Need technical help for -80 Deep freezer

[shinu]

We have designed Deep freezer using cascade system. Primary uses R 404 and secondary uses R 23 . After 2-3 Months working temperature increases tp -55 degrees. What will be the problem. Pls advise.

[rizwankhan]

couple, you used refrigerant both together R 404 & R 23 ? quote head pressure,suction pressure, fixed txv or capilary tube

[NoNickName]

What is tp? Evaporating temperature of the low stage?
How is the system? DX? Pumped liquid?

[D.D.KORANNE]

Look for the oil build up in low side r-23 evaporator . Probably you are operating at say -60 deg c or so the critical issue is the oil return . Although you would have used oil separators for r-23 , these are 80-85% efficient. Hence the oil carried over forms a film inside low side evap and efficiency drops . Another area is the quality of oil with r-23 ,it has to have a pour point lower than the design evap temp ( for r-23) . The oil solidifies and fails to return to compressor. For efficient oil return use of borosilicate microfibre with an efficiency of 99.999% would address the oil issue .

[D.D.KORANNE]

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[R. skiffington]

Probable case of oil logging, significant ice build up in freezer? leave off for a couple of days and restart. How old is the system? has it had other problems? Has it been operating 2-3 months from new? Hard to work with such little info.