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Fujitsu FO20R Series Installation Instructions Manual page 21

Variable speed r-410a heat pump outdoor units
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4.6 Initial Leak Testing
Indoor coils have only a holding charge of dry
nitrogen. Keep all tube ends sealed until
connections are to be made.
to purge lines or pressurize system for leak test.
Oxygen reacts violently with oil, which can cause
an explosion resulting in severe personal injury or
The variable speed inverter driven heat pumps
are equipped with an EXV and must be matched
to indoor coils or air-handlers that are also
equipped with EXVs. During shipment, vibration
has been found to move the EXV stem valve to
a near closed position despite being set to a fully
open position in the factory. Prior to leak testing
it is recommended to apply power to the indoor
and outdoor units, making sure there is no call
for operation by disconnecting the digital control
center or thermostat. By doing this, the controls will
immediately close the EXV's followed immediately
by opening them to the wide open position,
permitting free flow of nitrogen through the system
during the brazing process.
• Pressurize line set and coil through service
fittings with dry nitrogen to 150 PSIG [1,034 kPa]
(maximum). Close nitrogen tank valve, let system
sit for at least
15 minutes, and check to see if the pressure has
dropped. If the pressure has dropped, check for
leaks at the line set braze joints with soap bubbles
and repair leak as necessary. Repeat pressure
test. If line set and coil hold pressure, proceed with
line set and coil evacuation (see Sections 4.7 and
4.8 for evacuation and final leak testing).
Do not use oxygen
• The vapor line must be insulated for its entire
length to prevent dripping (sweating) and prevent
performance losses. Closed-cell foam insulation
such as Armaflex and Rubatex
insulations for this purpose. Use 1/2" [12.7 mm]
minimum insulation thickness. Additional
insulation may be required for long runs. The
liquid line must be insulated in any unconditioned
space when long line sets are used and anytime
the liquid line is run through an attic due to hot
temperatures that occur there.
4.7 Evacuation
Evacuation is one of the most important parts of
the entire installation and service procedure. The
life and efficiency of the equipment is dependent
upon the thoroughness exercised by the
serviceman when evacuating air and moisture from
the system.
Air or nitrogen in the system increases condensing
temperature and pressure, resulting in increased
power consumption, erratic operation, and reduced
Moisture chemically reacts with the refrigerant
and oil to form corrosive acid which attacks the
compressor motor windings and internal parts and
which can result in compressor failure.
• After the system has been leak-checked and
proven sealed, connect the vacuum pump and
evacuate system to 500 microns and hold 500
microns or less for at least 15 minutes. The
vacuum pump must be connected to both the
high and low sides of the system by connecting
to the two pressure ports. Use the largest size
connections available since restrictive service
connections may lead to false readings because
of pressure drop through the fittings.
are satisfactory



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