GVZC20 Service Manual
SERVICING
21
of 15% silver, 80% copper, and 5% phosphorous). Recom-
mended heat 1400°F.
Copper to Steel Joints - Silver Solder used without a ux
(alloy of 30% silver, 38% copper, 32% zinc). Recommend-
ed heat - 1200°F.
LEAK TESTING
Leak test the system using dry nitrogen and soapy water
to locate leaks. If you wish to use a leak detector, charge
the system to 10 psi using the appropriate refrigerant then
use nitrogen to nish charging the system to minimum 150
PSIG 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.
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 eciency 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 nirtogen.
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, exacuate the system until it is below 500 microns
and hold for 60 minutes.
1. Connect the vacuum pump, vacuum tight manifold set
with vacuum hoses, micron gauge and charging cylinder
as shown.
2. Start the vacuum pump and open the shut o valve to
the vacuum gauge manifold only. After the compound