[Richard]

Just sort of dogpiling on this thread. Neither my front or back work. The front is an open circuit somewhere. The back is a shorted circuit that gets one tile hot enough to burn you. I killed the circuits on both and the breaker box.
The reason for the post is to comment on why I think all the floor heat units in these era coaches fail. When doing some remodeling I had the occasion to take up a few pieces of tile. The construction is about 1/2 inch of grout, a layer of fiberglass mesh, and another 1/2 or so of grout. Nice 1 inch slab of reinforced concrete to keep the marble from cracking.

Having installed heated floors under tile in a house with the Schluter system, it makes sense that with the heat cable imbedded in solid grout that there is no way the heat tape is allowed to flex very much during the heat cycle, plus if the floor flexes the flex is transmitted to the heat cable. The point is, that if you remodel and want heated floors, make sure that you use some type of substrate system designed to allow a bit of flex.