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2 circuirts using 3 wire romex?

Posted by capecodcook (My Page) on
Tue, Jan 23, 07 at 17:18

For whatever reason, the electrician involved in a recent kitchen remod used 3 wire+ground romex to wire from a wall switch to ceiling lights (we never specified two switches-have no idea how we ended up with 3 wire.) Later my wife decides she wants a ceiling fan in the kitchen. While trying to figure out how to get power into the attic to run the fan, I discover the 3 wire cable and notice that the red wire is totally unused, capped at both ends with a wire nut, one end in the wall switch box and one in a junction box in the attic. Can I use this extra wire as a separate feed, using the white wire in the cable as a common neutral? I would connect (pigtailing the switch) the red wire to black wire before the switch in the switch box and then run a regular 2 wire+ground romex cable from the aforementioned junction box in the attic to the box for the fan. The fan and the ceiling lights would share the white neutral in 3 wire cable. Total load would be 600 watts. This will obviously get power to the fan with minimum effort on my part, but is it code approved? Snaking an additional 2 wire romex cable down the walls of old houses is not real easy (I tried) and discovering the spare red wire was a godsend.

Follow-Up Postings:

RE: 2 circuirts using 3 wire romex?

You can use the free upgrade to feed the fan seperate from the light with the same neutral.
Thank the electrician. No one ever does.

RE: 2 circuirts using 3 wire romex?

I think the electrician was wise and responsible. I have done what he did many times. I recently wired a room addition for a friend. He wanted a celing fan with a light in the middle of the new room. He told me that he didn't want a separate wall switch for the fan. He said that he wanted the fan to come on with the light and that he would use the pull chain on the fan to turn it off. So I could have run just a 2-wire cable, but I ran a 3-wire cable and capped it off with wire nuts as did your electrician. I did that in case he ever wanted to have a separate wall switch for the fan. Guess what he wanted a few weeks later - a separate switch. Even though there was a single box for the light switch, he got one of those double swithes that fits in a single box, and he had the wire already there (the red one) to use to switch the fan from the wall.

Consider that situation. Before he added the new switch all the current to feed both the fan and the light was flowing in one direction through the black hot wire and the other direction through the white neutral. So the neutral was capable of carrying the current for the light and the fan. When he hooked up the red hot wire and put the fan on it with a separate switch, he didn't increase the load on the neutral; it stayed the same.

As long as the circuit is not overloaded, what you describe should work fine. It's no different with the neutral in the 3-wire cable than it is with the neutral in the cable feeding the switch box; it carries the same current that the neutral in the 3-wire cable will. In fact, for example, every wire in a 20-amp circuit has to be able to carry 20 amps. Think about a cable leaving a cirucit breaker - one that feeds a circuit. It has to be able to carry all the current feeding everything downstream from it.

Your electrician might have figured that you might eventually want a celing fan, and he might have planned for it.

RE: 2 circuirts using 3 wire romex?

while we are remodeling our house we plan on adding ceiling fans to 2 bedrooms and 2 in the living/family room. when i wire them, would it be wise to wire them that way in each room right from the start?

i am not the most knowledgable when it comes to electrical, but i know some... just to sum it up, basiclly the fan and the light would SHARE the white (neutral) and ground, then from one switch the BLACK (HOT) would go to the light and the RED (HOT) would go to the fan? sounds like less work to me!

RE: 2 circuirts using 3 wire romex?

Simple answer, Yes it would. Even if you never use it, the next owner might. Then they wouldn't have to pull new wire.

RE: 2 circuirts using 3 wire romex?

Thanks for the input guys. And I do thank my electrician. Not being one myself, I have found that what looks simple and obvious sometimes violates codes for good but not so obvious reasons. This time it all worked out.

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