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Figure 19. Fan sequence according to capacity.
OVERHEATING CONTROL STATUS
OPERATION
TXV Operation
The measurement of refrigerant flow to the evaporator is the
exclusive function of a TXV. It must measure this flow at precisely
the same rate at which the refrigerant is evaporated by the heat
charge.
The TXV does this by maintaining the coil with enough refrigerant
to maintain the correct superheat of the suction gas leaving the
evaporator coil.
The TXV regulates the flow in response to the superheat of the
charge.
If it is suspected that a TXV is not operating properly, checking
for overheating is the only way to be sure. Do this with precision
instrumentation to obtain meaningful results.
Operating overheat of 8°F to 12°F are considered normal. Here
are some "tips" to help in detecting and fixing performance
failures in a TXV:
• Check the bulb to make sure it is properly connected to
the suction line. If you can move the bulb manually, it is not
properly secured.
• The bulb must be perfectly insulated to protect it against the
effects of a draft.
• Check the equalizer line for restrictions (kinks) or signs of
frost. A frosted equalizer line indicates internal leaks and will
require valve replacement. Repair or replacement of a bent
equalizer will be necessary for the valve to operate properly.
TXVs are designed to measure liquid refrigerant flow. If the
refrigerant at the valve inlet contains flash gas, the valve capacity
will be reduced. Make sure
that the system is properly
charged and that there is some
subcooling at the valve inlet
before discarding the TXV.
iom-cliv-cf-eng
Dimensions (Mm)
Adjustable - ODF connections with 1/4" equalizer
Non-adjustable - Odf connections with 1/4" equalizer
Connections
A
3/8 ODF
41.9
1/2 ODF
41.9
5/8 ODF
54.6
7/8 ODF
54.6
1-1/8 ODF
61.0
EXV Operation
The electronic valve is intended for installation in refrigeration
circuits as an expansion device for the refrigerant fluid, using
the superheat calculated by means of a pressure probe and a
temperature probe, both installed at the evaporator outlet, as a
control signal.
An adequate subcooling of the fluid at the inlet is necessary to
prevent the valve from working in the presence of gas bubbles.
It is possible that the valve will increase its noise level if the
Refrigerant Charge is insufficient or if there are relevant water
charge losses upstream of the valve.
32
Circuit Functions
Dimensions
B
C
D
41.9
9.6 (3/8)
8.6
41.9
12.8 (1/2)
12.2
54.6
16.0 (5/8)
19.0
54.6
22.3 (7/8)
19.0
61.0
28.7 (1-
23.1
1/8)
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