oil mixture

[chillyblue]

Hi

I'm not certain but i belive that a -20deg walk-in freezer, which has had a new evaporator and condensing unit fitted may still have mineral oil in the system :rolleyes:
The system is now operating on R404A with polyester oil but by the age of the room i would think it would have been mineral oil originally.
The system is operating with a low evap temp of -40deg and the TEV is very eractic (either low superheat or high superheat, The TEV is of the correct size).
I've checked and changed the liquid line drier.

I am assuming that if mineral oil has been left in the system and has mixed with the new poly oil it may be blocking or restricting the flow through the TEV, if this is the case whats the process of checking to see if mineral oil is in the system and the process of clearing it???????

Thanks CB

[Thermatech]

you need a refractrometer.

1/ measure new mineral oil with the refractrometer & note the reading.
2/ measure new synthetic oil & note the reading.
3/ remove an oil sample from your system & using the refractrometer note the reading.
4/ using the data you have collected to calculate the % mixture.