Rewiring bathroom - need basic help.

Old 04-24-10, 05:45 AM
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Rewiring bathroom - need basic help.

My wife and I are redoing a bathroom. Our house is old and has the original wiring with 2-prong receptacles throughout. I want to re-wire this bathroom now, with plans to do the other rooms one at a time as we can. This is my first wiring project, but I want to do it myself and learn.

I have an electrician who is going to install a new breaker box and ground rod and get that all up to code.

All drywall (wall and ceiling) and tile is out of the bathroom. I have an attic.

It's a small bathroom with 1 switch controlling 1 vanity light, 1 switch controlling a ceiling heater, and 1 2-prong receptacle. I'm going to install a new vanity light, exchange the ceiling heater for an exhaust fan, and replace the old 2-prong receptacle with a GFCI receptacle. I plan on using a single 20-amp circuit.

Can someone give me a basic diagram for wiring this? Is there any reason not to use one switch for the light and exhaust fan to ensure the fan gets used every time someone bathes/showers?

This might seem really basic, but like I said it's my first wiring project so I want to get it right.

Thanks in advance.
Old 04-24-10, 09:13 AM
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There is more then one way to wire this but what I would do is bring in a #12 from the service panel to a double gang switch box. From there I would continue it on through the vanity light switch to the vanity light.

I would run a separate cable from the switch to the GFCI receptacle and a Separate cable to the fan. This way only the receptacle is affected if there is a trip. You will still have lights.

That is basic but I would refine it a bit. I would run 3-conductor cable to the light instead of separate cables to the light and receptacles. The red of the three conductor would be from the switch and the black from power in. The 3-conductor cable would go to the light. Then the red would go to the light the black would go to a two conductor cable to the receptacle.

I would also run 3-conductor to the fan in case you ever wanted to change it to a fan and light.
Old 04-24-10, 09:16 AM
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It IS really basic and I hope that you have purchased a couple of good books on residential wiring and read them cover-to-cover before starting to pull any wire. One book that I always suggest as an absolute MUST for the DIYer wanting to do electrical work is Wiring Simplified. It is available in the electrical aisle (don't look for it where all the other books and magazines are located) at most mega-mart homecenters and costs less than $10 as I recall. It is also available from many on-line merchants such as Amazon.

Use Wiring Simplified as your "bible" telling you the "why"and get a second book (there are many) that has pictures showing the "how and where" and you will be fine. If you have any specific questions that you cannot find the answer in Wiring Simplified don't hesitate to ask it on this forum.
Old 04-24-10, 10:57 AM
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I agree with Furd that if one is (especially)a novice at this, you really need to understand it first. Often, a person can learn just enough to be dangerous, as the expression goes, if you do not fully undestand all the ramifications.

Here is a case in point regarding me, and I even know a little bit about the subject: (Other regulars here will remember this, I am sure). I was green on a "shared neutral circuit". And after posting here, it was pointed out that I had to return the wire I removed from the opposite leg, ASAP. Here I thought I was doing the circuit a favor by eliminating what I thought was a potential short, that might cause 240 in a 120 circuit, and ruin the lady's tv, that already got wrecked twice befiore (hence my service call -remember that story, guys?)? Instead, I learn here that it turns out that if both circuits are used at once, you can overheat the shared neutral wire, if the 2 hot wires are on the same leg!

In a bathroom you want to understand why the need for a GFCI, and when and why you need to protect the load side.

You need to know if you put a fan/light in the shower how to handle that.

The bottom line is - you need to understand not just how to do something by what a book looks like, but know why you have to do things certain ways. With the rest of the house, there will be other applicable things, such as AFCI's, how you balance the load at the box, how many things to put on a circuit, and what those things should be, what has to be on it's own circuit, anticipating the draw on a new circuit so that it is say 15 or 20% under the breaker size, when good places are to have 3 or more way circuits and how they are wired, when to run 3 wires w/ground rather than 2 wires w/ ground, completing a circuit so that 1/2 the duplex outlet can be switched, what a true backstab connection is compared to a back insert for the wire that is not really a backstab, when and where to wire staple and if necessary, where to put junctions, how many wires per, wire sizes, pigtailing, gounding of fixtures and boxes.......just a lot of things.

If you did something not up to code, and sold your home and it caused a serious problem to someone else, maybe you could even be sued.
Old 04-25-10, 05:55 AM
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Yes, you would typically want the fan to run whenever someone showers, I will give opinions why you may not want the light switched with thr fan. If you are only dressing or putting on makeup or brushing your teeth you wouls not need the fan. Using the fan ejects the heated or cooled air from the house and increases your energy bill. You may also want to leave the fan on to make certain all the humidity is gone or after certain dinner items.

You can get exhaust fans with a humidity sensor built in so the fan will turn on while someone showers.

I hope you meant that you were going to discontinue the use of all the old wires.
Old 04-25-10, 06:04 AM
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Originally Posted by pcboss View Post
I hope you meant that you were going to discontinue the use of all the old wires.

I was wondering about the fan running every time the light is on. It could be an issue, especially in the winter. I guess a separate switch or humidity-sensing fan is the way to go.
Old 05-05-10, 11:01 AM
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you can also get a digital timer switch w/ presets for the ex. fan


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