Frozen accumulator

[Royal241]

5 hp semi-hermetic low temp walk in freezer, hot gas defrost, R-408. Replaced compressor over 1 year ago, after replacement I observed "milky oil in sight glass", closed expansion valve a bit, problem solved. After 6 months I inspected unit, same oil problem and suction line frozen ( evaporator clear) Installed an accumulator, seemed that the problem went away (this was winter season). Compressor is in a basement with a remote condenser. Spring is here and now the basement warmed up by around 10F to lets say 60F, think I should mention this. After a brief visit to the site I observed the accumulator frozen 3/4 up, suction frozen from the accumulator to the compressor valve but not frozen from the evaporator to the accumulator. What the hell am I missing? Is the equalizing line from the valve faulty? There is no crankcase heater ( I just bought one and will install in a few days just to gain some extra time b4 breakdown). This freezer was designed like 20 years ago and worked without major problems until 1.5 years ago. I serviced this unit for the last 10 years and now I'm lost. Thank you for any suggestions.

[RONB]

Is your hot gas valve slightly passing and allowing refrigerant to condense in the accumulator?If your evap is clear and the superheat is ok I would have a look at the HG Valve.

[chemi-cool]

I would also make sure that head presure is well controlled, If the unit is 20 years old, you should replace the TXV, its liftime is about 10 years.
Hith HG defrost contolled by KVL, it takes time for all the liquid to boil after defrost cycle and you just might come in that time.
Also if KVL is old, replace it.
KVL is Dafoss = CRO by Sporlan

[monkey spanners]

What they ^ said, also have read that blended refrigerant can seperate in the accumilator, as its like taking vapour out of a refrigerant bottle/jug.
Another point on the milky oil is that different brand oils don't always mix well.

Measuring your suction superheat will point to if its due to liquid refrigerant in the oil.

[install monkey]

insulate it:)

[Royal241]

What they ^ said, also have read that blended refrigerant can seperate in the accumilator, as its like taking vapour out of a refrigerant bottle/jug.
Another point on the milky oil is that different brand oils don't always mix well.

Measuring your suction superheat will point to if its due to liquid refrigerant in the oil.

I never understood the difference between horizontal vs vertical accumulator, never thought about it, was a thing based on space....wow, that makes sense!
Chemi- yes it was 1/2nd after defrost (makes me fell better)
Didn't return to site, will take a few days but will post end results, very nice well thought out suggestion, thanks guys.

[Magoo]

I would suspect theTXV, the enthalpy of SST should not freeze at compressor suction if TXV superheat is controlling correctly, accumulator to protect from saturation after defrost.

[Royal241]

every 10 years is the rule on a txv, so, I have 1 on order and will also do a better evaluation on the freezer before and after replacement. been delayed by some other work, but will get there soon. tx