View Full Version : Low suction pressures on R422a

29-06-2014, 08:54 PM

We have started looking after a freezer ( -18 to -20'c) which l think was originally on R502 and has been converted to R408a and now too R422a.

The system is an air cooled recip plant with a fairly large receiver that feeds two coolers with thermal txv.

The power assemblies that are currently fitted are R22. We have tried the next size orifice up as the current one was slightly under size for the compressor but this has made no effect.

The system is still on mineral oil although we have added a small amount of POE to aid oil return as we were struggling with oil return and this seems to have helped.

All the high side figures seem ok, discharge pressure 16-18bar with 40k superheat and 6k subcooling on the liquid line, but the suction pressure is around 0.4 and 0.6 bar with 15-18' superheat what ever you do to the valve to decrease superheat.

I was hoping some of you may have some experience with R422a, and maybe shed some light on where we might be going wrong.

Thanks for any help.