Advertisement
AIR CONDITIONING
24-21
to maintain
exactly
75
psi on the discharge gauge.
(4)
The suction gauge should register
60
to
70
psi
when pressure registered at the discharge gauge is
maintained at exactly
75
psi.
Minimum Flow Test-
Thermul Bulb ut
32°F
(1)
Close the right gauge valve to reduce pressure
on the expansion valve. This will accelerate move-
ment of the valve toward the "minimum flow" posi-
tion.
(2)
Insert the thermal bulb in the container of ice
and water. Use sufficient ice to insure a water tem-
perature of 32" F. This will cause the expansion valve
to move to the "minimum flow" position.
(3) Adjust the right gauge valve to maintain
ex-
actly
75
psi as registered at the discharge pressure
gauge.
(4)
The suction gauge should register
21
to
24
psi
when discharge pressure is maintained at exactly
75
psi.
Test Results and Corrections
If the expansion valve does not pass these tests,
it
must be replaced. For detailed instructions on expan-
sion valve replacement, refer to "Expansion Valve
Replacement."
An expansion valve which passes the above tests
has the proper super heat setting, the proper pressure
limit calibration, the correct rated capacity and has
not lost its thermal bulb charge. Therefore,
it
will
give satisfactory performance.
Since the system is without refrigerant,
it
is good
practice to remove the expansion valve inlet screen,
clean it if necessary and reinstall
it
before charging
the system. Clean the thermal bulb, the thermal bulb
well and the brass thermal bulb wedging strips.
Wedge the bulb into its well so that the brass strips
force the bulb toward the suction line. The fit must
be mechanically tight and all surfaces clean
to
insure
good thermal contact.
To put the system into operation
it
will be neces-
sary to sweep, test for leaks, vacuum and recharge
the system.
MAINTAIN EXACTLY 7 5 PSI
BY ADJUSTING VALVE
L BULB IN ICE WATER
0 70PSI THE
SP-2922
NY3
19B
Fig. 22-Expansion
Valve Test
Hide quick links:
Advertisement
