Electrical Rewiring Question I'm pretty sure that I'll be fine with this, but I thought I'd ask just to be sure that I don't miss any got ya's.
I'm adding a new ceiling fan and in order to do so, I need to replace the box with one with proper fan support. While I'm at it, I figure that I would remove some old brittle BX and cloth covered wiring just to get things updated. Currently, there is a BX cable from the breaker panel that goes up to the 2nd floor as the power source. From there, it branches out to some lights, outlets, and smoke detectors. This circuit goes everywhere because of the smoke detectors and eventually ends up back down in the basement smoke detector.
So, I was going to abandon the BX that goes from the panel to the 2nd floor and just run a new cable from the panel to the same circuit in the basement. (i.e. the smoke detector, or something else.)
My question is this... Are there any "got ya's" that I need to watch out for when doing this? The only thing that I thought of was to watch out for GFCIs in the circuit as I don't want to be powering them from the load side when I move the power source to this circuit.
Any advice would be appreciated. Thanks.
1.) With regards to the soon to be abandoned BX from panel to 2nd floor, are you planning to only disconnect and cap it in the panel or also disconnect it at the junction box from which it currently branches out ? Regardless what the code may say about it, I would consider it a lethal trap to keep the abandoned BX cable "hot".
2.) Perhaps even more important is the question whether or not you know for sure all the wire sizes used in that circuit. The "goes everywhere" part sounds like you may not. Since smoke detectors are minor loads I would be worried about someone (in violation of the code) having used a smaller wire size between two alarms. If you now reverse the circuit (instead of smoke detectors last, it is going to be smoke detectors first) you may give those sensors something to detect (because of over current in the undersized wire).
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1.) I would never leave it energized. It will be removed as far back from both ends as I can get it and then abandoned in place.
2.) I do know how the wiring goes as I've been tracing it out over the last three weeks. It only goes everywhere because the smoke detectors were added later. If it were done today, it would make no sense to send power to the 2nd floor only to then come back down to the basement afterwards.
You are also correct about the wire sizes. This circuit previously had a 20A breaker, but I've since changed it to a 15A breaker since most of the wire was 14AWG.
An old branch circuit that runs up & down and all over the house - one that some had put a 20A breaker on - is already overloaded. Don't add any more loads to this circuit. You should be looking to 'split it' into two circuits. Since you can apparently wire a new circuit from the breaker panel; do so. Leave the old one in place and put half of its loads onto the new circuit. Or even better; abandon it in place as you say; and wire two new circuits splitting the loads between them.
The other gotcha, is brittle old wiring. Once you touch it - its history. The insulation will break off no matter how much you don't want it to. It will become more a fire hazard the more it gets touched; and simply the more time that passes. Time to fix it.