Perplexing Situation

[GilbeSpark]

Hey guys I ran into something today. I didn't have time to dive into it but I'm going back to fix it soon and I'm looking for a heads up on what to look for to speed the process up as much as possible.

Here's the situation: Attatched to a single pole switch is the black and white wire from the same piece of 14-2. At the junction box of the light where the "switchleg" is terminated, with the switch in the off position, the black wire reads 120v to ground and the white wire reads 120v to ground. No voltage from black to white but continuity rings out. When you flip the switch in the On position I get 120v from black to ground and 120v from black to white, 0v from white to ground.

Obviously there's at least 1 junction box inline from the switch location and the light box location, but what would cause the white to be hot when the switch is off and then get 120v from black to white when the switch is on? This was read with a wiggy type meter as well as a digital multimeter.

 

[nakulak]

switch is upside down and bulb is burnt out ?

(or maybe its a california 3 way ?)

 

[Rewire]

when you turn the switch on does the light come on?

 

[GilbeSpark]

The switch was not upside down and the bulb was not burnt out. The light in question was a fluorescent fixture. When the switch was turned on the fixture did come on and illuminate. The homeowner (my neighbor) said he had been replacing the light at least once a year for the past 6 or 7 years (since right after he hired an electrician to add in the light).

 

[electricalperson]

do you have a burned neutral on a backstabbed device? i had a similar problem 0 volts H to N 120 volts H to G and N to G. turns out there was a burned neutral and it was reading through lightbulbs, can it be a bootleg ground somewhere? if you have 0 volts from N to G its the same potential so maybe the neutral is being used as a ground somewhere?

 

[480sparky]

The neutral is switched, not the hot.

 

[electricalperson]

The neutral is switched, not the hot.

thats also another good possibility. probably the right answer

 

[Fulthrotl]

The neutral is switched, not the hot.

bingo. throw that man a cookie.

 

[GilbeSpark]

Then with the switch in the off position, what would cause the neutral to read 120 to ground?

 

[LawnGuyLandSparky]

With the switch off, you're reading the voltage right back through the load.

 

[electricalperson]

ken is the smartest electrician in the world. my post sounded ridiculos(sp) but maybe it could of been right

 

[Rewire]

I use to see alot of switced nuetrals on older houses

 

[480sparky]

Then with the switch in the off position, what would cause the neutral to read 120 to ground?

The voltage is available all through the circuit up to that point. If the neutral is switched, the circuit up to the switch is energized to 120v potential to ground.

Think of it this way: Take a 120v circuit through a load, and the neutral is landed on the neutral bar in the panel. Take the neutral off the bar, and you'll read 120v between the white wire and the bar, as well as 120v between the white wire and ground.

 

[electricalperson]

I use to see alot of switced nuetrals on older houses

i should of thought it was a switched neutral. a lot of the old houses have 3 ways wired carter style. hook up H to N to the traveler screws and send 1 wire from each switch to the light. switches neutral or hot depending on switch positions. pretty confusing to figure out when not familar with these kind of wiring methods

 

[PetrosA]

When you got 120V from the white to ground, was the fixture still hooked up or were the wires disconnected? Is the fluorescent light the only light on that switch? It would make sense that it's a switched neutral, but only if the fluor. was hooked up when you got that reading or a second lamp is also switched. Are you getting 120V at the switch itself with the lamp disconnected?

If you have all romexes and don't see any knob and tube, I'd say it's pretty unlikely that you have a Chicago 3-way (you only mentioned a 14-2 to the switch).

 

[GilbeSpark]

When you got 120V from the white to ground, was the fixture still hooked up or were the wires disconnected? Is the fluorescent light the only light on that switch? It would make sense that it's a switched neutral, but only if the fluor. was hooked up when you got that reading or a second lamp is also switched. Are you getting 120V at the switch itself with the lamp disconnected?

Wires were disconnected, the fluo was the only light on the switch. With the wires disonnected (fixture not hooked up) and the switch "Off" I was getting 120v on the neutral and 0v from H-N. When the switch was flipped to the "On" position the 120v on the neutral went to 0v, then I got 120v from H-N.

 

[Smart $]

Wires were disconnected, the fluo was the only light on the switch. With the wires disonnected (fixture not hooked up) and the switch "Off" I was getting 120v on the neutral and 0v from H-N. When the switch was flipped to the "On" position the 120v on the neutral went to 0v, then I got 120v from H-N.

Check voltage at the switch terminals (to each other and to ground) in On and Off positions... or better yet, turn off power, remove switch, and check continuity across switch in On and Off positions. You may have a switch that got the toggle reversed in manufacturing.

 

[Smart $]

Wires were disconnected, the fluo was the only light on the switch. With the wires disonnected (fixture not hooked up) and the switch "Off" I was getting 120v on the neutral and 0v from H-N. When the switch was flipped to the "On" position the 120v on the neutral went to 0v, then I got 120v from H-N.

Check voltage at the switch terminals (to each other and to ground) in On and Off positions... or better yet, turn off power, remove switch, and check continuity across switch in On and Off positions. You may have a switch that got the toggle reversed in manufacturing.

After further consideration I realized a reversed toggle cannot be the only problem with this circuit.

One thing that makes the solution eluding (for us) is how you are reporting the voltages. When you say you have 120V on the neutral (at the fixture?), you are not stating as to what the voltage is referenced. For a voltage measurement, you have to state the two test points used in the measurement. To this point you have not stated any of your measurements are to ground, or if there is even a ground available to make such a measurement.

In your one post you mentioned a j-box in line between switch box and fixture. Have you found this box and examined the connections within?

When reporting voltage measurements please specify location, position of switch, light on or off if connected, and voltage measurement to all available points... i.e. L-N, SL-N, L-G, SL-G, and N-G. You may also need to determine which side of the switch connections is line side and load side.

 

[Smart $]

...measurement to all available points... i.e. L-N, SL-N, L-G, SL-G, and N-G. ...

...and I forgot L-SL

Another way to measure voltages is to use an extension cord with verified L-N-G voltages. In doing so, be aware that you could possibly get 240V L1-L2 measurements (assuming a 120/240V service) between the two circuits. Though this method gives you more possible combinations of test voltages, it will be easier to verify hots are hot, neutrals are neutral, and grounds are grounded.