R422d advice for a -21 freezer

[johnny cool]

Hi all, we have just retrofited two -21 freezers with r422d and are having problems with getting them below -16. suction pressures just below 1 bar and discharge pressure 13 to15 bar, ambeient inplant room 27 to 31 degrees c air on to condenser 17 to21c air off 27c. liquid line temp just after reciver 30 to 35 c . any help would be great thanks.:(

[B G Scott]

What was the original refrigerant?

[monkey spanners]

Is this an R22 retrofit?

What suction superheat is it running?

'just under a bar' is about -24c, i'm wondering if the txv is overfeeding the evaporator.
I think there is also a drop in capacity with a lot of the replacement refrigerants.

[johnny cool]

THANKS FOR YOUR REPLYS. The system was on r22. evaps are in the gods and the tev's are in the end panals so unable to get the superheat measurments easily. they did run ok for a few weeks but have just recently started playing up.

[johnny cool]

any body out there.

[monkey spanners]

I'm sure you will have checked this but there is often problems with 'o' rings failing after R22 is replaced, so shortage of refrigerant would be a thing i'd check for.

What make compressors are in the system? I have seen waxing problems of txvs after conversion, particularily with maneurops.

The other things to check are anything not refrigerant related, as its easy to get tunnel vision when something has been changed recently, compressors pumping ok, driers ok, defrost working ok, no air leaks into the rooms, temperature display acurate, etc.

Jon

[NoNickName]

Why are you guys playing with darn retrofits?
Don't touch R22. Don't fix it if it ain't broken.

[monkey spanners]

Have a look here, note a 20% capacity drop with R422D, maybe there isn't enough time in the day for it to keep up?


http://www.tecumsehcoolproducts.com/inside/File_attachments/Service%20Guidelines%20HCFC%20R22%20to%20HFC%20Blends-RD-0003-E.pdf

Pleanty of other useful info too!

Jon

[licencetochill]

Well said NONICKNAME!! Leave the bloody R22 alone.!

[johnny cool]

Thanks chaps for advice, turns out both systems short of gas. oh joy. thanks again you lot.