iom-clicsa-cf-eng
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27
Circuit Functions
OVERHEATING CONTROL STATUS 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 flow in response to charge superheat.
TXV Operation
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 leakage 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.
Dimensions (Mm)
Adjustable - ODF connections with 1/4” equalizer
Non-adjustable - Odf connections with 1/4” equalizer
Connections
Dimensions
A
B
C
D
3/8 ODF
41.9
41.9
9.6 (3/8)
8.6
1/2 ODF
41.9
41.9
12.8 (1/2)
12.2
5/8 ODF
54.6
54.6
16.0 (5/8)
19.0
7/8 ODF
54.6
54.6
22.3 (7/8)
19.0
1-1/8 ODF
61.0
61.0
28.7 (1-1/8)
23.1
