25
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.
WARNING:
Do not use oxygen
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
death.
•
Pressurize line set and coil through service fittings
with dry nitrogen to a maximum of 150 PSIG [1034
kPa]. 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).
• The suction 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
®
are satisfactory
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
capacity.
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.
IMPORTANT:
The outdoor units are shipped with
a nitrogen holding charge and must be evacuated
along with the line set and indoor coil.
After the system has been leak-checked and proven
leak free, open both outdoor unit service valves
and connect the vacuum pump to the hose from
the middle port of the manifold gauge set. Connect
the high and low side hoses to the service ports
on both service valves. Open both valves on the
gauge set completely before starting the vacuum
pump. Evacuate system to 500 microns and hold
500 microns or less for at least 15 minutes. Use the
largest size connections available since restrictive
service connections may lead to false readings
because of pressure drop through the fittings.
ST-A1226-180-00
ST-A1226-182-00
ST-A1226-181-00
4.0 INSTALLATION
NOTE:
Units shown in illustrations are generic
representations and may differ from the actual unit
being installed.
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