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View Full Version : r134aas anr12 replacement



Les Stuart
03-04-2003, 11:06 AM
Do we always need to change oil when doing a conversion.I would like to know if anyone has tried it and had success.

Latte
03-04-2003, 07:21 PM
Basically YES !!!!!

Most R12 Systems used to run on mineral oil which is no good for some of the modern gases. It can be done, i know of systems that have had just the gas changed and run ok. The main question has always got to be "what is the oil condition".
I have always found that if i am unsure about the oil CHANGE IT.
whats the point of spending time & money repairing a system and then the compressor seizing in a few weeks just because you cannot be bothered to change the oil.
I always have (If possible to do so) and will always will change oil & Driers on a system that i am changing the gas on.
I appreciate if you have only repaired a gas leak on a small domestic unit that you can't change the oil but if you can experience tells me do so if possible

adacus1
31-07-2003, 04:27 AM
Most R12 system compressors were charged with a mineral base oil although some synthetics were being used prior to phase out. Mixing R134a and Mineral base oils will result in a long system clean up job as the result is a creamy / white 'gel' difficult to describe but never forgotten if you have cleaned a system with it in.

R134a compressors will typically be charged with either - PAG Polyalkylene Glycol or POE Polyol Ester oil. Both of whch are synthetic oils.

Successful retrofit from R12 to R134a requires the oil to be changed to one or the other synthetic oils and the mineral oil content dropped to less than 1-2%. This means more than just changing the oil in the compressor as there is always oil around the system. Doing the change in three steps basically diluting the oil at each change is successful although time consuming. Change the oil and then restart the system and run with the maximum capacity to induce the highest flow rates around the whole system, flushing oil out in the system back to the compressor. After 1-2 hours change the compressor oil a second time and repeat. At the end of this second change recover the R12, change the compressor oil the final time, change filter drier and recharge with R134a. The charge required will not be the same as the old R12 system but for the life of me I cannot remember whether it goes up or down as I havent done one in about 4 years - I will check it out tomorrow. The system capacity will also decrease 8 -10% depending on the system configuration