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Fujitsu FO20R Series Installation Instructions Manual page 27

Variable speed r-410a heat pump outdoor units
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5.7 Indoor Air-Flow
Correct indoor air-flow and proper supply air
distribution is critical to system comfort, efficiency
and reliability. Excessive indoor air-flow results in
elevated humidity levels in the cooling mode and
excessive air noise. Low indoor air-flow reduces
system capacity and can result in coil icing and
compressor failure in the cooling mode and can
cause nuisance high pressure switch tripping
and increases power consumption in the heating
Fortunately, when the 20 SEER heat pumps are
matched to the correct air-handler or furnace/
coil combination and are controlled by the
communication Digital Control Center, the
indoor air-flow is automatically controlled to the
proper level based on the model data stored
in the VSODC memory card. When the indoor
blower is operating, the Digital Control Center
5.8 Refrigerant Charging
The refrigerant charge for all systems should be
checked against the Charging Chart located inside
the access panel cover.
compressor shell is hot. Touching the compressor top
may result in serious personal injury.
approximately 60% higher (1.6 times) than R-22
pressures. Use appropriate care when using this
refrigerant. Failure to exercise care may result in
equipment damage or personal injury.
Charge for all systems should be checked against
the Charging Chart inside the access panel cover.
compressor without charge in the system.
Addition of R-410A will raise high-side pressures
(liquid and discharge).
System maintenance is to be
performed by a qualified and certified technician.
The top of the scroll
R-410A pressures are
Do not operate the
will display the indoor CFM in the Service Menu
of the control. The approximate CFM is also
displayed in 100 CFM increments by a flashing
LED on the air-handler or furnace control board
while the blower is operating (one flash per 100
CFM) for installations where a conventional 24VAC
thermostat is used.
Once the system is operating in the Charging
Mode, confirm the indoor CFM is close to those
values in the table below. If the displayed CFM
is not reasonable close to the value in the table,
confirm cooling dehumidification is disabled,
the indoor air-flow trim adjustment is set to 0%,
and verify the model numbers of the indoor and
outdoor units are an approved combination by
the manufacturer. Once the indoor air-flow is
verified, the indoor air-flow trim adjustment may
be changed to suit the installation and should be
done prior to final charge adjustment.
NOTICE: AHRI rated CFM may differ slightly from
values in the table below.
The optimum refrigerant charge for any outdoor unit
matched with an indoor coil/air handler is affected by
the application. Therefore, charging data has been
developed to assist the field technician in optimizing
the charge for all mounting configurations (UF –
Upflow, DF – Downflow, LH – Left-Hand Discharge,
and RH – Right-Hand Discharge). Refer to the
charging chart inside the access panel cover on
the unit and choose the appropriate column for the
specific application being installed or serviced. New
installations utilizing either an indoor coil installed on
a gas furnace or an air handler in the downflow or
horizontal right-hand discharge may require removal
of some refrigerant since the factory charge could
result in an overcharge condition for short line length
The following method is used for charging systems
in the cooling and heating mode. All steps listed
should be performed to ensure proper charge has
been set. For measuring pressures, the service
valve port on the liquid valve (small valve) and the
true service port located between the two service
valves are to be used.


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