3-way Switched Outlet Question

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  #1  
Old 03-13-06, 03:37 PM
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3-way Switched Outlet Question

Hi folks,

I'm replacing a wall outlet where one of the two outlets is always on and the other is 3-way switched.

I pulled the old outlet without looking at the wiring; I just assumed it would be easy. I decided to test conductivity on ALL combinations of wires to help me wire it up correctly but found that the two white wires actually lit my test light whether the 3-way switch was off or on!

Take a quick look at this simple diragram: http://www.tonytonini.com/outlet.gif

It looks like a no-brainer; the single black #1 wire is probably the 3-way switched hot wire and the two blacks twisted together are the always-on hot wire (where one sends power to the next outlet which I know for a fact), and the whites are neutral.

I looked at the old outlet which I removed and only the black side (brass side) tab was removed: makes sense.

But there's on problem ...when I connected the two white wires with my tester (#3 and #4) they lit my tester!! AND they conduct whether the 3-way switch in on or off. Also the two black wires produced a test light when the switch was "up!"

Doesn't that mean that when I turn on the breaker, they will cause a BIG problem since the whites are connected with the tab on the outlet on the white side?

Thanks for your thoughts on this in advance; I didn't hook it up yet till I hear something that makes sense.

-Tony

P.S. Here's what I found with my tester (touching two wires) with one of the 3-way switches in both positions; I left the other 3-way switch alone:

3-way up.........3-way down
2+3=on.............on
4+1=on ............off
4+3=on.............on
1+2=on.............off
1+3=off.............on
2+4=off.............off
 
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  #2  
Old 03-13-06, 03:45 PM
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Did you hook it up and try it? What happenned?
I don't understand your tests. Was the power off or on? What type of tester were you using?
 
  #3  
Old 03-13-06, 03:49 PM
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Forget your continuity tests they are meaningless.

Your job is to connect the wires to the new receptacle the same way that the wires were connected to the old receptacle. Too bad you didn't look at that wiring before you removed it. You have now learned a valuable lesson.

Your drawing makes absolutely no sense.

Tell us ALL the wires in the box. Tell us how the wires are or were connected to anything, to the best of your memory. To each other, to the receptacle, etc.

Also tell us where these wires come from. Are there cables? Is there conduit?

The most likely case operation is to connect the white wires to the silver screws, and to connect the single black wire to one brass screw, and the two black wires that are together to the other brass screw (with the tab broken).

However, my concern is that there are other wires you haven't told us about.
 
  #4  
Old 03-13-06, 04:17 PM
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Yes,

The tester I used is a simple light with the two prongs you touch to each wire (or push into an outlet) to see if 120 volts is passing thru or closing the circuit: the light turns on if it is.

If you pop the cover off a household electrical box and remove the outlet itself you have 4 wires: 2 white and 2 black (and two grounds). Now if you take the tester and touch a black wire (which is hot) and a white wire, the tester LIGHTS UP which shows you have a complete circuit and juice (110v). If you connect two whites they do not light up; if you touch the two blacks, they do not light up. I assumed this would be evident; sorry I didn't explain it in my original post.

Now when I touch the two whites, they light the tester. They also light the tester with two blacks (numberwed in the diagram). Then I tried every possible combination and the results are in my original post.

ALL the wires in the diragram ARE represented. The drawing is that of the outlet box in the wall with two 14/2 wires coming in at the bottom and one 14/2 coming in from the top but it only has the black wire in it.

I'm not sure why the drawing doesn't make sense; it is of the the 4 wires that are in it. They are clearly labeld black and white.

They are the 4 wires that were each connected to the 4 ports on the 15 amp outlet (2 white and two black).

I don't know what else to say. I supose I could get a photograph but it wouldn't be easy to see the wires.

I am fairly confident that hooking up the whites and blacks in the normal way will work, but I'm asking why two whites would conduct 120 volts.

Lee mw put it this way: If you diagrammed how to connect a 3-way switch to 1/2 of an outlet and the other 1/2 of that general-purpose 15-amp outlet is always powered which also sends non-switched power to the next outlet in the room, why would the two whites conduct?
 
