I have a tangle of BX cable in my front hall ceiling that I couldn’t leave well enough alone…. I took down the fixture because I wanted to see if the original guy had a three way switch or not. I have a dead switch in the upstairs I was
Long story short is that I figured out this fixture (I think) had a switched neutral. I can’t revise this situation without fishing a new wire. (one of the wires on the switch leg is trimmed back into the BX, its insulation is cracking off, and I don’t have enough slack to pull it through. The prior electrician managed to use this as the neutral and switched it.
I tried to put it back the way it was (the ostritch move) and now the bulbs glow dimly when I throw the switch.
Questions:
Physics: Why the hell would it glow dimly?
Moral: Is a switched neutral inherently dangerous, or will it just not work well?
Philosophical: I think I’ve resigned myself to pulling new wire (I may even attempt to get a wire upstairs for that 3 way switch); but is there any way to fix that dim glow in a safe manner?
As usual, any replies greatly appreciated (and usually damn helpful)
Ben
Replies
Ben,
Thats all messed up. I wouldn't have any idea why the bulb is dim unless the shield on the bx is being used as a neutral and is not as solid as it was before you took things apart, and the 2 wires probably are are hot and traveller. Either way you need new wires buddy.
Physics: Why the hell would it glow dimly?
Because it's not getting 120V across it, for some reason. It's a little hard to tell from the brief description what this thing looks like, but some of the voltage that should be across the lamp is instead across some other point in the connection. 'maybe a bad, high impedance connection that resulted when you put things back together (like a crack in the wire). or the circuit be be shorting out to the BX shield, and completing through a lousy ground rather than the neutral. Both of these are not safe; could cause a fire, or a shock.
Moral: Is a switched neutral inherently dangerous, or will it just not work well?
It's dangerous. With a switched hot, when you turn off power to the fixture, the firxture is dead -- no voltage. With a switched neutral, when the switch is off, the whole fixture is at 120V: waiting to shock some unsuspecting person replacing the fixture, or even just replacing the light bulb (since this makes the outer diamter, screw-thread terminal of the light bulb electrically hot).
A friend of mine was complaining about getting a tingle off a light fixture in the basement. It was a metal bullet light with two bulbs. The whole thing was shot loose. The socket shell was laying against the metal shade. And the metal was switched. So when the light was off there was 120 volts on the fixture.
Sounds possible that it's in series with another something else.
Switching neutrals is a poor idea.
And lastly I hate to say it but... it sounds like you are in over your head if you cannot figgure the circuit out. Money spent on a qualified electrician would be good insurance at this point.
If it was just a case of a switched neutral the light would still be working at full power. The possibility that the BX armor was used as a conductor is pretty scary but not entirely without precedence. You haven't provided enough details and I'm not sure if it would help much if you had.
On the face of it it sounds like you need to rewire part of this circuit. Some thought might be given to what else may be miswired in this house. What you need is a pair of eyes that know what to look for both for this small problem and to inspect more generally. My considered advice is to call in an experience electrician.
I agree with 4LORN1. The deteorated condition of the conductors and your not being able to understand why the bulb is dim indicate that an electrician should look at this. This is not a slam or anything, but you could have other problems with the wiring, and anytime you are not geting full voltage to something like a light bulb there is a serious problem which could lead to fire. And I HAVE seen all manner of improperly and dangerously wired circuits which are sometimes hilarious and sobering at the same time. Bozo circuits, I've seen a bunch.
No insult taken on suggesting I get an electrician. I just can't figure out why the lightbulbs were only glowing faintly. Maybe I'll check the BX jacket for voltage. The circuit is off - I wouldn't leave something like that live.
