I want to add an exhaust fan to my bathroom. Do I run power from the light switch to power the fan or do I run power from the light box. Thanks as of now there is a single pole do i use a double pole switch?enter image description here]enter image des(https://i.sstatic.net/WNtCT.jpg)![enter image descriptihere](https://i.sstatic.net/J3Euy.jp![enter image description here![enter image d)

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    Can you post photos of the insides of the existing boxes please? Commented May 21, 2020 at 11:43
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    My wording is wrong I basically want to add the exhaust fan and have the light and the fan on the same switch so they come on at the same time Commented May 21, 2020 at 13:52
  • The existing wiring may decide what you do depending on your ability’s and if you can pull new wiring. The easiest method would be to add the fan to the light. But as others have said then the fan only works when the light is on. To provide how to do it we would need to know where the feed for the light is. Is it in the light or at the switch. If there is only 1 cable with 2 wires and possibly a ground at the switch location the feed is at the light, multiple cables at the switch the feed probably at the switch. Adding a second switch will require adding a new cable unless there is a spare.
    – Ed Beal
    Commented May 21, 2020 at 14:04
  • I dont mind the fan working with the light as this is a bonus bathroom with not much use. Commented May 21, 2020 at 14:23
  • It depends on how the wiring is arranged now. "From the light" is safer. Commented May 21, 2020 at 18:28

1 Answer 1


Answer from the UK but the principles should apply wherever.

You usually want switched live, permanent live and neutral (+ earth) going to the fan via a three-pole isolating switch. The permanent live is optional but lets you use a fan with a timer or humidistat that runs even when the light is off. The switch allows you to work safely on the fan without turning off power to the entire house and lets you turn it off temporarily if the fan ever breaks while still being able to use the light. The isolator would typically be located high up on a wall or in the ceiling, out of reach of bumps and splashes, and less intrusive visually.

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    Usually one turns off power at the breaker, not the switch, before working on wiring at a fixture. It's way too easy for you (or someone else) to bump the switch or turn it on out of habit to rely on just the wall switch to prevent electrocution.
    – FreeMan
    Commented May 21, 2020 at 12:22
  • @FreeMan in the UK the isolator switch for the fan is typically located in the ceiling or high up on a wall somewhere between the light switch and the fan. Some of them can even be locked for extra safety. The situation you describe won't happen.
    – Carl
    Commented May 21, 2020 at 14:50
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    Fair enough. However, I see no indication that the OP is in the UK. (Well, I didn't click through to read his profile...)
    – FreeMan
    Commented May 21, 2020 at 14:57

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