5-9
62-11848
5.10.2
Replacing Valve Internal Parts
a. Remove the refrigerant charge. Refer to
b. Remove the coil snap cap, voltage cover and coil assembly. Remove the enclosing tube.
c. Check for foreign material in the valve body.
d. Check for a damaged plunger and o-ring. If the o-ring is to be replaced, always put refrigerant oil on o-rings
before installing.
CAUTION
!
Do not damage or over tighten the enclosing tube assembly. Place all parts in the enclosing
tube in proper sequence in order to avoid premature coil burn-out.
e. Tighten the enclosing tube.
f. Install the coil assembly, voltage cover and snap cap.
g. Evacuate, dehydrate and recharge the unit. Refer to
and
.
h. Start the unit and check operation.
Figure 5.6 Compressor Pressure Regulating Valve
5.11 ADJUSTING THE COMPRESSOR PRESSURE REGULATING VALVE (CPR)
The CPR valve is not factory pre-set and needs adjustment.
When adjusting the compressor pressure regulating valve (CPR) (refer to
), the unit must be running in
heating or defrost mode and at 2400 rpm (compressor speed). This will ensure a suction pressure above the
proper CPR setting. To adjust the CPR valve, proceed as follows:
a. Install a gauge on the suction line.
b. Remove cap from CPR valve.
c. With an 8 mm Allen wrench, loosen the jam nut.
d. Using the 8mm Allen wrench, adjust the set screw. To raise the suction pressure, turn the set screw clock-
wise; to lower the suction pressure, turn counterclockwise. Refer to
for CPR valve setting.
e. When the setting has been adjusted, tighten the jam nut securely against the set screw. This will prevent
any movement of the set screw due to vibrations in the unit. Replace the cap.
5.12 THERMOSTATIC EXPANSION VALVE
MOP expansion valve characteristics:
• Rule: in order to avoid compressor overcharge, a MOP expansion valve (with limited flow) is used.
• Operating: the expansion valve will not open more than the MOP setpoint. Any temperature increase at the bulb
should not open the expansion valve further. The thermal expansion valve is an automatic device which maintains
constant superheat of the refrigerant gas leaving the evaporator regardless of suction pressure. The valve func-
tions are: (a) automatic response of refrigerant flow to match the evaporator load and (b) prevention of liquid
refrigerant entering the compressor. Unless the valve is defective, it seldom requires any maintenance.
NOTE
Due to the time involved in adjusting the superheat, it is more economical to replace the valve rather
than to adjust it.
Cap
Jam Nut
S e t
Screw
