Hello all! Need some help. I have been working on a R409A system, it is 130 psi head, and around 27 pound suction. First call out I got was unit was tripping out on lp, drier was 100 years old (as always), moisture in system, tx had iced up so I replaced tx and orifice (probably didnt really need to) and did some filter changes every couple of weeks (ran fine). But customer had complained that evap always ices up (for last four years) . I know if unit is to small it will ice up, but checked unit, not to bad could be a little bigger but power is and issue, but distributor on this system will ice up about one minute after running, and evap coil will ice straight away as well. Now i have new drier, only other thing between drier and valve is sight glass, I have new tx valve, correct orifice (I have checked). and recently bypassed heat exchanger because I thought it may have had a small leak and was not getting full liquid line. But no joy! Distributor is not blocked. So would anyone know why this system would ice up so quickly? It is really starting to do my head in.