freezer

dmy hvac

ive been working on a 2 door freezer it leaked all the freon out originally.had a rub through on the high side i repaired that and replaced filters leak checked and found very small leak on compressor terminals so then i replaced compressor fired unit up unit was r502 i converted to 408 pressures were running at 225 and 10 which i thought was not bad.but freezer ran for an hour and would not get below 20 degrees it has a cro valve on it so i opend it all the way head pressure dropped to 160 and suction went up to 60 i know they are used to prevent flood back to compressor after defrost is there any other use for them?how do you set them by amp draw on compressor after defrost?i will be replace expansion valve tomorow cause i could not get pressures to change with the txv all the way open or shut.there is no reciever or sight glass can i just open cro valve all the way and charge system by super heat and pressures?then adjust cro valve?any suggestions??

ddlong1286@yahoo.com

What Brand?

Hello,

What brand of CRO? I prefer Sporlan and you will find all the info you need to set theirs at their website, www.sporlan.com. Make sure you do not get a pressure limiting txv. It will duplicate the purpose of the CRO valve.

I have replaced the CRO valve with a pressure limiting txv. One less part to fail and keep track of. If you keep the cro and txv setup, you will need to have a pressure tap before and after the cro to properly adjust the cro valve.

Also remember, you should not adjust the txv till the box temp is close to the temp setting. By the way what brand is the unit?

Hope this helps!
Don in Mo

JackEnnisMartin

freezer

I have to assume by your letter you are not an oldtimer. The problem is you have done to many things and now you do not have a single place to branch off from. The rule of thumb in the refrigeration trade is you only touch the txv as a last resort in a problem job. I would suggest you do the following ;to get you back to a solid starting place.
Remove the refrigerant in the system.Install a sight glass on the unit -- it was charged at the factory with a scale and they did not require a sight glass. Put the system under a low vacumn for at least one hour. Return all the system devices as close to factory as you can. Now charge the unit into the reciever if you can and if not ;charge the unit slowly. Let the machine run for an hour and then check the compressor superheat. On freezers this is the most important reading of all. The superheat should be at least 20 degrees to a max. of 35 depending on the system type. Now ,if you have the problems again start to check what is going on in a step by step way and do not let anyone hurry you. The most imporant tool you have after your gauges is your ampprobe. Put it on the compressor and read it constantly. The idea you have to get into your mind is the only problem with this machine before was a leak --- so it has to have something to do with the refrigerant and the way I have introduced it to the system. Good luck and one more word --- low temperature jobs take time --- you are rushing ,slow down.
Jack Ennis Martin