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jakb21599
01-01-2011, 10:15 PM
Hello, I have few questions about a freezer display case in a grocery store that hopefully you guys can help me with.
I noticed that the 1/2 liquid line filter has a 5 to 6 degree temperature drop across the filter using a pipe temperature clamp. (Their are no service ports on it to get a pressure drop) Is this with in range ? what is allowable for a temperature drop across them? What are some of the effects of this filter that it will cause on the system if it is stopped partly stopped up? thanks for your help

chilliwilly
01-01-2011, 10:33 PM
One degree C is around acceptable, getting towards three deg C, and the dryer needs changing.

DrFreezeMD
01-01-2011, 11:02 PM
Agree with ChilliWilly, That drier is partially clogged and time for changing. It may not a have a noticeable effect on system operation yet. A drier with a great pressure drop will actually frost on the body and cause High Superheat at that Evaporator Coil and the case will operate too warm.:cool:

jakb21599
02-01-2011, 12:15 AM
How do you know if the TEV/TXV on the case evaporator has got trash in it ? What are some ways i can find this out with out pulling down the system and taking apart to check it ? Are their certain signs that would lead you to a clogged valve?

750 Valve
02-01-2011, 02:02 AM
High superheat at the valve and no response to adjustments would indicate a blocked strainer at the TXV.

Pump the system down, change the drier, open up the TXV and visually inspect the condition of the TXV strainer. It's not a big job at all.

chilliwilly
02-01-2011, 12:28 PM
You will also hear a slight hissing sound from the TXV.

jakb21599
02-01-2011, 09:15 PM
I was told that the body of the txv valve should not be frosted or iced up. Is this true? This freezer has 2 of them and both are near about iced up. What would cause this if it is true about should not have ice or frost built up on the valve.

mikeref
03-01-2011, 10:59 PM
I was told that the body of the txv valve should not be frosted or iced up. Is this true? This freezer has 2 of them and both are near about iced up. What would cause this if it is true about should not have ice or frost built up on the valve.
If i were you, i would hop to it and change the drier before cabinet looses temperature. Follow 750 valve's proceedure and see how freezer runs after that.. Mike.

DrFreezeMD
04-01-2011, 04:43 AM
You can bet on this. If the Drier is Partially clogged the Strainer in the TXV is probably dirty as well. In the field, I have seen a partial carbon build up. Especially, If the Refrigeration Company that sealed the system wasn't careful with the brazing. Supermarket systems have many sealed joints:rolleyes:

Magoo
04-01-2011, 08:07 PM
Under sized liquid lines and too long liquid lines can also create same conditions a drier and TXV.
Install a sight glass and service ports at txv after changing drier.

DCoker
14-01-2011, 04:10 AM
How do you know if the TEV/TXV on the case evaporator has got trash in it ? What are some ways i can find this out with out pulling down the system and taking apart to check it ? Are their certain signs that would lead you to a clogged valve?
Your super heat will be higher than normal.

DCoker
14-01-2011, 04:22 AM
I was told that the body of the txv valve should not be frosted or iced up. Is this true? This freezer has 2 of them and both are near about iced up. What would cause this if it is true about should not have ice or frost built up on the valve.
Depends if there is a distributor past the TXV. Then no there shouldn't be any frost on the valve, if there is frost or ice on the valve body then there is a restriction in the valve. Clean the screen. If the screen on the valve is clean then u might have moisture in the system. Try pouring hot water on it about two gallons or so. If that doesn't work replace the TXV.