The wiring is hard to describe. The switch, for instance, was a single-pole switch hooked up to two wires of a three-conductor armored cable; the third was tied to another neutral in the switch box. The ceiling "box" (actually a cast iron fixture for holding the BX) has a cable with a live hot and neutral, and then this single two-conductor cable where only one of the conductors (black) was hooked up; I think it was to the neutral (this BX is not the same three-conductor cable which comes out at the switch). The other conductor in the BX has been cut back; if you test it, no power is supplied with the switch on, and I couldn't get continuity across it, because I'm assuming its not hooked up to the switch of course. Plus there's the porch light and porch light switch BX coming to the same place as well; they work fine if you hook it up with the live BX supplying power. I was wondering if someone wired it up (as it should be, seeing as it's a hallway at the bottom of stairs) to a three-way circuit with my (now dead) switch at the top of the stairs (that one has 2 BX cables feeding it, no power in either) and then ran a run to where the fixture is. My guess is that once it worked as a three-way and then someone messed around with it and jury rigged it to only work with the downstairs switch. A good electrician after looking at it could probably figure it out in three minutes. I think his answer would be rip it out and rewire it.
I think I'm just going to fish new romex to the switch and be done with it. I'd like to hitch up the second floor switch as well, but I don't know if my fishing (and plaster patching) skills are up to it.
Thanks for the help
Ben
Edited 12/2/2002 12:42:06 AM ET by Ben
As some else mentioned it sounds like the lights are in series with another load. But that is pure speculation without seeing the actual situation.
" The ceiling "box" (actually a cast iron fixture for holding the BX) has a cable with a live hot and neutral, and then this single two-conductor cable where only one of the conductors (black) was hooked up;"
Let me tell you what I found in my house. I have a open L shaped living room/dining room with the kitchen being in small leg of the L.
After living in the house for 15 years I was painting in the living room and had the coverplate of a bank of 4 switches. I brushed against one of those switches and the kitchen light blinked.
If I did not remember something in the back of my head I would probably still be trying to figure out what happened. I remebered a couple of days before I moved in one the electrican assistants mentioned that the kitchen circuit was nto working, but that they would fix it.
Well they "fixed it". Power feed to the switch for the kitchen light. From the switch to the light 14-3 was run to the light so that it has both a switched and hot lead. Then the hot was run to several other places including the back door where there where several switches including a 3 way siwtch. The other end of the 3way was in the living room box of 4 switches.
What happened was that a nail has been run through the 14-3 shorting the ground and neutral to the hot. So they just cut the ground and neutral wires at both ends of the run. Then at the kitchen light they tied the neutral to the ground wire.
The "ground" wire was ground because it was connected to the ground wire in the living room box. That ground wire was pushed back in the box and was loosely touching the ground wire of a completely different circuit that was also in the box.
It sounds like they might have done something similar here. They picked up a neutral from a different circuit or using the grounded bx as the return.
> As some else mentioned it sounds like the lights are in series with another load. But that is pure speculation without seeing the actual situation.
It's in series with something. If the something is another legitimate load, like another light bulb, that's not a useful installation, but at least not particularly dangerous. If the other something is a bad connection, corroded or whatever, that's much more dangerous. What is happening is that the amount of current running thru the dim bulb times 120 minus the voltage observed at that bulb is turning into heat wherever that other something is. If it's a bad splice in a box that somebody stuffed full of newspaper and plastered over, it can burn the place down.
Piecemeal fixes to wiring like this are a bad idea. Charge up all your cordless drill batteries, then early Saturday morning take out all the fuses, turn off all the breakers, open every box in the electrical system, and figure out exactly where everything goes. Draw and keep a diagram of what you find. Then put it all back together right, clean and tight. That makes for a long, boring Saturday, but at least you'll know what you're up against.
-- J.S.
Also, please don't think I'm ignoring Mark and 4Lorn's opinion about getting the whole system looked at by a real electrician. Much of the wiring is (relatively) new and fine; the old stuff I do look at can be scary.
I'll get a crowbar in that wallet, loosen it up a bit, and find someone to call when my money situation gets a bit better.
Now let me wander over to the Arc-fault Circuit Interrupter discussions so I can see if they'll help in the meantime....
If it was just a case of a switched neutral the light would still be working at full power.
Nope, that's dead (so to speak) wrong.
The outlet will have full 110 v potential, but the light won't light until the circuit is completed. And, the light socket won't kill anyone until they touch it (thinking it's dead because they just turned the light off at the switch) when they are grounded.
I consider a switched neutral to be a dnagerous wiring defect for that reason: it fools people into thinking they are safe at the very time they are potentially at high risk.________________________________________________
"I may have said the same thing before... But my explanation, I am sure, will always be different." Oscar Wilde