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I am planning on hardwiring 6 combination smoke/CO detectors on various levels of the house (2nd flr, 1st flr, basement) using 12/2 wire branching off from permitted sources (standalone 20a outlets).

Per IRC 314.3 and 314.4 I understand what the detector locations need to be and that they need to be interconnected, in order that they all sound an alarm when one of them does.

Kidde sells a great combo detector which communicates with its siblings via RF, thereby fulfilling the "sound one - sound all" requirement. I am planning on using this type of detector for all 6 of mine.

I have searched high and low to find anything in the code (IRC 2015, NEC 2017, NFPA 72) that requires the smoke detectors to be HARD-WIRE INTERCONNECTED, instead of wirelessly interconnected, and found nothing.

Question: Can anyone point to a code section applicable to residential family housing where a hard wire interconnectivity requirement may exist?

The inspector mentioned he thinks detectors must not only be hard wired for power (which i will do) but also interconnectivity.

It would be a lot of extra work and intra-drywall fishing, let alone buying the 14/3 or 12/3 wire to do that, literally costing more and being more time consuming without any gain in safety, so i want to make sure i'm on solid footing if i have to defend my choice.

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  • R314.5 seems pretty clear that wireless interconnection is permitted: "Physical interconnection of smoke alarms shall not be required where listed wireless alarms are installed and all alarms sound upon activation of one alarm." Jul 22, 2021 at 21:27
  • My local IRC 2015 code version omits that wording as section 314.5 looks like this - up.codes/viewer/connecticut/irc-2015/chapter/3/… - but it also doesn't specifically state a wired requirement. Aside from some very unusual electromagnetic interference messing with the RF signal between the detectors (like running the microwave with the door open), i really don't see a downside, but i welcome any input that i may be blind to due to my potential confirmation bias.
    – sil80
    Jul 22, 2021 at 22:25

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There is not such a section, because there is no such requirement

The requirements for interconnect are designed intentionally to be technology-agnostic; as long as UL has put its stamp of approval on the system as part of the listing process, and it works in the field, you're good to go under the current model Codes.

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  • That's what I thought, I just needed some confirmation I wasn't missing anything, much appreciated, ThreePhaseEel! I have another question related to detector placement if you don't mind giving it a shot - diy.stackexchange.com/questions/229649/…
    – sil80
    Jul 23, 2021 at 2:50

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