Leak Testing (Nitrogen Or Nitrogen-Traced); Evacuation - Daikin ComfortNet DX7TC Service Instructions Manual

SERVICING
S-101 LEAK TESTING (NITROGEN OR
NITROGEN-TRACED)
To avoid the risk of fire or explosion, never use oxygen, high pressure
air or flammable gases for leak testing of a refrigeration system.
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 op open at no more than 150 psig.
Pressure 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
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.
S-102 EVACUATION
REFRIGERANT UNDER PRESSURE!
Failure to follow proper procedures may cause property damage,
personal injury or death.
Do not front seat the service valve(s) with the compressor open, with
the suction line of the compressor closed or severely restricted.
IMPORTANT NOTE: Because of the potential damage to
compressors, do not allow suction pressure at service valve to drop
below 20 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 procedure.
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 high vacuum pump, capable of
producing a vacuum equivalent to 250 microns or less and
a vacuum gauge to give a true reading of the vacuum in the
system.
92
WARNING
WARNING
WARNING
WARNING
NOTE: Never use the Scroll compressor as a vacuum pump or run
when under a high vacuum. Motor damage could occur.
Condensing unit liquid and suction valves are closed to contain
the charge within the unit. The unit is shipped with the valve
stems closed and caps installed. Do not open valves until the
system is evacuated.
1. Connect the vacuum pump with 250 micron capability to
the service valves.
2. Evacuate the system to 250 microns or less using suction
and liquid service valves. Using both valves is necessary
as some compressors create a mechanical seal separating
the sides of the system.
3. Close pump valve and hold vacuum for 10 minutes.
Typically pressure will rise during this period.
4. If the pressure rises to 1000 microns or less and remains
steady the system is considered leak free; proceed to startup.
5. If pressure rises above 1000 microns but holds steady
below 2000 microns, moisture and/or non-condensables
may be present or the system may have a small leak.
6. Return to step 2: If the same result is encountered check
for leaks as previously indicated and repair as necessary
then repeat evacuation.
7. If pressure rises above 2000 microns, a leak is present.
Check for leaks as previously indicated and repair as
necessary then repeat evacuation.
LOW SIDE
GAUGE
AND VALVE
800 PSI
RATED
HOSES
TO
UNIT SERVICE
VALVE PORTS
VACUUM PUMP

EVACUATION

HIGH SIDE
GAUGE
AND VALVE
CHARGING
CYLINDER
AND SCALE
VACUUM PUMP
ADAPTER