I understand that normally, the NEC is not happy with mixing voltages in raceways, but I have an odd situation. I'm installing an electric radiant heated floor in my bathroom, and the thermostat I have chosen comes with a remote temperature probe. I roughed in a deep j-box with sealtite run down through the sillplate, even with the floor so I can fish their special lead wires in when I'm ready to lay the floor. I then rocked the wall. Then, it occurred to me to look through the manuals, and they state that the remote floor temp sensor needs to be run separately, which makes sense from an NEC standpoint. This is when I found out that there was a remote temperature sensor! That being said, I'd really hate to deal with fishing this little cable up to the j-box, given how the wall is framed. Equally, I'd hate to fish a second conduit to this 1-gang j-box just for a 20-guage wire.
The odd part is that the sensor still needs to enter the j-box to get to the back of the thermostat, so it's not like the code is truly followed. You would think that the most-likely place for low and high voltage to accidentally come in contact would be in the j-box. So, my thought would be to use rubber refrigerator ice line (clear) and fish the sensor wires through that, then fish that through the high-voltage conduit. This way, I'm double-insulating the sensor wiring. Another possibility is to splice the sensor wiring to listed 20-guage thhn wires with the same insulation rating as their lead wires and fishing that through.
The legal way I have seen to mix class 2 and line voltage in a conduit is if both are cables. You need to split them out before you cut into the cable jacket. (something like a "T" condulet at each end)
#204869 - 01/17/1203:15 PMRe: Mixing high/low voltage in the same conduit
Now that I look at it closer, I DO see that unique type faceplate. Good eye! Bad for me, but good eye! I think I'll still run a rubber water line tube, but outside of the conduit, attaching it right below the j-box, so that I can fish in the sensor at a later point. The main problem is there is a fire block between the j-box and the floor, so it looks like I'll be doing some wall surgery. Ugh. Better now than later, I guess.
#204875 - 01/18/1212:48 AMRe: Mixing high/low voltage in the same conduit
Well, I blind-fished the stupid wires outside of the conduit, through the fireblock hole that that conduit went through. Since the fireblock hole was about a foot to the right of the jbox, I needed to hook it with a short fishtape from the gap under the jbox. It was the best blind double-fish job I've ever done. No wall surgery, and it only took me 15 minutes. I re-learned a valuable lesson to read the manuals of oddball electronics BEFORE you rock the walls. It would've saved me a lot of time.
#204973 - 01/26/1212:35 AMRe: Mixing high/low voltage in the same conduit