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It is common practice to add a small amount of propane to the low stage in a cascade system. I know that someone, ASHRAE maybe, had defined a minimum ratio of propane to refrigerant for flammability reasons, does anyone know what that is or where I can find it in writing?
I add 1% > 2% to 404 507 systems. it does wonders with oil return.
Try google, if its on the web, you can find the info.
HI,
What is role of R-290 in oil returning?
R-290 is a very good oil carrier.
we use r290 in in -80C ultra low freezers... the r290 is mainly for oil return purposes 10grams is all we use in each cabinet
B”HQuote:
Originally Posted by padraic
Padraic,
10 grams of R-290, what it is a percentage of the totals charge.
fine, i am going to make ultra deep freeezer in next month, i will do it, thanx
yeah, worked on one -80 and we had to charge the low side with pentane which is a flammable liquid, but again the only reason was for oil return and the plate give us a weight in oz to charge how much of it in the low side