Vacuum Pump Maintenance; Vacuum Chart - Frigidaire FFBN1721TV0 Technical & Service Manual

Service Manual - Four-door Refrigerator ( FFBN1721TV0 )
Sealed System

Vacuum Pump Maintenance

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 periodi-
cally with a micron gauge.
Vacuum pump suppliers may or may not recommend changing
the vacuum pump oil to the same type that's in the system being
evacuated. Some manufacturers may recommend a vacuum
pump that's dedicated to R-134a systems.
Robinair has stated that their current and discontinued vacuum
pump models, using mineral oil currently specified for use in their
vacuum pumps, can be used to evacuate R-134a/Ester oil
systems.
For other brands of vacuum pumps, check with the manufacturer
for restrictions and guidelines when using with R-134a.
IF YOU USE A VACUUM PUMP WITH
MINERAL OIL TO EVACUATE AN R-134a
SYSTEM, IT IS ABSOLUTELY ESSENTIAL
TO HAVE A SHUT-OFF VALVE BETWEEN
PUMP AND YOUR MANIFOLD GAUGE
SET. THE HAND VALVE MUST BE CLOSED
DURING ALL TIMES WHEN VACUUM
PUMP IS NOT OPERATING. THIS WILL
PREVENT MIGRATION OF MINERAL OIL
VAPOR
CAUTION
SYSTEMS.
SHOULD STOP DURING EVACUATION
FOR ANY REASON, THE HAND PUMP
SHUT-OFF VALVE MUST BE CLOSED
IMMEDIATELY.
Page 34
INTO R-134a/ESTER
IF THE VACUUM PUMP

Vacuum Chart

Vacuum Inches Hg. Microns
28.940
29.530
29.832
29.882
29.901
29.915
29.917
29.919
To achieve the required 29.9 inch (500 micron) vacuum, a
properly maintained two-stage vacuum pump in good condition
is required.
A two stage pump can reach a deeper vacuum than a single
stage because the exhaust from the first pumping stage is
discharged into the second pumping stage.
This means the second stage begins pumping at a lower
pressure so a lower ultimate vacuum can be achieved.
OIL
Boiling Point of Water °F
25000 77.9
10000 52.0
4600 32.0
1000 1.0
500 -11.2
150 -32.8
100 -38.2
50 -49.0
Figure 8