old wireing

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Old 11-10-04, 04:35 PM
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old wireing

i live in a 90 year old home. while i'm no electrician whenever i redo a room, i do a complete tearout and rewire all the outlets and ceiling lights as i go. normally adding one more outlet, or more to the new run.wherever i can i run new wireing. i don't change any thing just add. my question has to do with the wires running through the ceiling for the ceiling lights.most of the time the wires come from different directions. one may come from the ceiling while the other may come from the basement or from the oppisit direction. these are usually old wires,cloth coated, and never a ground. i assume they are grounded in the basement.when i replace a switch the two wires look the same are they. i'm sure the electrians back than knew what they were doing but i know i don't. any info on the methods back than might help me understand. any info would be appreciated. i find most of my questions already answered on other posts but not this one. thanks
 
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Old 11-10-04, 05:07 PM
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Given the vintage of your home you are most likely dealing with knob and tube wiring. This consisted of 2 wires, a hot and a neutral, there was no ground. The wires ran through porcelain insulators when they passed through a joist, the tube, and were supported on insulators, the knobs, when parallel to the joist.

The splices were made without boxes. The insulation was removed for a short distance and the tap was wrapped around the main run of conductor.

You may also be dealing with switched neutrals instead of the more modern switched hots. Do not switch the neutral in any of your wiring.
 
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Old 11-10-04, 05:08 PM
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Sounds like your house was wired before equipment grounding was invented.

I'm not sure exactly what your question is. You have two cables coming from two directions. Most electrical boxes in most houses have the same thing. One cable supplies power and one cable takes power somewhere else. For a ceiling light that is controlled by a wall switch, it might be that one cable supplies power and one cable is a switch loop to the switch. Or it could be that the switch controls more than one thing. Or ... (there are lots of possibilities).
 
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Old 11-11-04, 11:39 AM
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these are usually old wires,cloth coated, and never a ground. i assume they are grounded in the basement.
Very bad assumption. They are probably not grounded. How could they be if there is no ground wire present?
 
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Old 11-12-04, 10:02 AM
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If you have the room down to the studs, now is the time to bring the electrical up to current code, not just replace the wires. The circuits is probably grossly overloaded by todays standards and will blow circuit breakers due to the increased demands of todays electrical demands. I suggest you add outlets so that at no point along the wallspace, are you more than 6ft away from an outlet. It will be much easier to make these changes now as opposed to after the walls have been closed back up.
 
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