We have a bathroom with the tile floor heating comming up. We done them before but was wondering somthing. If the tile guys leave way to much heating wire in your box can it be cut to fit? Or does that case problems with the resistancee? Can it be put in the box or will the box get too hot. Do we just need to make sure the tilers use up the extra wire in the floor and not the box?

If I remember on 1 mat there are 2 leads with a metal sheald. The shield would be grounded?