Ecobee3 Installation on a Mud-Ring / Electrical Box

I purchased an Ecobee3 during a black Friday sale and was all excited when it arrived. That excitement was short lived once I discovered the supplied mounts are made exclusively for drywall.  My existing thermostat was mounted on a mud-plate. My current thermostat as well as my previous thermostats came with brackets which fit the plate. 

I contacted customer service but was told they did not have any other mounting solutions. This was surprising as even the Nest comes with a mounting option for electrical boxes.

Googling around for "Ecobee3 electrical box mounting" and similar terms also did not turn up anything aside from a few posts stating it did not support mounting on an electrical box.

Below is my somewhat lazy solution because I did not want to rip out the plate nor patch over it. There are probably definitely better ways, but this worked and I had all the parts on hand. YMMV.

Also, I don't know if this voids the warantee or not.

Parts required:

• Two of the small screws which came with the Ecobee3 kit
• 2 nuts that fit those screws
• A gang plate cover (metal, plastic, or wood) matching the center to center hole-distance of the mud-plate or electrical box (3 5/16" in my case)
• Drill + drill bits
• Razor or punch tool (optional)

Drilled gang plate cover

Using the Ecobee3 mounting plate as a guide, use a pencil and mark the top, bottom, and center holes. Then take a razor or punch tool and make indentations where you will be drilling.  Use a punch tool if your cover is made of wood or metal; use something sharp like a razor if it is plastic.

It broke :(

The plastic covers shatter easily, so drill carefully.

Test fit

Using a small drill bit, drill holes just large enough for the screws to pass through.  

Use a larger drill bit to drill the center hole. Again, be careful if using a plastic cover since they are fragile.  If you are worried about shattering the cover with a larger bit, you can use a smaller bit and bore the center hole out (or use a zip-saw).

Test-mount the Ecobee3 on the cover. Now remove it. Don't install it like this or you will end up with the picture below (notice a problem?):

Dammit! Forgot some holes.

The Ecobee3's bracket is blocking the screw-holes of the gang plate cover. There's no way to fasten the gang plate cover to the mud-ring.

Extra holes for mounting

You'll need to drill two more holes, but this time in the outer Ecobee3 bracket (remove the outer bracket before drilling).

The bracket happens to have tiny little raised bumps exactly where I needed to drill. The holes need to be large enough to fit your screwdriver through. It is through these holes you mount the gang plate cover to the mud ring.

Mount the Ecobee3 itself.

Shiny!