S--101 Leak Testing; (Nitrogen Or Nitrogen-Traced); Evacuation - Daikin ComfortNet DX18TC Service Instructions Manual

SERVICING
NOTE: The use of a heat shield when brazing is recommended
to avoid burning the serial plate or the finish on the unit. Heat
trap or wet rags should be used to protect heat sensitive
components such as service valves and TXV valves.
Copper to Copper Joints - Sil-Fos used without flux (alloy
of 15% silver, 80% copper, and 5% phosphorous). Recom-
mended heat 1400°F.
Copper to Steel Joints - Silver Solder used without a flux
(alloy of 30% silver, 38% copper, 32% zinc). Recommended
heat - 1200°F.
S--101 LEAK TESTING (NITROGEN OR NITRO-
GEN-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 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
WARNING
REFRIGERANT UNDER PRESSURE!
Failure to follow proper procedures may cause
property damage, personal injury or death.
WARNING
Do not front seat the service valve(s) with the
compressor open, with the suction line of the
comprssor 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.
78
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 pres-
sure, resulting in increased power input and reduced perfor-
mance. Moisture chemically reacts with the refrigerant oil to
form corrosive acids. These acids attack motor windings and
parts, causing breakdown. The equipment required to thor-
oughly 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.
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 capabil-
ity 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 me-
chanical 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-
condensibles 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
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.
indicated and repair