operating

My newly installed TrailTech Vapor unit tells me lots of good stuff. I installed the temp sensor in the radiator return hose, just above where it comes off the engine: What I'm finding is that at idle (no load) it will hang around 180 or so - seemingly indefinately but I guess I didn't...

can anyone tell me what operating temp a 2005 fe450e would normally operate at at a steady pace,,,,,? and what temperature is to high that i should shut down? just got some temp strips for it