Restrictions; Replacing The Txv - Traulsen G Series Service Manual

Reach-in & pass thru refrigerator & freezer

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test. Installing pressure test access valves should be the last resort. Superheat can be measured with two

thermometers securely attached to refrigerant lines. (T1) Measure the temperature at the inlet of the

evaporator coil after the TXV valve body. (T2) Measure the temperature at the outlet of the evaporator coil

after the TXV sensing bulb. Subtracting (T1) from (T2) will equal the superheat. The superheat should measure

somewhere between four to twelve degrees Fahrenheit.

6.5.5 Restrictions

If the flow of refrigerant becomes restricted at the TXV the valve will be very cold to the point of freezing, but

the evaporator coil will be warm with high superheat and subcooling. Both Low side and high side pressures

will drop. Although if refrigerant is added to the system the high side pressure will rise but the low side will

not.

If it becomes necessary to replace the TXV, care should be taken to replace it with the exact OEM part. When

brazing the TXV into the system care should be taken not to overheat the valve. This is best accomplished by

wrapping the valve with a cold wet rag. A dry nitrogen purge of 10 SCFH should be used to displace the oxygen

to prevent the creation of an oxidized film inside the piping which could lead to system contamination or a

restriction. Too much nitrogen pressure will blow back through the joint and cause pinholes. After replacing

the TXV be sure to pull a deep vacuum of 200 microns.

Figure 68: Measuring Superheat

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