------------
Rolls-Royce
&
Bentley-------
Air
Conditioning
System
Manuol
Pressure-Saturation
Temperature
Relationship
1
Table -
Freon
12.
Pressure
Temperature
lb./eq.h>..
•F.
20
19.5
21
21
22
22
23
23.5
24
24.5
25
25.5
26 27
27
28.5
28
29.5
29
31
30
32.5
JI
33.5
32
34.5
33
36
34 37
35 38
the refrigerant
in
the system to be discharged to
atmosphere.
Care
must
be
taken
not
to
reiease
the refrigerant too quickly as this will result in oil
being drawn from the system.
The
operation
should
require
at
least
fifteen minutes
to
ensure
complete discharge.
Always use
two
spanners
in
opposition
when
releasing
and
securing flared connections, to
prevent damaging the flares
or
tubes.
On
completion
of
repair work it is necessary to
evacuate
and
sweep the system to remove all
moisture before re-charging. The compressor oil
level
should
be
checked, as described under
'Compressor'.
TO EVACUATE THE SYSTEM
The
use
of
a
vacuum
pump
for
evacuation
is
advisable
but
if
this is
not
available
the
com-
pressor may
be
utilised as
follows:-
Fit
the
manifold
gauge set to
the
compressor
as illustrated in Figure
17.
Forward-seat the com-
pressor
high pressure service valve
by
turning
it
clockwise to the
end
of
its travel.
Open
the
pressure valve
of
the manifold gauge set by
turning
it
fully anti-clockwise.
Press11re
Temperature
lb.leq.io.
"F.
36
39
37
40
38
41
39
42
40
43.5
41
44.S
42
45.5
43
46.S
44
47.5
45
48.5
46
49.5
47
50.5
48
51.S
49
52.25
50
53
Close the vacuum valve
of
the manifold gauge
set
by
turning
it clockwise.
Just
'crack'
the
low
pressure service valve
by
rotating it
one
half
tum
clockwise.
Start
the engine
and
switch
on
the blower
motors to
'Fast'
speed. Observe the vacuum
gauge
and
when a vacuum
of
28
inches Hg
is
reached, allow the compressor to continue drawing
a vacuum for a further 10 minutes, then switch off
the
system
and
close
the
pressure
valve
on
the
manifold gauge set. These two operations must
be
carried
out
simultaneously, necessitating two
operators.
Switch off the ignition
and
allow
20
minutes for
conditions to settle before taking a reading
of
the
vacuum
gauge.
This
reading
should
be
main-
tained for
5 hours.
If
a drop in vacuum is evident
after this period, a leak in the system is indicated
(see
under
leak detection).
TO
SWEEP
THE SYSTEM
Back-seat
the
high
pressure
service valve
by
turning
it fully anti-clockwise. Forward-seat the
low pressure service valve by turning it clock-
wise.
Connect
the
centre
union
of
the manifold
gauge
set
to
a
Freon
12
container.
Close
both
valves
on
the manifold gauge set by turning them
clockwise.
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