I have a less than 1 yr old carrier 25HPA536A310. Installed last August. Stopped cooling effectively. Tech came out his notes are: and "Added 3lb 10 oz of R-410a to bring subcool to speed. 11 deg., press 250/48 w/87 deg. sat temp and 74 deg. LL temp. No indication of overheat to TXV buld. TXV is only possibility. 7 deg. split." I know nothing about this, but should this much R-410a need to be added to a new system? It cooled fine last Aug-Sept when installed. I've read other posts here where TXV replacement was more than common. Any ideas what could be wrong? Faulty installation? My warrenty is up in August so I do not want this to be a hunt and peck every month until I'm out of warranty. Any help or direction appreciated.