I own an apartment building built in the 70's that is heated electrically (and it works surprisingly very well and is cost effective). Each room is zoned. The second (top) floor has radiant heating in the ceiling. It consists of "90 degree radiant heat cable" (a thin gauge stranded wire that is coated and less than 1/8" thick) that serpentines across the ceiling about every 2" apart. This heat cable is sandwiched in between two layers of 3/8" drywall that is adhered together (although adhesive comes apart pretty easily). I had to replace a section of ceiling and was successful in getting it apart and repaired pretty easily and was about to reinstall the cable when I discovered that the radiant heat cable had broken in one spot.
The cable (which is tan in color) says "Yellow Yellow Yellow... Radiant Heating Cable E27819 (UL)". The thermostat is a mears M7D, 18Amps. I do not know if the entire system is Mears or just the thermostats.

Does anyone know anything about this system? The brand and how to get in touch with the manufacturer. Where to get repair and new supplies. What the adhesive is?
Most important, how to repair the cable so as to not create a problem such as a hot (or cold) spot at the repair that would be dangerous or create a significant problem. (The repair would need to be pretty thin but could be thicker than 1/8")
What is the life expectancy of this cable?
Any and all information or sources for info or supplies or leads in this direction will be appreciated.
Thanks,
Mark

I do not believe splices are acceptable in the enclosed radiant heat line itself.
You will probably have to replace the cable unless you can find a approved splice kit.
I recommend that you install electric baseboard heat in that room. Make life simple for yourself.

As a contractor for way to many years this was the solution to this problem many times due to the strict UL standards of no concealed splices and that means no splices in the sandwich drywall.