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Three sets of wires come into our overhead light electrical box. Two with white, black, ground, one with white, black, red, ground. Which wires do we use to hang our fan/light? It comes with white, black, ground. Why are there so many wires into one box? We don't have an electrical tester to see what's live.

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    Those other wires and cables have other jobs. It is critical to know how it is hooked up now. It would also be helpful to see how things are wired in the switch box(es) from which this fan will be controlled. – Harper - Reinstate Monica Aug 12 at 22:19
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    Can you post photos of the inside of the box? – ThreePhaseEel Aug 12 at 22:36
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    You can get electrical testers (a basic set doesn't cost much) and learn how to use them, or hire an electrician. DIY without proper tools is dangerous. – manassehkatz-Reinstate Monica Aug 13 at 0:46
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Figure Out What You Have First

The instructions below are based on a typical configuration. This is very likely to be the case if:

  • The 2 Black/White cables are currently connected together
  • Power is coming in on one (and if you disconnect them, only one, of the black wires). You need a tester to verify this before continuing.

If these 3 cables are all sitting capped (wire nuts) in the box then this will be tough to figure out. More typically though, one set is "in", another is "out" (to other devices sharing power) and the third is "switched". All grounds go together, so they can be ignored for purposes of figuring this out. A typical configuration is:

In - Black, White

  • Black = Hot
  • White = Neutral

Out - Black, White

  • Black = Hot
  • White = Neutral

Switched - Black, White, Red

  • Black = Hot
  • Red = Switched Hot 1
  • White = Switched Hot 2 (note, this one of the rare situations where White is not Neutral) or Neutral in the Switch Box (required in most places in new installations)

If that's the setup, it is designed for a combination ceiling fan + light with separate switches for fan & light. That used to be very common. Now with inexpensive remote controls it is less common.

New Fan

  • Black = Hot or Switched Hot
  • White = Neutral

Connections - Using a Single Wall Switch

  • All Cable Hots (Black from all 3 cables) together
  • All Cable Neutrals (White from In & Out) together plus white wire from fan
  • Switch connects to Hot (Black) and Switched Hot (Red)
  • Cap the Switched Cable White wire on both ends - you're not using it right now.
  • Red (Switched hot) to Fan Black wire.
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You probably have a supply line in, a traveler out to the switches, and two switch legs (red and black) coming back.

This is an educated guess. You absolutely need to get an inexpensive tester and find out what is hot. Trying to install your fixture without it is dangerous.

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