Unit installation

Maintenance
86 SCXF-SVX01K-EN
3. Make sure the inner and outer tubes of the joint are
symmetrical and have a close clearance, providing an
easy ‘slip’ fit. If the joint is too loose, the connection’s
tensile strength is significantly reduced. Ensure the
overlap distance is equal to the inner tube diameter.
4. Wrap each refrigerant line component with a wet cloth
to
keep it cool during brazing. Excessive heat can
damage the internal components.
Note: Use
40-45% silver brazing alloy (BAg-7 or BAg-28)
on dissimilar metals. Use BCup-6 brazing alloy on
copper-to-copper joints.
5. If using flux, apply it sparingly to the joint. Excess flux
will
contaminate the refrigerant system.
6. Apply heat evenly over the length and circumference
of
the joint.
7. Begin brazing when the joint is hot enough to melt the
brazing
rod.The hot copper tubing, not the flame,
should melt the rod.
8. Continue to apply heat evenly around the joint
circumference
until the brazing material is drawn into
the joint by capillary action, making a mechanically
sound and gas-tight connection.
9. Visually inspect the connection after brazing to locate
an
y pinholes or crevices in the joint. Use a mirror if
joint locations are difficult to see.
System Evacuation Procedures
Each refrigeration circuit must be evacuated before the
unit can be charged and started.
Use a rotary type vacuum pump capable of pulling a
vacuum of 100 microns or less.
Verify that the unit disconnect switch and the system
control circuit switches are “OFF”.
Oil in the vacuum pump should be changed each time the
pump is used with high quality vacuum pump oil. Before
using any oil, check the oil container for discoloration
which usually indicates moisture in the oil and/or water
droplets. Moisture in the oil adds to what the pump has to
remove from the system, making the pump inefficient.
When connecting vacuum pump to refrigeration system, it
is important to manifold vacuum pump to both high and
low side of system (liquid line access valve and suction
line access valve). Follow pump manufacturer’s directions
for proper methods of using vacuum pump.
Lines used to connect the pump to the system should be
copper and of the largest diameter that can practically be
used. Using larger line sizes with minimum flow resistance
can significantly reduce evacuation time.
Note: Rubber or synthetic hoses are not recommended
for system evacuation.They have moisture
absorbing characteristics which result in excessive
rates of evaporation, causing pressure rise during
standing vacuum test.This makes it impossible to
determine if system has a leak, excessive residual
moisture, or continual or high rate of pressure
increase due to hoses.
An electronic micron vacuum gauge should be installed in
the common line ahead of the vacuum pump shutoff valve,
as shown in Figure 50, p. 87. Close Valves B and C, and
open Valve A.
Start vacuum pump. After several minutes the gauge
reading will indicate the maximum vacuum the pump is
capable of pulling. Rotary pumps should produce
vacuums of 100 microns or less.
OpenValves B and C. Evacuate system to a pressure of 300
microns or less. As vacuum is being pulled on system,
there could be a time when it would appear that no further
vacuum is being obtained, yet pressure is high. It is
recommended that during evacuation process, vacuum be
“Broken”, to facilitate the evacuation process.
To break the vacuum, shut valves A, B, & C and connect a
refrigerant cylinder to charging port on manifold. Purge air
from hose. Raise standing vacuum pressure in system to
“zero” (0 psig) gauge pressure. Repeat process two or
three times during evacuation.
Note: It is unlawful to release refrigerant into the
atmosphere. When service procedures require
working with refrigerants, the service technician
must comply with all Federal, State, and local laws.
Standing Vacuum Test . Once 300 microns or less is
obtained, close Valve A and leave valves B and C open to
allow the vacuum gauge to read the actual system
pressure. Let system equalize for approximately 15
minutes.This is referred to as a “standing vacuum test”
where, time versus pressure rise. Maximum allowable rise
over a 15 minute period is 200 microns. If pressure rise is
greater than 200 microns but levels off to a constant value,
excessive moisture is present. If pressure steadily
continues to rise, a leak is indicated. Figure 51 illustrates
three possible results of “standing vacuum test”.
If a leak is encountered, repair the system and repeat the
evacuation process until the recommended vacuum is
obtained. Once the system has been evacuated, break the
NOTICE:
Valve Damage!
Remove, do not wrap, water cooled condenser
pressure relief valves during brazing. Failure to do so
could result in valve damage.
NOTICE:
Motor Winding Damage!
Do not use a megohm meter or apply voltage to a
compressor motor winding while it is under a vacuum.
Voltage sparkover could cause damage to the motor
windings.