We are installing a low voltage device to controll a gas fire place. Can I use the low voltage cut in boxes (the one without a back) to mount my device in. Where is it in the code.
I don't think there is something that directly says it is OK.
300.15 requires a box at switch points. However, 725.3 states that only the sections of article 300 that are referenced in 725 apply to Class 1, 2, or 3 circuits. I don't see 300.15 referenced, so, no box required.
You would have to check the fireplace, but I would think it is classified as a class 2 circuit.