It is my understanding that low-voltage wires can share a double-gang box with 120V wires, as long as they are isolated from each other by a permanent divider. I was looking at getting this relay to operate an inline duct booster fan using the 24V thermostat signal wire. However both the low-voltage and the 120V wires would come into the box bundled together through the same knockout. Is there an exception for relays, or something that I am missing? Or can I just punch a hole in a divider and snake the low-voltage wire through and just keep the splices separate? This is in the United States in a state on 2017 NEC if it makes a difference

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    You may note the lack of a UL device marking or a RU (the R would be backwards) registered component mark on that device...
    – Ecnerwal
    Commented May 31, 2023 at 18:25
  • The picture doesn't show the UL logo but the manufacturer's datasheet says that it is UL listed for both US and Canada
    – User41943
    Commented May 31, 2023 at 19:16
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    @ecnerwal RiB is UL listed. Amazon is not a reliable supplier though, OP, if you were wondering why the mistrust. Commented May 31, 2023 at 19:27
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    Note the ones from this manufacturer that provide the desired separation and the ones that do not are all UL listed for their respective applications. It's up to you to use them correctly.
    – jay613
    Commented May 31, 2023 at 20:26
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    I suggest you contact your inspector at the building department. I had a similar problem many years ago and I did not have to put in a barrier or anything, the only requirement they had was the insulation on the low voltage side had to equal or exceed the rating on the line side. I used 1000 volt rated wire and it passed without any problems. Sometimes they are on your side. My panels ranged from 1 relay to 24 relays.
    – Gil
    Commented May 31, 2023 at 21:40

1 Answer 1


You're on the right track. The same manufacturer (and others) make similar relays where the low and high voltage wires come out opposite sides of the device, with either the high voltage or low voltage ones coming through the knockout, so you just buy the appropriate one depending on whether you want the relay inside or outside the junction box.

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