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M M a a i i n n t t e e n n a a n n c c e e
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 any 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.
•
Rubber or synthetic hoses are not recommended
for system evacuation. They have moisture
absorbing characteristics that 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.
•
Install an electronic micron vacuum gauge in the
common line ahead of the vacuum pump shutoff
valve, as shown in
Figure 47, p.
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.
68
69. Close Valves B
N N O O T T I I C C E E
M M o o t t o o r r W W i i n n d d i i n n g g D D a a m m a a g g e e ! !
F F a a i i l l u u r r e e t t o o f f o o l l l l o o w w i i n n s s t t r r u u c c t t i i o o n n s s b b e e l l o o w w c c o o u u l l d d
r r e e s s u u l l t t i i n n c c o o m m p p r r e e s s s s o o r r m m o o t t o o r r w w i i n n d d i i n n g g d d a a m m a a g g e e . .
D D o o n n o o t t u u s s e e a a m m e e g g o o h h m m m m e e t t e e r r o o r r a a p p p p l l y y v v o o l l t t a a g g e e
g g r r e e a a t t e e r r t t h h a a n n 5 5 0 0 V V D D C C t t o o a a c c o o m m p p r r e e s s s s o o r r m m o o t t o o r r
w w i i n n d d i i n n g g w w h h i i l l e e i i t t i i s s u u n n d d e e r r a a d d e e e e p p v v a a c c u u u u m m . .
•
Open Valves B and C. Evacuate system to a
pressure of 300 microns or less. As vacuum is being
pulled on system, it may appear that no further
vacuum is being obtained, yet pressure is high. It is
recommended during evacuation process to
"break" vacuum to facilitate evacuation.
•
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.
N N o o t t e e : : 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 48, p. 69
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 vacuum with refrigerant and
complete the remaining Pre-Start procedures before
starting the unit.
illustrates three
PKG-SVX027C-EN
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