SERVICING
15
LEAK TESTING (NITROGEN OR NITROGEN-TRACED)
WARNING
To avoid the risk of fire or explosion, never use oxygen,
high pressure air or flammable gases for leak testing of a
refrigeration system.
WARNING
To avoid possible explosion, the line from the nitrogen
cylinder must include a pressure regulator and a pressure
relief valve. The pressure relief valve must be set to open at
no more than 450 PSIG.
Pressure test the system using dry nitrogen and soapy wa-
ter to locate leaks. If you wish to use a leak detector, charge
the system to 10 PSIG using the appropriate refrigerant
then use nitrogen to finish charging the system to working
pressure, then apply the detector to suspect areas. If leaks
are found, repair them. After repair, repeat the pressure
test. If no leaks exist, proceed to system evacuation.
STANDING PRESSURE TEST (RECOMMENDED)
Best practices dictate system should be pressure tested
at 450 PSIG with nitrogen for a minimum 4 hours. Follow
the procedure outlined below to test system. If leaks are
found, repair them. After repair, repeat the leak pressure
test described above. If no leaks exist, proceed to system
evacuation and charging.
SYSTEM PRESSURE TESTING
Once all of the refrigerant line connections are completed.
Perform a 3-step nitrogen pressure test.
1. Pressurize the system with nitrogen to 150 PSIG and
hold for 3 minutes. If any pressure drops occur, locate
and repair leaks and repeat step 1.
2. Pressurize the system with nitrogen to 325 PSIG and
hold for 5 minutes. If any pressure drops occur, locate
and repair leaks and repeat step 1.
3. Pressurize the system with nitrogen to 450 PSIG and
hold for 4 hours. If any pressure drops occur, locate
and repair leaks and repeat step 1.
EVACUATION
WARNING
REFRIGERANT UNDER PRESSURE!
Failure to follow proper procedures may cause property
damage, personal injury or death.
IMPORTANT NOTE:
Because of the potential damage to
compressors, do not allow suction pressure at service valve
to drop below 5 PSIG when pumping unit system down for
repair. Outdoor section, depending on line set length and
amount of charge in system, may not be able to hold the
entire system charge.
This is the most important part of the entire service proce-
dure. The life and efficiency of the equipment is dependent
upon the thoroughness exercised by the serviceman when
evacuating air (non-condensables) and moisture from the
system.
Air in a system causes high condensing temperature and
pressure, resulting in increased power input and reduced
performance.
Moisture chemically reacts with the refrigerant oil to form
corrosive acids. These acids attack motor windings and
parts, causing breakdown.
The equipment required to thoroughly evacuate the system
is a vacuum pump, capable of producing a vacuum equiva-
lent to 500 microns absolute and a micron gauge to give a
true reading of the vacuum in the system.
NOTE:
Never use the system compressor as a vacuum
pump or run when under a high vacuum. Motor damage
could occur.
The triple evacuation method is recommended.
1. Evacuate the system to 4000 microns and hold for 15
minutes. Then, break the vacuum with dry nitrogen,
bring the system pressure up to 2-3 PSIG, and hold
for 20 minutes. Release the nitrogen.
2. Evacuate to 1500 microns and hold for 20 minutes.
Break the vacuum with dry nitrogen again, bring the
system pressure back up to 2-3 PSIG, and hold for 20
minutes.
3. Then, evacuate the system until it is below 500 mi-
crons and hold for 60 minutes.
WARNING
Do not front seat the service valve(s) with the compressor
open, with the suction line of the compressor closed or
severely restricted.
1. Connect the vacuum pump, vacuum tight manifold set
with high vacuum hoses, micron gauge and charging
cylinder as shown.
