Quote:
Originally Posted by ganun
if I remember I put a little over a can (12 oz can) in my converted system, I don't see 50 oz going in there.
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1) If you mean you could only get 12 oz into an empty stock 911/930 system and not more, then the issue might be you did not properly evacuate the system; you did not remove all the ambient gases (air) from the system or your charging hoses before your charged the system with refrigerant. And, as well, an evacuated system that is sitting in, say, 70F ambient air, will only take about 12 oz of refrigerant (using a 'cold' can-same temperature, of refrigerant) with the compressor off (hence is why a professional charging system would charge via a liquid method with a heated cylinder).
You don't need a P&T chart to figure that out; review your evacuation and charging procedures.
2) If a stock system previously used 48 oz of R12, then it will typically use 85% nominal of R134a. So in theory, you will need 38 ounces +/- x ounces for the system. During the procedure you will need to purge the service hoses you use to put refrigerant in the system. Common service hose inner diameter is 1/4" and can range from 4 to 5 feet. The volume of refrigerant needed to purge using liquid refrigerant is about .33 oz per linear foot. Purging 10 linear feet of hose, and your gauge manifold, will take about 3 to 4 ounces in a perfect world; if you do it perfectly. If you want to perfectly charge 38 ounces of refrigerant you would then need 41 to 42 ounces of refrigerant in total; if you do it perfectly. That would mean either (4) 12 oz cans or (3) 16 oz cans. But..... for most DIY using small cans "things" happen, such as a bad tapping of a can leads to refrigerant losses. If you are charging with a 30 pounder and a scale you can monitor the process and avoid losses.