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So in my basement I want to add lights to 4 rooms. A total of 18 LED lights on 5 switches from one power feed. This would be a 15 A feed all 14-2 wire. Switches 2 & 3 would be a 3 way switch for Room #2 - this would have an additional 14-3 wire between.

First question: for Room #2 from Box #2 to Box #3 - Am I correct in saying it needs 3 cables?

  • 1st cable - Power/neutral in 14-2
  • 2nd cable - Power/neutral out to box #3 for switch #4 and then to switch #5
  • 3rd cable - Traveler wires (2 travelers/1 neutral) 14-3 between boxes for 3 way between switches #2 & #3

Second question: At each box would you just pigtail the power in / power out and power to the switch?

Third question: Is 14 the correct gauge wire since the whole load is less than 3 amps?

Basement Lights 2.0

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    Why are switches 2 and 3 connected as a 3-way switch? – ThreePhaseEel Dec 2 '18 at 15:01
  • @ThreePhaseEel Maybe it is actually 2 switches in box 3 - one for room # 3 and one a 3-way for room # 2? – manassehkatz Dec 2 '18 at 15:11
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    I want to be able to turn Room #2 on and off from switch 2 and switch 3. Yes 2 switches in box #3 – Derek Dec 2 '18 at 15:31
  • Your first question is very confusing. Please revise it for clarity. Protip: spell out numbers when they're referring to quantities of numerically-referenced items. The third question isn't really a question so much as a statement. Are you asking for confirmation? – isherwood Dec 2 '18 at 15:40
  • Yeah, when you see yourself writing "3 /3 cables” instead write ”three /3 cables" to break up the numbers and be easier to read. – Harper Dec 2 '18 at 19:03
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For the /3 circuit, it is improper wiring to allow currents to be unequal in any cable or conduit. That means the 3-way must be handled carefully.

As drawn, you will have two neutrals between rooms 2 and 3. They must not be paralleled, so don't tie them together in room 3! What's more, because of the equal-currents rule, the power traveling to the lamp via either traveler, must return in the neutral in that same cable.

With two groups of neutrals in the same box which must be kept separate, the next guy is likely to make a blunder. His viewpoint will be "the last guy was an idiot, why didn't he join these neutrals, because you join all neutrals right?" I see 3 ways (heh) to head off that problem.

I am a huge fan of marking wires with tape. (And cables with tape too when needed for confusion). I prefer black for always-hot, red for switched-hot, and any otherwise-unused color (typically yellow, get it, brass screws, yellow) for both travelers. (neutral must be the white wire). Because of the way travelers work, there is no need to distinguish them from each other.

So way #1 is proceed as you are and mark the wires. Mark the 3-way neutral (in the /3 and onward to the lamp) with gray tape. That doesn't come in the $4 five-packs of colored electrical tape (red blue yellow green white), so you can use green.*

Way #2 is to flip the 3-way, so the cable to "room 2" lamps comes from box 2 rather than box 3/4. In that case the wire functions in the /3 cable would be traveler, traveler, switched-hot. Those three wires would go straight to the 3-way and not splice at all, making the separation very clear.

Way #3 is to use /4 cable. Being all in one cable satisfies the "currents must be equal" rule no matter what.


* A technicality. Green is ground... white/gray is neutral... all others are hot. White/gray can be re-marked to a hot, but all other category changes are illegal, and thus, invalid. So put green tape on a white wire, it's still neutral. Doesn't work for any other color.

  • Harper, on Way #2, which seems the best. Would power still come into Switch #2 from Switch #1 or would I have to run power from Switch #1 to Switch #3 first, then just the traveler wire from Switch #3 to Switch #2? – Derek Dec 2 '18 at 21:03
  • Either way, I would run power to "common" (black screw) on switch 2, travelers to switch 3 and switched-hot back off the common of switch 3. You could run hot to switch 3 first if you wanted, but you must be careful not to use hot from the other cable or cross them. – Harper Dec 2 '18 at 21:06
  • So switch #2 has power coming in - hot black / white common – Derek Dec 3 '18 at 0:24
  • @Derek when I say "common" I mean the black screw on a 3-way switch, which is the proper name for that terminal. The white wire has nothing to do with common, its usual function is called "neutral". – Harper Dec 3 '18 at 0:30
  • So skipping ground wires, switch #2 has Power coming in - hot black / white common (2 wires) Load (lights) coming in - hot black / white common (2 wires) Travelers 14-3 - black / red / white common (3 wires) All white common get tied together? Power coming in - hot black -> to "common" (black screw) 3 wires left, but only 2 terminals on switch Black from Load -> ? Black traveler -> ? Red Traveler -> – Derek Dec 3 '18 at 0:31
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First of all, as I edited in the question, wire normally refers to a single conductor. Multiple wires inside a outer covering is referred to as a cable. 14/2 and 14/3 are common cables, each containing multiple insulated wires (2 or 3) plus a bare ground wire.

First question: for Room #2 from Box #2 to Box #3 - Am I correct in saying it needs 3 cables? 1st cable - Power/neutral in 14-2 2nd cable - Power/neutral out to box #3 for switch #4 and then to switch #5 3rd cable - Traveler wires (2 hots/1 neutral) 14-3 between boxes for 3 way between switches #2 & #3

That is the typical way to do it, though it uses a little more wire than the minimum. You could use a single 14/4 cable between box 2 and box 3. This would have hot (black), neutral (white), 2 travelers (other colors). The advantage is you save one wire because the neutral can be shared since this is all part of one circuit. However, if you already have (or will be getting) 14/3 for other 3-way switches then running 14/2 + 14/3 is probably cheaper than getting 14/4 just for this one installation. As noted by Harper, if you use separate /2 and /3 then you must keep the neutrals matched to the hots/travelers and not connect them together in room #3 (i.e., switches #3 and #4).

Second question: At each box would you just pigtail the power in / power out and power to the switch?

Correct. Pigtail hot (black), neutral (white), ground (bare) and connect to switches as appropriate.

Third question: Is 14 the correct gauge wire since the whole load is less than 3 amps?

Correct. Just make sure that the circuit breaker is also 15A to match.

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    +1 for edit alone! – Harper Dec 2 '18 at 21:07

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