R422D Oil return problems !

[nike123]

Thanks all
However the information i have says 422D is suitable for medium and low temp , so im confused.
have also tried adding a small amount of poe oil , but still having problems with oil return .

im wondering if velocitys may be lower with this gas ?
as it has problems at low temp/low velocitys
or is it just purely miscibility ?

thanks

It is also said in document I posted that it could be used in low temperature refrigeration systems but in parentheses.

Applications

• Medium-temperature commercial and industrial DX refrigeration (can also be used for low temperature):
  
  • Food service
  • Supermarket display cases
  • Food storage and processing
  • Ice machines
  
  
• Residential and commercial air conditioning:
  
  • Best choice for DX water chillers
  
  

But significant is that R422A is declared as suitable for low refrigeration systems:

Applications

• Medium- and low-temperature commercial and industrial direct expansion refrigeration, including:
  
  • food service
  • supermarket display cases
  • food storage and processing
  • ice machines
  
  

So, it appears that R422D is not best solution for low temperature refrigeration.
Anyway, you should read this from R422D retrofit instructions:

7. Monitor oil levels. During initial operation of the system
it is very important to monitor the level of oil in the
compressor (or compressor oil management system)
to verify that oil is returning to the compressor in an
adequate manner.
• If the oil level falls below the minimum allowed level,
top up to the minimum level with the existing oil type.
Do not fill to the maximum level as the level may rise
again.
• Should the oil return appear to be erratic as evidenced
by large swings in oil level during the refrigeration
system cycle it is recommended that some of the oil
be removed from the system and replaced with POE
oil. Replacement of up to 25% of the oil with POE will
help to restore oil return stability. The exact amount
of oil to be changed will depend on the system itself
(evaporating temperatures, physical geometry, etc.)
• POE lubricant should be progressively added to the
system. An initial addition of 10% (of the total oil
charge) should be made. This should be followed by
5% increments until the oil level returns to normal.
• It is important to ensure that, when adding POE oil to
the system, the oil level (immediately after addition)
is kept below the system mid-point (e.g. mid-sight
glass) oil level.
8. Label the system to clearly and permanently show the
refrigerant in the system and any oil(s) present in the
system.