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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
minimum flow resistance can significantly reduce
evacuation time.
N N o o t t e e : :
•
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.
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.
94
94. Close Valves B
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. 95
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.
Figure 47. Typical vacuum pump hookup
illustrates three
SCXF-SVX01Q-EN
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