R408 causing blocked drier?

[Drew]

We converted an old R502 low temp freezer to R408 and since then we have had issues with the single core drier blocking up with fine brown dust? We have been forced to change it weekly and the quantity of the dust seems to be getting worse? Does the 408 clean up the system causing this dust to block up the drier?

[desA]

Three thoughts:

1. Is the filter-drier breaking down internally?
2. Is this a corrosion deposit eg. rust, coming off some parts?
3. How well did you flush during the conversion?

[Drew]

The drier physically is good.

There was no flushing. It was a room that could not be shut down for too long. It had a leak which was repaired and 408 was dropped in.

It looks like fine brown dust.

[desA]

Source: Bitzer Refrigeration Report - 15. Edition - A-501-15
Section: ...substitutes for R502

Page 15

Due to the good solubility characteristics of R22 and R290 an increased danger exists, that after conversion of the plant, possible deposits of oil decomposition products containing chlorine may be dissolved and find their way into the compressor and regulating devices.

Page 16

Before conversion generously dimensioned suction gas filters and liquid line driers should therefore be fitted for cleaning and after approximately 100 hours operation an oil change should be made; further checks are recommended.

[Drew]

Thanks DesA

Thats a good find!

[desA]

^ It's a pleasure...