2 solid door reach-in freezer trouble

[jayryu]

I've got a service call to a reach-in freezer. The freezer keeps the temperature of abt. 40 ~ 45F and compressor run continually. The data is as under.
compressor : coplaweld FJAF-A056-IAA.
Refrigerants: R404a
Box temp: 46.5F
Low press.: 17 psig
Low side(compressor suction) temp: 69F
High press: 240 psig
High side temp(after receiver) : 99.3F
Condenser in/out air temp: 90/106F
suction superheat : 88F, subcool: 2.5F

Checked TXV with sensing bulb dipping warm and cold water and found suction pressure changes.
I have thought first it is shortage of refrigerants and charged about 2.0 lbs more.
But before and after the gas charge the operating data was not changed almost at all as above. I don't know what to do next.
I hope there will be some solution.

[jayryu]

Original refrigerants charge is 48 ounces. When I checked the freezer 1st time, suction superheat was 90F, subcool was 2F. After charging 32 oz more, superheat & subcool has not changed almost at all. I can't understand in my physics what 's happening.

[sedgy]

hi j , your fridge is overcharged your evap is too low psi , regards sedgy,
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[jayryu]

Thank you sedgy,
But before me nobody manipulated the freezer I think. Until 4 days ago it worked fine, but the temperature slowly creeeped up according to the owner. Before charging the gas by myself subcool was so low as 2 degree F. I thought low subcool means low charge. Superheat was so high as 90F in compressor suction side. It is a kind of mystery to me now. I doubted TXV first, but as I mentioned before It seems working properly.

[mikeref]

Sounds to me like TX is not feeding properly. 17 psi pressure when cabinet is a few degrees above 0*c or 32F is not right. Adding more gas just bumps up reciever level if suction pressure does not change. Sight glass will be clear so pump down and pop out the orifice first. Fit new one and if opperating conditions are the same, then toss the TX.. Mike.

[jayryu]

Thanks mikeref,
I did not try anything yet. As you suggested The TXV is continually gnawing my brain. I 'll check TXV next week.
But I still wondering why subcool is so low and almost no change happens when I charged 2.0lbs of gas more.

[Gary]

Most likely, the TXV inlet strainer is plugged. Less likely, the liquid line is kinked or the drier partially plugged.

Also, you have more subcooling than you think. Your SCT is 101F, but your leaving air temp is 106F. If the refrigerant is 101F, then how can the air temp be 106F? Where did the extra heat come from? Either the gauge is wrong or the thermometer is wrong.

[jayryu]

Hi Gary thanks for your fast reply and recommendation,
Gauge and thermometer is ok. I can't find any problem with the condenser outlet air temp was higher than SCT. The extra heat comes from very high compressor discharge gas temperature.

[jayryu]

Today, I have checked Txv inlet screen and found somewhat dirty but not clogged. I have replaced the TXV with new one and charged only 34 oz instead of 48 oz marked on name plate because of the sight glass cleared. And the freezer works fine now.
Thank you for all gentlemen who gave an attention to my post.