Refrigeration Repair Practice; Leak Testing; Evacuation - Daikin DCH048 Series Service Instructions Manual

SERVICING
S-100 REFRIGERATION REPAIR PRACTICE
DANGER
Always remove the refrigerant charge in a proper
manner before applying heat to the system.
When repairing the refrigeration system:
WARNING
Disconnect ALL power before servicing.
1. Never open a system that is under vacuum. Air and
moisture will be drawn in.
2. Plug or cap all openings.
3. Remove all burrs and clean the brazing surfaces of the
tubing with sand cloth or paper. Brazing materials do not
flow well on oxidized or oily surfaces.
4. Clean the inside of all new tubing to remove oils and pipe
chips.
5. When brazing, sweep the tubing with dry nitrogen to
prevent the formation of oxides on the inside surfaces.
6. Complete any repair by replacing the liquid line drier in the
system, evacuate and charge.
BRAZING MATERIALS
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 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 150 psig.
30
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.
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 high vacuum pump, capable of producing a vacuum
equivalent to 25 microns absolute and a thermocouple
vacuum 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.
WARNING
Do not front seat the service valve(s) with the
compressor open, with the suction line of the
comprssor closed or severely restricted.
1. Connect the vacuum pump, vacuum tight manifold set
with high vacuum hoses, thermocouple vacuum 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 compound
gauge (low side) has dropped to approximately 29 inches
of vacuum, open the valve to the vacuum thermocouple
gauge. See that the vacuum pump will blank-off to a
maximum of 25 microns. A high vacuum pump can only
produce a good vacuum if its oil is non-contaminated.