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enter image description hereI have a store in a commercial building. I have two switches that were wired up with 14/2 Mc wire. A leg from the breaker and one from the light. Inspector came and said the reverse switch legs need a neutral. I’m confused as to why, when they were wired with MC that has a neutral in it already. I have a fan that’s to be added. But I don’t think that would make a difference. I’m confused on the needling a neutral when it’s already in the box. Please help

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  • Does the power from the panel/breaker go to the light first then to the switch? That is a switch loop and does not have neutral. It uses the white wire as a switch hot or hot wire. Neutral must be white(or grey), but white does not need to be neutral.
    – crip659
    Dec 19, 2022 at 21:11
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    Yeah, read up more on "switch loops" so you understand them better, never heard of a "reverse switch loop". A white wire is not necessarily neutral. The bare or green wire is definitely not neutral.
    – Harper - Reinstate Monica
    Dec 19, 2022 at 21:27
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    If a circuit is not changed then a switch loop should be okay, if it was in code when made. Inspector's word is the "law" though and is usually cheaper to go with what they say. Make inspector happy and you enjoy happy days.
    – crip659
    Dec 19, 2022 at 21:59
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    I think the inspector is calling it a "reverse" because it is panel -> fixture -> switch -> fixture instead of panel -> switch -> fixture. But the term "switch loop" (as I have learned here at DIY SE) incorporates the "reverse-ness" in its very essence, so that "reverse switch loop" is repetitively redundant.
    – manassehkatz-Moving 2 Codidact
    Dec 19, 2022 at 22:29

1 Answer 1

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Repeat after me:

WHITE IS NOT NEUTRAL!

Standard /2 cables are black and white. Standard /3 cables are black, red and white.

NEC colors are:

  • Black, red, blue, yellow, orange, etc. are hot
  • White and gray are neutral
  • Green, bare, green/yellow are ground

The problem is that if you only need "hot" wires (that includes hot (generically), line (hot "in"), load or switched hot (hot "out"), travelers in 3-way switches) and your cable has exactly the right number of wires but one of those is white, you can use the white as a hot wire, though it should be marked with black or red or some other "hot" color tape to indicate it is hot. Classic examples are:

  • 240V circuit that does not need a neutral - /2 cable, black and white both hot
  • Cable between 3-way (and 4-way) switches - depending on configuration, this can be line + 2 traveler (all hot), neutral + 2 traveler (in which case white must be used for neutral), switched hot + 2 traveler. In any of these cases that don't have a neutral, white gets used as a hot wire.
  • Switch loop - hot and switched hot.

So within certain constraints you can use a white wire as a hot wire. It is not using a neutral wire as a hot wire - because that doesn't actually make sense - a wire is either neutral or hot, it can't be both at the same time (Schrodinger's wire?).

However, there is a big catch. Switch boxes are now required to have neutral in each switch box. This is in order to make it easier to add smart switches/motion sensors/timers/etc. which require power of their own. These devices are becoming more common as the electronics get cheaper, plus one of the old methods of getting power (leak a bit of current through a light even when "off") does not work well with LED lighting. So code says "new stuff, make sure there is a neutral in the box, even if you don't need it right now."

There are certain exceptions, primarily dealing with conduit (because then you can add a neutral later if you need it). And existing wiring is grandfathered - e.g., if you add a new circuit you need to include neutral to every switch box but you don't have to change the wiring to your existing switch boxes.

You are adding (as far as the inspector is concerned) some new stuff. So you need to comply with current code for that circuit and switch boxes - i.e., if it needs inspection now, it needs to be to current code. (Not to be confused with a "home inspector" - they may point out old/new/good/bad but they can't make you change anything. The city/county/state/etc. electrical inspector is looking at new or changed or updated stuff and can tell you what is required for that stuff.) The inspector is saying "You need a neutral in each switch box that is added or updated". Your response of "See that white neutral wire?" is useless because it is not neutral - it is white but used as a hot wire. If you point out the switch in the next room that was wired exactly the same way 10 years ago, the answer will be (or should be) "Yes, that's fine because code allowed that at the time, but your new switch needs to comply with today's code."

The end result though is that for a new switch, you need to have either a /3 cable:

  • black - incoming hot
  • red - switched hot
  • white - neutral - even if you don't need it right now

or:

2 x /2 cables:

  • Cable 1 - black/white hot/neutral from the panel
  • Cable 2 - black/white switched hot/neutral to the light

If you have two switches for two light fixtures on the same circuit then you can either do two /3 cables or:

3 x /2 cables:

  • Cable 1 - black/white hot/neutral from the panel
  • Cable 2 - black/white switched hot/neutral to light 1
  • Cable 3 - black/white switched hot/neutral to light 2
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  • Ok thanks for the explanation, though still a bit confused. One leg is from the panel to the switch and the other is from the light to switch. Should a /3 wire be ran? It’s a new room so it needs the up to date code. I have another switch that was moved, so it now needs to be updated I was told. Sucks. No 2 way switches are needed. It’s just a bathroom.
    – Media Xpresso
    Dec 21, 2022 at 0:09
  • Is each of these black/white/green MC cables for a different switch? Or are they all parts related to one switch? If they are for two different switches (and two different lights) then the inspector is 100% correct (for a new install) and you need to either have one cable coming in with hot/neutral and two cables going out with switched hot/neutral. If they are all for one switch then it should not be a problem making this all work correctly without extra wires. Need clarification of what we're actually seeing in the picture.
    – manassehkatz-Moving 2 Codidact
    Dec 21, 2022 at 1:05
  • All for one switch. No 2 way. Just a commercial bathroom light. That box is in the bathroom. One leg from the panel. One leg from the light.
    – Media Xpresso
    Dec 21, 2022 at 3:02
  • Now I'm totally confused. If you have MC with black (hot)/white (neutral) from the panel and have MC with black (switched hot)/white (neutral) going to the switch, it doesn't look like anything is missing. I thought originally that you had terminology confused and had one cable with one wire from the panel (but routed via the fixture box) and one wire going to the switch - which is an old-style no-neutral switch loop.
    – manassehkatz-Moving 2 Codidact
    Dec 21, 2022 at 4:28
  • Yeah. Same as I am. The inspector will be back tomorrow and I will have him explain what he means. Everyone I ask is confused, and is not sure why a 4th wire needs to be in the box for one light. Thanks a lot for your help.
    – Media Xpresso
    Dec 21, 2022 at 5:40

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