------------
Rolfs-Royce
&
Bentley-------
Air
Conditioning
System
Manual
4.
Discharge the refrigerant, remove the
discharge line, and inspect it for signs
of
restriction. Inspect the condenser
for
kinked
or
obstructed tubes; apply dry com-
pressed air
or
nitrogen to the tuhes to dis-
lodge obstructions or,
if
necessary, renew
the unit.
5.
Test the thermostats
and
solenoid valves
for correct operation, check the wiring con-
nections.
6.
Inspect the condenser matrix for obstruc-
tions and remove any foreign matter
by
cleaning the matrix with warm water and
applying compressed air from the side
adjacent to the radiator.
7.
Test the pressure-saturation temperature
relationship
of
the refrigerant (see Page
26).
Lo-w
suction
pressure
and
low
head
pressure
Possible causes:
l. Refrigerant charge low.
2.
Filter-drier unit obstructed.
3.
An obstruction in the liquid line.
4.
An incorrect expansion valve superheat
setting.
5.
A damaged temperature control phial
or
a
phial
not
correctly
in
contact
with its
adjacent pipe.
6.
An expansion valve filter
or
port plugged
with.
moisture or grit.
7.
Faulty compressor valves.
Action to be taken:
1.
Check the system for leaks
and
re-charge.
2.
Clean
the
filter
and
renew the dehydration
charge
or
renew the· complete unit.
3.
A partial blockage in the pipe will create a
temperature fall
at
the point
of
restriction;
this will be obvious
to
the touch. Remove
the pipe from the unit
and
remove the
obstruction, using dry compressed air or,
if
necessary,
fit
a new pipe.
4.
Check the superheat reading (see Page
26),
reset or,
if
necessary, renew the expansion
valve.
5.
Inspect the temperature control phials for
maximum contact with their adjacent pipes,
and
examine the phials
and
c·apillary tubes
for damage. Renew the complete valve
unit
if
damage prevents correct operation.
6.
Remove and clean the expansion valves and
filters.
7. Carry out the pressure test (see Page
15),
if
this reveals a faulty valve, renew the valve
plate assembly.
Low
suction
pressure
and
high
head
preuure
The
probable
cause
is
a blockage
in
the
discharge pipe
or
condenser tubes. The obstruc-
tion should be removed or,
if
necessary, the
component renewed.
High
suction
pressure
and
high
head
pressure
Probable causes are:
1.
The superheat setting
of
the expansion
valve
or
valves
is
too low, causing the
admission
of
liquid refrigerant to the
compressor.
2.
An obstructed condenser matrix.
3.
The presence
of
air
and/
or
moisture
in
the
system.
4.
Too great a quantity
of
refrigerant.
Action to be taken:
I. Test the expansion valves
and
adjust or,
if
necessary, renew a faulty valve.
2.
Wash the external surfaces
of
the condenser
matrix with warm water and free the matrix
of
obstructions by applying compressed air
to the face
of
the matrix adjacent to the
radiator.
3.
Discharge the system and re-charge it with
the correct quantity
of
refrigerant.
4.
Evacuate and re-charge the system.
Suction
pressure
correct
but
head
pressure
high
Probable causes are:
1.
The presence
of
air in the system.
2.
Too
great a charge
of
refrigerant.
Page25
To Next Page
Loading...
