So Low Ultra low frezeer retrofit

First thing, I would like to introduce my self, becuase this is my first post on this thread, I am a Biomedical Engineering Technician who's working in Jakarta-Indonesia.
I have been involving in Ultra Low Cascade refrigeration since 1997, maintain and repair some ULT like Revco, Harris and So Low.
Now I am working on retrofitting So Low U85-22 from R22 Hidh Stage and R503 Low Stage to the new Refrigerant R404A for High Stage and R508B for Low Stage. I have been flushed the both system 3 times, changed the oil to POE and then charge base on refrigerant company bulletin but I found the problem this ULT freezer couldn't reach set point temperature.
Anybody could help me, if anybody have any experience retrofitting So Low ULT share with me,please...

Many Thanks,

hi there, the problem you will have possibly is the capillary lines as they might required to be changed for the retrofitting. i will have a look in my service manuals and get back to you with the capillary sizes and length and give that a try. for the oil i use as standard mobil eal arctic 22 it is a very good oil to use in the second stage. hope this helps

hi there, just had a look in my service manual, the 1st stage gas charge for r404a is 24oz, the 2nd stage gas charge depends on if you use r170 or r290 as the oil additive the gasmixs are as follows, the charge is from vacuum to 30psi(r170 or vacuum to 20psi(r290) then add r508b to 165psi. the capillary lines are high stage 17inches of .050, the low stage is 24inches of .050 but you must use the mobil arcti eal 22 oil. please let me know how you get on as i will probably have to do this job one day.

kindest regards graham.

Hi Graham..many thanks to your help and info, I'll tried and let you know.
Any suggestion if I also plan to changed for new compressors since the unit been worked for 17 years and only 1 breakdown in 1998 changed low stage compressor but still charged with R503, if you know any info for the replacement compressor from other brands because there's no So Low authorized dealer here.
Best regards,
Asep

hi asep, if you can not go to so-low in the usa, i always use an embraco j2192gk, it is tried and tested compressor and very reliable. if you need any more information on any make and model of ult freezer please email me direct on graham.hand@mirefrigeration.co.uk

kindest regards graham

hi Asep,

ive just realized that the measurements for the capillary lines i mentioned the length is not in inches but in feet, so the 1st stage is 17 feet long .050 the 2nd stage is 28 feet long .050 truely sorry about that mistake.

graham

Hi, Graham...I just rethinking about the cap.tube lenght why is too short.., then you also realized about that. Thanks also with compressor info.
Anyway, I really appreciated for your info which is very helpful for me. I'll contacted to your email when I need some more info. about others ULTs.

Regards,
Asep