I use a maverick ET-710S remote thermometer, first I put the probe in the water tank of my Maxim pellet boiler. after 1 day the moisture got into the probe and it started reading 285* in my 175* water. I brought it inside and put it on a copper pipe in my basement that is part of the boiler loop. It dried out and now reads about 5* lower than the actual water temp. I have it on a part of my loop after the house HX so I can see how low my water temp gets during a cycle.
When the remote probe was outside I kept loosing the signal and having to go out and reset them both, now with the remote in the basement I don't ever loose signal.