Have a gen 3 Nest, working fine for years, Decided to connect a whole
house humidifier to the Start terminal, after doing so the backing plate
on nest starts to heat up, The Wire from the Nest goes to the humidifier
then to com on the HVAC
Found the issue, It was because the old 2001 Aprilaire 700 humidifier
that the Nest was connected to was an older fan model, the fan relay
circuit board 110v on the humidifier was back feeding into the nest
causing the back plate to heat up, Replace ...
