Electrical – Ceiling box has 2 black and white wires but fan/ light only has 1 of each

ceiling-fanelectricallight

Installing a new fan/light with 1 red wire 1 white wire and 2 green wires
The box in my ceiling has 2 black wires, 2 white wires, and one bare wire.
(The 2 black wires were capped together, and the 2 white wires were capped together)

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Manual says to connect the red fan wire to the black ceiling wire, the white fan wire to the white ceiling wire, and the green fan wires to the bare ceiling wire.

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I have connected the green wires, but I do not know how to connect the other wires since there seems to be an extra set?

Best Answer

Your fan is designed to be internally self-switched using the wireless remote. As such, it's looking for 3 wires:

  • Equipment safety grounding/earthing, which is always green or bare (even in Thailand)
  • Hot (of some kind), a current supply, which can be many colors
  • Neutral, which is a current return, which must be white or gray. (white wires are often not neutral).

Grounds are easy because all grounds get connected together in every case, unless you're doing extreme wizard-work in a test lab, audio studio or factory.

When you see two cables entering, and both blacks are already tied together, and both whites are tied together, that circuit is carrying current onward to some other point-of-use. "It's not yours to disassemble" is probably the best way of thinking about it. We have another question today where someone dismantled one of those, and it turns out it also served his neighbor's apartment.

However, you can tap it, by adding your own wires to the bundle. Usually when it's a simple 2-black and 2-white (or 3-3, 3-4 or any nearly equal number) in a bundle, you can count on the whites being actually neutral. So voilà, we have found where to attach your fan's neutral wire: add it to the bundle.

We don't quite know what those black wires are. They may be always-hot; they may be switched-hot off a mystery switch. It would help if we knew where the onward wires go, because builders don't install wires unnecessarily. Regardless... these are the only "hot" wires in the box, so they are our only choice for the fan. The fan's black wire gets added to this bundle.

That's the best we can do. Expect one of your do-nothing switches to start doing something. This may not play well with the remote.

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