Replacing a single light fixture that's controlled with two switches. The light box has a standard black/white/ground supply wire. While installing I found that the white wire was actually hot (and marked with black tape) and the black was neutral. The only issue was the only way I could read 120V from the hot wire was to ground the circuit. This seems odd to me as none of the three way wiring diagrams I've seen seem to require the neutral being grounded at the fixture. The reading from hot to neutral was 60V - not sure if this means anything or not.
Is this OK or is there something I need to look into here?
It is legal. Romex comes with one black wire and a white wire. You assumed the white wire is neutral. It isn't. It is one of the two wires needed for the switch. The black tape is to tell you that the wire is the return from the switch and not a neutral.
It doesn't sound okay to me. It sounds as though you have no neutral at the light fixture. The feed for the light fixture should come from one of the switches. Open them up and see if you have a neutral in there. The feed for the circuit should also come into one of the switches. It could be the same switch as the one that contains the light feed or the other switch. Check to see if you have juice between the white and the black circuit feed. I suggest using a pigtail light socket with a light bulb instead of a digital meter.
Another possibility is that this set-up is wired using only two wires instead of three between switches. In that type of operation the neutral and hot rotate getting turned off depending on the positions of the wall switches. Try flipping the switches and see if the polarity changes and you get 120 volts. This is not the proper way for three-way switches to work as the hot is off only 50% of the time and the neutral is off the other 50%.
Did the old light fixture work before you replaced it? If so how was it wired?
Actually the NEC says you use the white, reidentified another color for the feed to the switch and the switched leg is the black. That way the luminaire installer is presented with a black hot and a white neutral. 200.7(C)(2)
The wring to the first switch box should be an un-switched hot (black), an un-switched neutral (white) & a ground wire to the switch & the box (if metal) .
The wiring from the first switch box to the second switch box should be two switched hots (black & red or re-indentifed white), an un- switched neutral (white) & a ground wire to the switch & the box (if metal) .
So one needs 4 conductors (including the ground) between the two switch boxes....here's where some people either get confused or cheat. Ideally you use a three wire romex (black, red, white, ground) or a double run of 2 wire Romex.
From the second switch box to the fixture box you should have a switched hot (black), an un-switched neutral (white) & a ground wire to the switch & the box (if metal) .
The setup you describe (if I'm understanding it) seems a little off.
Is the circuit wired with Romex or single conductors (knob & tube OR wire in conduit)?
Maybe the circuit existed as a single switch & the three way part was added later.
Be careful, because of the limitations of 2 wire Romex systems, some people take shortcuts on rewiring or additions that can leave you with less than safe situations.
per John's comments a light bulb is often better than a meter
The 60v reading might be a result of a poor connection somewhere or a digital meter giving a false reading reading.
What it sound like, as mentioned in one of the replies is that black and white wires go from the ceiling box down to the switch. One of the wires is the 'live' feed in and the other is the 'switched live'.
Consequently when the switch is 'on' electricity flows down to the switch through the switch and back up to the 'hot' side of the light fixture; and the light goes on.
Reading 60 volts may be meaningless; even cheap modern digital meters can pick up voltages due to capacitance between wires etc. A much better way to test is to use a regular bulb.
Nothing should be wired to the ground except metal parts of wiring boxes, ceiling boxes, metal roses etc. the ground is a safety wire.
The ground can, but only 'momentarily' be used for testing; for example put the test bulb between a wire and ground; if it comes on all the time (with circuit breaker for that circuit on) it is a 'non- switched live'. If it goes on and off as you operate the switch it is a 'switched live'.
Then turn off the circuit breaker and wire the switched live to the light fixture (or fixtures. Cos some rooms have two or more lights controlled by the one switch!) Turn breaker back on (or reinsert fuse) and test.
Thanks for all the replies. Looks like a previous post of mine got lost. Anyway...
I am going to pull out each switch and examine to see if I can determine exactly what's going on. I will take pictures if I can't figure it out and post back.
One followup question -
If I am to understand what might be happening is depending on which switch is switched on, either the white or black wire could be the hot wire. Is this accurate?
