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2017 NEC 210.70.A.2 gives the following exception:

Exception to (A)(2)(1), (A)(2)(2), and (A)(2)(3): In hallways, in stairways, and at outdoor entrances, remote, central, or automatic control of lighting shall be permitted.

I have a stairway in my attached garage that goes up to a loft area.

Does the exception above mean I can satisfy the lighting circuit requirements if I install one motion sensing switch at the bottom of the stairs and another at the top, to control the lights in the stairway, without any wall toggle switches?

Also, I understand how to make the lights come on if one or both of the motion switches activate—just wire the switches in parallel. But am I allowed to do that? Do I need to add any special labeling anywhere to indicate the parallel operation?

Very similar to this question but I'm in the United States.

2 Answers 2

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Where lighting is required, a motion activated switch for such lighting must also have a manual on/off switch. This requirement is usually implemented as an on/off/auto switch.

So two motion activated switches in parallel are fine, as long as both have the manual override (which all generally do). No labeling required, but the switch must be placed at the usual position (4ft from floor, at top and bottom of stairs). I'd assume that's where the current box for the switch already is.

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  • Can you cite this requirement, or point me in the direction of finding it? Dec 11, 2021 at 14:49
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    @MattThomas sorry I searched but now can't find the reference, although I do remember reading it. I'll tag you if I come across it again.
    – P2000
    Dec 12, 2021 at 1:34
  • The reason I ask is because the exception in my OP is just that... an exception. If they intended to say "you can control the lights with stuff in addition to switches" then I'd expect it to instead be an informational note Dec 13, 2021 at 13:43
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Some wall mounted occupancy sensors have a contact operation to manually override the motion sensor, so I would think would satisfy the 2017 version of the 210.70 without even applying the exception. Incidentally the 2020 version changes the wording to "wall mounted control device". If the local authority hasn't adopted the current edition and you think using a newer version of the NEC might give a local inspector heartburn you could call them and ask.

No you can't operate switches in parallel, at very least 1/0 awg is the minimum size conductor allowed in parallel, but many occ sensors come in 3-way versions that use one of the existing travelers as a signal wire.

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  • I don't think the 300.3(B)/310.10(H) concern you mention applies to paralleling switches, only when you're trying to increase ampacity by paralleling wires Dec 11, 2021 at 20:40
  • I suppose I would have to invoke the exception in 310.10.H.1: operate the switches in parallel to trigger a relay that powers the lights from the same breaker. If that wouldn't cause future owners and electricians to scratch their head then I don't know what will. I think I'll ask my AHJ, and will keep multi-location sensors in my pocket as an option. Dec 13, 2021 at 13:35
  • I asked my AHJ and he said there was no problem with operating the switches in parallel for essentially the reasons @ThreePhaseEel said. But he also said that he personally hasn't had luck doing it because of something inherent to the occupancy switches, perhaps related to the fact that when one of them switches on, the other gets line voltage on its switched side while off. Whatever the reason he said he has experienced them failing to work outright or failing early when operated in parallel. For that reason (and not for the parallel conductors reason) he recommended multi location sensors. Dec 13, 2021 at 14:18
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    @MattThomas it's possible that the sensor in question also had an ambient light detector which effectively disables the second detector if the first one is triggered. Another issue could be wireless sensing, where two detectors co- interfere with one switch that they are wirelessly associated with. Other than that, I cannot imagine two plain-vanilla switches (which are effectively relays on the line side) causing mutual trouble. You could contact a manufacturer (Lutron, Leviton etc.)
    – P2000
    Dec 13, 2021 at 15:39
  • @MattThomas -- did your AHJ mention any specific makes/models of wallbox sensors that didn't like that sort of operation? Dec 13, 2021 at 23:38

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