Sounds like a lot of RTAA experience out there (good units) so I may as well jump into the mix. I beleive you just weighed in a new Ref charge? What about the oil charge? There is a method (in the IOM as I recall) of checking the oil level. It may be worth a shot. As mentioned, do not try to compare the RTAA and RTAC service wise as they are different designs and and do many things differently. Other things to look at are long periods of low load operation, low temperature operation, use of glycol ( as mentioned). Are you having load/unload problems or just low oil problems?