40
4.14.2 Diagnosing Expansion valves
NOTE:
Perform low side pump down, compressor
capacity test, controlled refrigerant level check, etc.
Repair as needed before continuing.
Symptoms may include
•
Not cooling efficiently with correct
refrigerant charge and properly
operating compressor
•
Frosting of expansion valve and further
to evaporator unsatisfactory with
proper defrost operations.
Check refrigerant charge, compressor function and all
other valves operations (Follow 4.8, 4.7, 4.12)
Check TXV bulb placement under insulation If unable
to adjust superheat.
Check For any blockage in TXV screen (located inside
the inlet orifice), and equalizer line. If good replace
TXV valve.
Causes of blockages can be caused by air
contamination. (Air and pressure create carbon
buildup)
Correct position of TXV bulb of z120 is 2 o’clock
.
4.14.3 Replacing expansion valve
k.
Remove refrigerant charge
l.
Remove insulation from expansion
valve bulb and then remove bulb from
suction line.
m.
Loosen flare nut and
disconnect equalizer line from
expansion valve.
n.
The TXV bulb is located below the center
of the suction line. This area must be
clean to ensure positive bulb contact.
Strap bulb to suction line and insulate
both.
o.
Install the equalizer tubes to expansion
valve.
p.
Evacuate, dehydrate and recharge unit.
q.
Check superheat (4.14.1).
4.15 ADJUSTING THE CPR VALVE
The CPR valve is fitted in the suction line ahead of the
compressor. The CPR protects the compressor against
overload during start-up after long standstill periods or
after defrost period (high-pressure in the evaporator)
The CPR valve is not factory pre-set and needs
adjustment AFTER replacement.
1.
Protective Cap
2.
Setting screw
3.
Main spring
4.
Stainless Steel Equalizer
5.
Throttling Assembly
Figure 24 - Correct TXV Bulb placement
Figure 25 - CPR Valve Components
