Post by don on Sept 4, 2016 15:34:18 GMT
I searched this forum and found that the issue of refrigeration oil viscosity had been discussed but not in a dedicated post so I decided to start this one for posterity's sake. Attached below is a cropped scan from a 1934 GE service manual for the first flattop refrigerator that used a belt driven rotary compressor that used SO2. Probably because the shaft seal was a serviceable part they tell us that only special GE oil should be used in GE machines. Catalog No. C16A24
Also attached is a scanned page from a 1940 Refrigeration supplies catalog. The Texaco capella oils were at that time made in six weights and the one recommended for GE is #9270 AA with a SUS viscosity of 75-85 viscosity at 100F and a pour point of -45F.
The Official Refrigeration Service Manual from 1935 provided on this forum by "coldspaces" also tells us that SO2 systems use 75 viscosity oil on page 49. If using R12 the manual advises to use 150 viscosity and to add extra oil to account for the oil that circulates in the system with the refrigerant. Beginning on page 48 and continued on page 49 of the manual it states that the heavier oil is necessary because R12 mixes with the oil and thins it out in contrast to the SO2 which has a limited oil miscibility.
It appears that the 150 (3gs) viscosity oils manufactured today have a pour point of -40 F (C) which is almost identical to the pour point of the 75 viscosity Texaco AA #9270 oil from 1940. This appears to help reinforce the use of 150 (3GS) oil as the one and only choice for a SO2 system with todays selection of mineral oils?
Maybe if someone could compare the pour point of a cup of the original oil from a methyl formate CA rotary compressor and a cup of 150 (3GS) oil in a -40 degree F temperature chamber we could make a guestimate on whether 150 (3GS) would be the closest replacement for the CA compressor? If the original methyl formate oil did not pour at -40 that might indicate that 300 (4GS) would be a closer match? It would take a cascade refrigeration system to reach that temperature for that comparison.
Maybe someone can have the viscosity measured???
