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28
D - Refrigeration System
WARNING
R-134a systems are particularly susceptible
to moisture contamination which can only
be prevented by evacuating the system for a
minimum of 30 minutes to attain a minimum
29.9 inch (500 micron or lower) vacuum.
Evacuating System
To achieve the required levels of evacuation, a
properly maintained two stage vacuum pump in
good condition is required. It is absolutely essential
to maintain your vacuum pump according to the
manufacturer's instructions including required
oil changes at the recommended intervals.
Vacuum pump oil should always be changed after
evacuating a contaminated system.
Vacuum pump performance should be checked
periodically with a micron gauge.
1.
Make certain that charging cylinder valve,
hand shut-off valve, and manifold gauge
valves are closed.
2.
Start vacuum pump.
3.
Open hand shut-off valve and slowly
open both manifold valves, turning
counterclockwise, for two full rotations.
CAUTION
If high vacuum equipment is used, just
crack both manifold valves for a few minutes
and then open slowly for the two full turns
counterclockwise. This will prevent the
compressor oil from foaming and being drawn
into the vacuum pump.
4.
Operate the vacuum pump for a minimum
of 30 minutes to a minimum of 29.9" (500
micron) vacuum.
5.
Close hand shut-off valve to vacuum pump.
Watch compound gauge for several minutes.
If reading rises, there is a leak in the system,
go to step 6. If no leak is indicated, stop
vacuum pump. System is now ready for
charging.
6.
If a leak is indicated, stop vacuum pump and
introduce a small charge of refrigerant into
system by cracking valve on bottom of
charging cylinder until system is pressurized
to 40 or 50 lbs psig.
7.
Leak test low-side. Close compound gauge.
Run compressor for a few minutes and leak
test high-side. When leak is found, recapture
refrigerant using EPA approved recovery
system Repair and go back to step 1.
Charging The System
CAUTION
Check the serial plate for the correct
refrigerant type. It is extremely important to
verify the type of refrigerant in the system
before starting any sealed system repairs.
After charging the system with liquid be
certain to wait at least 5 minutes before
starting the compressor to give the refrigerant
a chance to disperse throughout the system.
Otherwise the compressor could be damaged
by attempting to pump excessive quantities
of liquid.
Preparing The Charging Cylinder:
1.
Make certain that hand shut-off valve to
vacuum pump is closed.
2.
Close high-side manifold gauge valve.
3.
Set charging cylinder scale to pressure
indicated on cylinder pressure gauge.
4.
Observe refrigerant level in sight glass.
Subtract amount to be charged into system
and note shut off point.
5.
Open charging cylinder valve slowly and
allow proper charge to enter system.
6.
As soon as refrigerant in sight glass has
gone down to predetermined level, close
charging cylinder valve.
WARNING
Disconnect the charging cylinder heater at
this time to prevent the cylinder pressure from
exceeding its maximum limits.
7.
Allow system to sit for five minutes.
8.
Turn on refrigerator compressor. Run
compressor for a few minutes and monitor
system pressures.
9.
When satisfied that the unit is operating
correctly, clamp the high-side process tube
with the pinch-off tool while the unit is still
running.
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