A couple of weeks ago I went on a call for a unit vent overheating a room. heating valve 100% open and fan running. I connected to zn520 with rover and I found that setpoint was correct from thubwheel (cooling) but discharge air temp setpoint was for heating (150 or so can"t remember it has been awhile). So I downloaded controller and it seemed to operate fine until I disconnected then the same happened again. So I ordered a new zn520 and downloaded and everything was ok for maybe two weeks and I get a call on this again, I can only assume it is doing the same thing I was told it was overheating and the fan wont shut off, same as before. The bus of trane unit vents goes back to a metasis controller but I cant believe this is causing the problem because this is one of 100 uv's on site.