I JUST finished doing a reno on my bathroom where we put in-floor electric heat. I can look up more specific details for you later, I'm at work and just going off of what is in my gmail history (which actually covers quite a bit!)
We used a Honeywell Aube TH115-AF-240S. This one is not a GFCI, and we probably should have gone with one. You can install a GFCI at your fuse box. We replaced a prior existing baseboard electric heat element that was running on 220, and tied into that circuit.
http://www.warmingsystems.com/easy-installation/Since my bathroom was an odd shape, we went with the 'coil' of wire instead of the mats. It made it easy to fit into odd nooks and crannies. They do have a 'square foot' coverage listed for each one. In PA, you don't need to be a licensed electrician, so our contractor did the install (I helped/watched and learned).
To prep the floor, we removed everything down to the subfloor, and installed '
backerboard' over the plywood. This reduces the flex in the floor, and also keeps most of the moisture from the cement/thinset from absorbing into the plywood subfloor.
To install the kit, we attached provided strips of metal to the floor, then snaked the coil back and forth, folding over the tabs on the strips to hold it down. In the above link at warmingsystems, it looks like they use some sort of HVAC tap to hold down the coil. Then we placed the in-floor sensors with enough length to reach back to the thermostat. They recommend putting a second one in at this point, and running it up and taping it in your box incase the first thermostat fails for some reason - then you don't need to break up your floor, you can just hook up the second sensor.
After it is all down and in place, we pour a self leveling concrete over the element/coil. If you are putting down a laminate floor it is really important for this step to be as flat/level as possible. Since we were just tiling over it, we just let it cure and then put thinset directly ontop of it. They recommend using a plastic float (or at least a non metal one) so you don't catch/nick the element.
Thoughout the entire process, they have you check the resistance in both the element and the floor sensor. If it is outside the recommend range, then the unit somehow became damaged. It is easier to find it one or two steps in then to find out after you've laid all your flooring ontop of it!
My wife loves the warm tile on her feet in the chilly mornings. The thermostat is programmable so when we'd wake up it is ready, and when we go to work it shuts off. The thermal mass of the tile holds heat well, so you can time it to shut off about an hour before you'll leave, and you'll still have plenty of warmth.
If you have any more questions let me know!
