wrote in message news:KOwxr.7744$% snipped-for-privacy@viwinnwfe01.internal.bigpond.com...
Some of guys answers of pulling vacuum on systems got me interest and what got me most that you believe what manufacture tell you, well gents those that believe are fools, first of all you need to work for manufacture and go on seminars to manufacture and see for your self what is done and how is done. Vacuum should be pull down to 50 microns on any new refrigeration system. If refrigerant was already in the system refrigerants that use POE oil it may take hours are days to get down to 50 microns so it is acceptable if you can get down to 100-300 microns, However it is also necessary to have system pressurize because there are times that system may leak in one direction but not in the other. Thec. At site most determined how he/she will proceed and what he/she will need to do the job right. If system lost gas on the high side or low side it makes large difference and if system has pressure safety switches that will shut down system if refrigerant is lost. There is another phenomena how cold this system is use for we must remember that all material shrinks with low temperature and expand with high. These phenomena may cause unit to leak at one temperature but not the other, I have seen and experience these problems on my own, as some of us may say it will drive you to drink even so I don't drink. Pressure testing is necessary but one most take precaution, up to 300 PSI any system can be check, sealed units you can go up to 400 PSI. Semi hermetic unit I would not advise any one to go above 300 even so I have. By the way I never heard of 45% silver on less is on special order so that Manufacture will need to sit bare assed on fire before I would believe them!!