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Old 03-13-06, 04:29 PM
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Your testing method is flawed. You are seeing voltage on a white neutral line because the current is flowing through a device. Disconnect ALL loads from the entire circuit and you will see nothing through one of the white lines.

The connections as I have outlined ans as you suspect are correct.

Now as for your wiring, you have a problem. Whoever wired this was cheap or lazy or both. They did not buy and use the proper cable, that being three conductor. Instead they used two pieces of two conductor.

If the receptacle box is plastic, this is not so bad. However, if the receptacle box is metal they have created an unsafe situation, which I urge you to fix. You should redirect the cable containing the single black wire to go through the same cable opening as the power wires.

Depending on the wiring, you may even be able to fix the wiring at the three way switches. Either way, I urge you to fix this, as what you have is not good.
 
  #6  
Old 03-14-06, 04:18 PM
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Well, I decided to hook up the 4 white and black wires in the traditional way with the tab removed from the black (brass) side and everyting works perfectly. There is no tripping of the breakers.

So, the wiring was correct (in the black wand white respect).

I just don't know why I was getting current when touching the two white wires (and then touching the two black wires depending on the 3-way switch).

Can anyone tell me why this is the case?

After connecting the receptical, putting in my tester into the two whites no longer lit up. BUT the two blacks did. ...which is ANOTHER mystery.

-Tony

P.S. The place is empty, so I thought there was no load in the circuit, but the hard-wired smoke alarm may have been in the loop. Does this change anything?
 
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Old 03-14-06, 04:33 PM
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As I stated, your testing method is flawed. You were reading current flowing through a device. In this case it would be the smoke detector, but it could be any load. A lamp plugged in, a hardwired lamp, an appliance plugged in.

Now please fix the problem with the wiring that I identified. Even though everything works, you have a problem that should be addressed.
 
  #8  
Old 03-14-06, 04:44 PM
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> I just don't know why I was getting current when touching the two white wires
> (and then touching the two black wires depending on the 3-way switch).
>
> Can anyone tell me why this is the case?

What is the question?


> After connecting the receptical, putting in my tester into the two whites no longer lit up.
Obviously they are electrically connected by the receptical and have the same potential.


> BUT the two blacks did. ...which is ANOTHER mystery.

No mystery. You have a lightbulb installed but the switch is off.

> I thought there was no load in the circuit, but the hard-wired smoke alarm may have been
> in the loop. Does this change anything?

Of course. It completely explains "why two whites would conduct [sic] 120 volts."
 
  #9  
Old 03-14-06, 06:14 PM
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OK, now I'm starting to learn something: so if I complete the circuit with an electrical device "downstream," then touching two blacks (or two whites) in a different outlet box COULD show a reading with my lamp tester?

Maybe I was thinking of the DC model in my head instead of AC (I'm still learning some of the basics).

By the way, thank you to eveyone who has replied to my posts.
 
  #10  
Old 03-14-06, 07:05 PM
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> if I complete the circuit with an electrical device "downstream," then touching two blacks
> (or two whites) in a different outlet box COULD show a reading with my lamp tester?

Yes. But the explanation is no mystery.
It is quite predictable when and where there is voltage and/or current.

The thing is that your lamp tester uses trivial current.
If you stick one end on a black wire and hold the other end in a sweaty hand, can you even feel the current? I can't.

So your tester indicates the presence of voltage.
But it does not tell you hold much current is available. A wiggy is better as it screens out truly phantom voltages.

The best indication comes from knowing what to expect and if the reading is consistent with the expectation. Then take readings on an open circuit and under load.

Actual mysteries are explained by loose wires, shorts, blown bulbs, failed devices, etc.
In the end, there is nothing strange about it.


> Maybe I was thinking of the DC model in my head instead of AC

You would see exactly the same situation with 120VDC (except that the smoke detector might not draw any current depending on its power conversion). So let's say that it was replaced by a little lightbulb of equal wattage.

There is nothing special about AC that explains this simple circuit that is any different from DC.
 
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