I doubt it was ever a single switch. It's a kitchen light and (with the exception of the bedrooms) EVERY light in our house is on a 3-way circuit, including two four ways. As far as how the circuit is wired (BobK207's comments), everything is wired with standard wiring. I'm not sure what Romex is. The supply wires in our house are black/white/ bare ground 12 gauge copper covered in what appears to be metallic sheath (it's silver in color).
Anything is possible. At the fixture, you should have an unswitched Neutral regardless of what color it is. You should be able to determine which wire because it will give you continuity to the ground conductor or metal box. Only ungrounded (hot) goes through the switches, then returns to the fixture. With a light bulb pigtail, test between the hot return wire from the switch and either ground or neutral, it'll light with the switch "on"
I composed a reply to your comments but lost it when my PC froze. :(
I'm pretty sure from Doug's original post there is only a white (tagged with black) & a black wire in the fixture box under consideration.
If Doug's only got two wires in the box & the tagged white is hot (& switched) and the black wire is in fact the neutral (0 volts to ground) ...then he's got some color coding issues.
I'm not sure I'm understanding your comment
and white wires go from the ceiling box down to the switch. One of the wires is the 'live' feed in and the other is the 'switched live'.
Consequently when the switch is 'on' electricity flows down to the switch through the switch and back up to the 'hot' side of the light fixture; and the light goes on.
House was built in 1963. Again, not sure what the cable is called, sorry for the ignorance. Descriptions I found on the internet of BX cable appear to have a solid metal sheath. This has more a a cloth- like metallic texture (i know that's a bad description, sorry). I can't get pictures until tomorrow evening so I will post back then. Really appreciate everyone's help on this.
I've got the boxes open and am trying to sort everything about. I'm about to get a light rig out to check for current, but thought I'd go ahead and post this.
Switch 1 - description:
formatting link
CHAOS - this is the best way to describe what's going on in the first box. There are three 3-way switches in this box all powering different lights. The switch on the far right, off the edge of the picture powers the fixture in question. There are seven - SEVEN - cables (all with their own black/white/bare grd coming into the box). One of the wires coming in goes to the Kitchen light switch's hot/ neutral connections. The third pole on the 3 way switch comes from a pigtailed collection of 5 black wires, three of which head back out of the switch, and one of which actually heads to the third pole on a second 3-way switch (the switch on the far left - which powers the family room overhead light), and the last of which heads to the switch in question. As I was pulling the switch out of the box, this wire broke and now the light won't work.
Switch 2 description:
formatting link
2 Black/White/Bare Grd wires into box: Black and white from right side go to hot/neutral on switch. Black from left side heads - by itself - out of the left side of the box, and re-enters (Here I am making an assumption that this is the same black wire) in the back of the box below where it originally came in, and connects to nothing (strange, never seen this before). The white wire is pigtailed (to add length) and connects directly to the single pole on the switch.
After looking into the big switch box I was able to determine that the middle switch is not connected to the other two switches with the exception of a pigtailed white wire.
Further, I got a light out and tested the circuits. Huge pigtail of 5 black wires in the first box is hot, regardless of any switch's position. That means that the third pole on the first three way switch is always hot. I could not read any current nor light the bulb since the third pole disconnected from the pigtail in the first box, nor could I read any current or light the light in the second box.
I'm having trouble picturing in my head how this switch is functioning. Any ideas?
One more update before I goto bed - got the broken wire fixed. When the light fixture is off I read current across both the hot/neutral combo on switch one, third pole/neutral combo on switch one AND black/ neutral combo on switch two. third pole/neutral combo on switch 2 does not read when the light is off, nor does the unconnected black to ground or neutral in switch 2.
When you started this project, you were replacing a fixture. Was the existing fixture and all this switching working properly at the time? You clearly have a mess there as it appears that three sets of three way switches were wired all illegally using multiples of two wire cables. Any suggestions I could give would be wags without knowing where each conductor comes from and goes to. I would, at this point get an electrician on the job to do this.
"Working properly" can mean many different things. Yes, everything was "working" and it still is. The question I was seeking an answer for - I guess - is why I needed to ground the fixture out to make it work (and whether or not such practice causes a safety hazard). I still don't know why I need to ground the fixture out. I can't quite figure out how the switch is working with two hot wires leading into one three way switch. Hopefully the electrician can "shed some light" on it.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.