SERVICING
15
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 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 high vacuum hoses, micron gauge and charging
cylinder as shown.
2. Start the vacuum pump and open the shut off valve to
the high vacuum gauge manifold only. After the com-
pound gauge (low side) has dropped to approximately
29 inches of vacuum, open the valve to the vacuum
micron gauge. See that the vacuum pump will blank-off
to a maximum of 500 microns. A vacuum pump can only
produce a good vacuum if its oil is non-contaminated.
LOW SIDE
GAUGE
AND VALVE
HIGH SIDE
GAUGE
AND VALVE
TO
UNIT SERVICE
VALVE PORTS
VACUUM PUMP
VACUUM PUMP
ADAPTER
800 PSI
RATED
HOSES
CHARGING
CYLINDER
AND SCALE
EVACUATION
3. If the vacuum pump is working properly, close the valve
to the micron gauge and open the high and low side
valves to the high vacuum manifold set. With the valve
on the charging cylinder closed, open the manifold valve
to the cylinder.
4. Evacuate the system to at least 29 inches gauge before
opening valve to micron gauge.
5. Continue to evacuate to a maximum of 500 microns.
Close valve to vacuum pump and watch rate of rise. If
vacuum does not rise above 500 microns in three to five
minutes, system can be considered properly evacuated.
6. If micron gauge continues to rise and levels off at about