I recently installed a warmup 120 volt matting system in a restroom along with an uncoupling membrane and porcelain tile, for some reason i can't figure out the thermostat wont power up.

This is my setup: 20amp breaker 12/3 running to thermostat then the factory wire running from thermostat to floor warming system. Seems pretty simple but i cant figure it out, i used the multimeter to test the line and have 120 in the thermostat box, opened the breaker panel back up and checked everything inside (wires connected good) still getting good reading for resistance on the warming mat. Also have tried two diffrent thermostats.

Is there something i'm not thinking of?
Any help would be appreciated.

 

What t stat brand and model are you using?

Should be wired like this I believe.

 

Basically a black and red from the t stat goes to line power, and the other black and red go to the load.

 

Does your mat require 120 or 240 volt supply?

 

The system I installed uses 120 so I have the black load hooked
up to the power coming in and the red load to the neutral, then
the line wires hooked to the warming mat

 

Neutral is never switched, red is never hooked to a neutral so unless the thermostat has a white neutral is never hooked to the thermostat.

Neutrals (whites) are connected only to each other. If this is a two pole thermostat only one pole is used. The other is capped off or get a single pole thermostat to make things simple.