multiwire branch circuit problems

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  #1  
Old 02-20-10, 10:40 PM
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multiwire branch circuit problems

Our house is new, built in 06. A month ago our bathroom circuit went out. Apparently it's on a multiwire branch with the laundry washer. The only GFI on the circuit is in the bathroom.

An electrician disconnected and reconnected the laundry outlet and now the bathroom outlets are working; apparently that made the GFI happy again. He didn't know why this helped.

The other weird thing is that using the washer or bathroom outlet causes our touch lamp in the adjacent bedroom to come on; we have a number of touch lamps throughout the house, only the bedroom is affected. Completely different circuit, and the breaker for the bedroom is on the opposite side of the panel.

The electrician was stumped, but thought this could be a fire hazard - insulation compromised somewhere.

Could these problems be caused by something less severe? Would rather not have to open the walls and look for a bad wire casing.

Thanks in advance.

 
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  #2  
Old 02-20-10, 11:47 PM
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There one thing that kinda bother me but I do not know if your state did allow MWBC for bathroom and laundry room circuit like that myself I will never run like that at all { state of Wisconsin do not allow MWBC between bathroom and laundry room at all they have to be it own circuits no MWBC at all }

Second thing is your house pretty dry ? if so it can get pretty senstive.

Now the other issue if your electrician can not find the cuprit he should pull out the megger tester to verify the cable insluating materal is still good that what I will do next step due I am used with French codes we have to run the megger test all the time.

The megger testing mean it will induce higher voltage but very limited current it will tell if your insluating is in safe zone or not and some case if you can read the megger right you can able pinpoint where it is.

I know not very many resdentail electrician use this tool but industrail and commercal electrician are famauir with it.

The other thing with that new a house they should have oringal electrician to come out and see what the issue there.

Merci,Marc
 
  #3  
Old 02-20-10, 11:51 PM
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You need to be scientific about these things.

As to the outlets in the bathroom not working, it is too late now, but each individual wire could have been tested for continuity through to the breaker panel. Many different ways to test the wiring. There may have been a loose connection along the way.

Then as for the touch lamp, again be scientific. Try moving that lamp into another room and the lamp in the other room into the bedroom. See if the same problem happens. Or if perhaps the lamp which was moved now turns on in the other room.

Then learn how the touch switch works for that specific light.
The following page says these can work several ways...
(Call the lamp manufacturer if you can and ask how they work.)
HowStuffWorks "How do touch-sensitive lamps work?"

The above says skin temperature, resistance, and radio reception, or capacitance.

Then you could try measuring the voltage at that outlet when the washing machine turns on the light. See if the voltage is dropping.

Or if you have a computer UPS, connect that to the lamp and turn of the UPS without it being plugged in. This would power the light without it being connected to the wall outlet. Then if the light came on, it would be something "in the air" like EMI (ElectroMagnetic interference)...
Electromagnetic interference - Wikipedia, the free encyclopedia

Or leave the lamp in the room, but run a long extension cord from an outlet in another room. Try moving the lamp around in the bedroom while powered by the long extension cord.

Or plug a long extension cord into the bedroom outlet where it is currently plugged in, then move the lamp into another room. See what happens.

And you could make a "Faraday Cage" around the lamp with aluminum foil and see if that makes the problem go away.

Faraday Cage...
Faraday cage - Wikipedia, the free encyclopedia

Which of the above you would experiment with would of course depend on how the touch switch operates.

Once you find the problem, then you may be able to find a solution. I've had to modify some products "new out of the box" because they were not designed right. I'm doing this a LOT more lately.

Perhaps someone could start a new business... People buy something new, then take it this business to have it fixed so they could then use it!
 
  #4  
Old 02-21-10, 11:48 AM
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Bill190 - I've checked non-affected lamps in the bedroom and moved the touch lamp to multiple rooms and outlets... regardless of the touch lamp, it only mysteriously comes on in the bedroom - and only when the bathroom and laundry outlets are used.

I'm not concerned with a defective lamp - my concern of course is the electrical problem.
 
  #5  
Old 02-21-10, 12:23 PM
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nuetral issue

I am thinking the bed room neutral is somehow tied with the MWBC, ( which it shouldn't be ), the bedroom should be on it's own ARC fault breaker, and it probably picking up on the neutral side ( the touch lamps ), or you got a current leak ( like a small nick in the wiring ) via the neutral.
 
  #6  
Old 02-21-10, 03:20 PM
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Originally Posted by mikerios View Post
I am thinking the bed room neutral is somehow tied with the MWBC, ( which it shouldn't be ), the bedroom should be on it's own ARC fault breaker, and it probably picking up on the neutral side ( the touch lamps ), or you got a current leak ( like a small nick in the wiring ) via the neutral.
How serious are either of these scenarios? What's the potential fire hazard threat?
 
  #7  
Old 02-21-10, 03:50 PM
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My bedroom receptacles are on a multi wire branch circuit (pre AFCI requirement) and I have two of the "touch" lamps. One of them will mysteriously come on due to some action elsewhere in the house but the other seems immune. There is nothing inherently wrong or unsafe about MWBCs so if I were you I'd either replace the lamp, replace the module inside the lamp or just live with it.

It is not a hazard, just annoying.
 
  #8  
Old 02-21-10, 11:09 PM
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Originally Posted by furd View Post
My bedroom receptacles are on a multi wire branch circuit (pre AFCI requirement) and I have two of the "touch" lamps. One of them will mysteriously come on due to some action elsewhere in the house but the other seems immune. There is nothing inherently wrong or unsafe about MWBCs so if I were you I'd either replace the lamp, replace the module inside the lamp or just live with it.

It is not a hazard, just annoying.
I don't want to get too off issue with the lamp; I don't really care that it comes on per se... only that it might be a sign of something more severe considering the laundry knocked out our bathroom circuit. Just looking for theories that might explain how all of this is connected.
 
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