ECN Forum Forums General Topics of the Trade General Discussion Area Multiwire (Edison) circuits and GFCI

I reckon it wouldn't hurt to mention some history of this thing on my behalf.

Once I discovered the spaghetti-bowl-in-a-handy-box fiasco, I went to shut off the breaker to the clothes washer. I then checked the voltage with my trusty digital VOM- 15 volts... HMMMM... my thoughts were a possible failing breaker or (perhaps) a minor carbon track somewhere within it, or something. Upon further investigation I found a second outlet not too far away and it appeared to be wired to this same circuit. Checked the voltage- 120. It was only then that I realized the circuit was Edisoned. Found the other breaker three-up from the washer circuit, on the opposite leg, shut it off, checked the voltage- zero volts; a little bit safer to work on.

My thinking about this was that, if this "back EMF" from the opposite leg was somehow "seen" by the GFCI outlet it would cause nuisance tripping but for some reason it would work fine at the end of the circuit run (perhaps) because nothing was downstream of it, somehow upsetting the circuit balance (in retrospect, it appears that my logic has some holes in it. Even so, theory and practice are oftentimes different worlds).

Even if the GFCI outlets do work fine at the beginning of the circuit and using the feedthroughs were no problem, this (in my opinion) should never be done as the integrity of the neutral grounded conductor should be totally device-independent on multiwire circuits. Pigtails prevails... Just my opinion...


[This message has been edited by Sir Arcsalot (edited 03-15-2004).]

[This message has been edited by Sir Arcsalot (edited 03-15-2004).]

This reading was nothing to worry about, a digital VOM reads induction from the other circuit, try the same measurement with analog meter.

I run many multiwire branch circuits and as long as you follow the rules that apply to them they work great, how many service entrance neutrals do you have?

GFCIs do work down line from a multiwire branch circuit, not some times, every time.

Compare a GFCI fed from a multiwire branch circuit to a GFCI fed from a 2 wire branch circuit.

Once you get back to the panel it is the same thing, a common neutral.

One thing you can not do is protect outlets down line on a multiwire branch circuit with a GFCI outlet.

This is what electure and Electric Eagle where saying.


[This message has been edited by iwire (edited 03-16-2004).]

Sometime last evening I thought about induced voltage being the likely source. Yesterday it seemed as though my brain spent a few hours in a paint shaker.

Thanks a great big bunch to all of you for your insight and expert advice on this matter; I think my light bulb is fully socketed now.

I have another, semi-unrelated question that I can't find the info for on this board: how do you box in the quotes with those lines? I don't know how to make the lines appear, though it's probably very simple.

[This message has been edited by Sir Arcsalot (edited 03-16-2004).]

When you click on "reply" you get the screen I am writing in now. To my left is a link labeled "*UBB Code is ON". Click on this link to see the rules.

Earl

You can also click on edit for any post that has the effect that you are trying to duplicate and you will see the UBB code. You can't edit any posts except your own, but you can see the code.
Don