it will be affected
by drafts, hot or cold water pipes or air ducts in
walls, radiant heat from fireplace, lamps, the sun,
T.V. or an outside wall. See instructions packaged
with Control Center for detailed mounting and
installation instructions.
4.9.3 Digital Communication
Wiring Connections
The four 18 AWG low-voltage control wires must
be installed from the Digital Control Center to the
indoor unit and from the indoor unit to the outdoor
unit. The wire length between the Control Center
and indoor unit should not be greater than 100 feet
[30.5 m].
The wire length between the indoor unit and
outdoor unit should not be greater than 125 feet
[38.1 m].
Running low-voltage wires in conduit with line
voltage power wires is not recommended. Low-
voltage wiring must be connected to the low
voltage terminal block on the Variable Speed
Outdoor Control. The terminal block can be
unplugged from the control board to facilitate
A communicating heat pump system consists of
these matched components:
• Communicating heat pump outdoor unit.
• Communicating air handler or communicating
• Digital Control Center.



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