Finding the beginning


Old 07-05-06, 04:22 PM
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Join Date: Nov 2002
Location: Orange County, CA
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Finding the beginning

I am re-wiring my 1968 house from AL to copper. There is a lot of exposed AL Romex due to the master bath remodel so I want to replace it all while it is "easy" but now I have found that the circuit the master bath light is on also contains other lights throughout the house, where the wiring is not exposed. I found this out by flipping the breaker to the lights in the master bath and then testing what other lights did not work anymore.

I have excellent attic access to most of the wiring but my worry is that if I replace the AL wiring in the master bath and terminate it there, the AL wiring to the remaining lights will not have power.

Trying to figure out the wiring scheme of the original circuits seems very difficult since not all the cables are in the attic, some go into walls for switches. I can tell the lighting cables since they are #12 AL and the 20 amp wiring is #10. But there are two baths and each uses a fan with a switch next to the light switch. Tracing is this cable and trying to figure it what is going on has got me stumped.

I thought I could just remove the AL cables in the master bath and trace the cable that is supplying power to the master bath backwards until I got to a lighting box (maybe the guest bath for example) in the attic. Then just disconnect that cable out of that box which would leave power to the remaining circuit. But if the master bath is in the middle or beginning of the circuit then I am without power in the remaining parts of the circuit.

All that said to ask a probably dumb question: how can I find the "beginning" of a circuit?
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Old 07-05-06, 04:50 PM
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The best approach would be to abandon the existing aluminum wire and run all new copper. Depending on the local codes, extent of remodeling, and number of circuits you are already planning to replace you may have to anyway. Certainly it would be the safest choice.

Since you have good attic access you should be able to drop cable to the existing outlets. The aluminum wire only needs to be pushed out of the boxes.

At the breaker box you will almost certainly need to remove a square foot or so of sheet rock for easy access. If you plan to reuse the boxes you can cut a small hole above to fish the wire. If you don't want to make a bunch of holes and the boxes are nailed to the studs you could cut the nails with a Sawz-all (Tm) and remove. Use the hole to fish new wire then install "old-work" (AKA pop-in) boxes to replace the existing boxes code permitting. In this case instead of running through the wall to the next box you'd return to the attic and then down to the next outlet.
Old 07-05-06, 06:47 PM
Join Date: Sep 2003
Location: Central New York State
Posts: 13,973
Originally Posted by Tyger52
I found this out by flipping the breaker to the lights in the master bath and then testing what other lights did not work anymore.
You should have done this a long time ago, like shortly after moving in. Everyone should know what is on each and very breaker or fuse in their house or apartment. This information could save your life.

After you figure out what is on each and every circuit, you have to then divide and conquer to figure out what order the wiring goes in. Unfortunately with AL wiring this is tricky. You must disconnect the wiring at each light, switch or receptacle, one at a time until you determine the first item on the circuit. Then one at a time until you figure out the second item on the circuit, then the third, etc.

Better yet, don't worry about the path of the wiring and just rewire everything on the circuit.

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