Two GFCIs, one box, two circuits

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  #1  
Old 08-04-07, 11:06 PM
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Two GFCIs, one box, two circuits

I'm replacing two GFCIs in my laundry room. The GFCIs are in a double-gang box.

The left-side GFCI and right-side GFCIs are controlled by separate 20 amp breakers. So when I opened the box, I expected to find two unrelated sets of wiring.

Instead, what I found was wiring which I didn't fully understand. After some research, I believe that this may be a multi-circuit.

It's is trivial for me to simply hook up things the way they were before with the new GFCIs. (I've marked all the wires so I know exactly where they go.)

But I want to make sure (before I re-hook them up the way they were before) that the wiring is correct and makes sense.


Here is how it was wired:

1) There are three Romex cables coming into the box. (Note that the LOAD side was not used on either GFCI.)

2) The left-side GFCI has one hot black wire attached to its LINE side, and two neutrals attached to its LINE side: one neutral nutted with the neutrals from the incoming cables, and the other neutral attached to the LINE side of the right-side GFCI.

3) The right-side GFCI has two hot wires attached to its LINE side, a red one and a black one. The only neutral attached to the right-side GFCI is the wire which has its other side attached to the left-side GFCI.


I uploaded a picture which might make my description more clear (note that the blue taped wires represent those which came out of the LINE side of the left-hand GFCI.):


http://www.headworld.net/pictures/gfci.jpg


Is this the correct wiring? As I mentioned earlier, both sides are controlled by different breakers.

Thank you!
 
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  #2  
Old 08-05-07, 06:51 AM
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What you neglected to tell us is very important.

What else is on both circuits?

Tell us what wires exist in those 3 NM cables and how those wires are connected. Account for each and every wire and all three cables.

Tell us about the circuit breakers serving this circuit. Are there two separate breakers? One 240 volt breaker? If separate breakers, are they on different legs of the incoming 240 volts?

It sounds like you have a multi-wire circuit feeding this location, which then feeds other locations as two separate circuits. However, without the proper information about how the wires are hooked up we cannot be certain.
 
  #3  
Old 08-05-07, 12:05 PM
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OK, I've done the research to answer your questions as best I can. (Sorry that I don't know all the terminology. )


THE BREAKERS:

The breakers are 20 amp half-height breakers which are on the top half and bottom half of two adjoining slots. They are not attached together (meaning that they can be individually turned on and off.) In between them is a circuit which supplies an appliance: two 20 amp breakers tied together.

I put up a picture of the breakers, with yellow arrows pointing to the two breakers in question (11 Top and 9 Bottom.) They're the ones turned off in the picture.


http://www.headworld.net/pictures/breaker.jpg


WHAT DO THE CIRCUITS POWER?

As far as I can tell, the only other things on these circuits are 3 other receptacles in the laundry room and 2 receptacles in adjoining bathrooms. No lights and/or fans appear to be on this circuit.

Even with the two GFCIs totally unhooked (and all the wires formerly attached to them left free) all of the other receptacles on the circuit work.


WHERE DO THE WIRES GO IN THE BOX?

First, I was wrong in my original assessment... there are actually 4 NM cables coming into the box. (There are a lot of wires and not a lot of light so it was hard to see what is going on.)

Three of the cables are 12-2, one of them is 12-3.

The hots of the 12-3 cable are hooked up as follows:

* RED to the right-side GFCI LINE
* BLACK to the left-side GFCI LINE

All 4 incoming neutrals are nutted together, and a pigtail is run to the neutral LINE of the left-hand GFCI.

The other 3 incoming black hots (from the three 12-2 cables) are nutted together, and a pigtail is run to the hot LINE of the right-side GFCI.

All 4 grounds are nutted together and pigtailed to both GFCIs.

A neutral wire connects the LINE side of the two GFCIs.


FROM THE PERSPECTIVE OF THE GFCIs:

Here's another way to envision the wiring, from the perspective of the GFCIs.


LEFT-SIDE GFCI:

* HOT LINE: One wire, the black hot from the 12-3 cable.

* NEUTRAL LINE: Two wires. 1) A pigtail coming from the nut containing the 4 incoming white wires from the four incoming cables. 2) A white wire attached to the LINE of the right-side GFCI.

* LOAD: Not used.

* GROUND: Nutted with all other grounds in the box.


RIGHT-SIDE GFCI:

* HOT LINE: Two wires. 1) A red wire coming from the 12-3 cable. 2) A black pigtail coming from the nut containing the 3 incoming black wires from the three 12-2 cables.

* NEUTRAL LINE: One wire, connected to the LINE side of the left-side GFCI.

* LOAD: Not used;

* GROUND: Nutted with all other grounds in the box.


Thanks for your help, please let me know if I can provide any other information.
 
  #4  
Old 08-05-07, 01:12 PM
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You have a multi-wire circuit. It does not meet current code due to the receptacle in the laundry and the bathroom receptacles. However, there is nothing unsafe about the wiring itself.

Having said all that, if you connect the wires exactly as they were you will have the same thing you started with.
 
  #5  
Old 08-05-07, 03:05 PM
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So in your opinion (given the older code it conforms to), the actual wiring itself is correct and I should simply hook it up as it was and it's OK?

In reading about multiwire circuits I read about neutrals overheating due to improper wiring, in particular if the two circuits are not on different legs.

Is this something I should be concerned about in this case, and how does one determine which leg each circuit is on?

Thanks!
 
  #6  
Old 08-05-07, 03:25 PM
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You already determined that the hot wires are on separate legs. You looked at the circuit breaker.

To confirm this, measure the voltage between the hot wires. You will get 240 volts.
 
  #7  
Old 08-05-07, 04:43 PM
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I measured between the two hot wires coming out of the 12-3 cable (the red one and the black one) and it reads 240 volts.

Are those the two hot wires I should be measuring the voltage between?

(Measuring between the red hot and the pigtail black, I get 120 volts.)
 
  #8  
Old 08-05-07, 06:23 PM
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Yes, between the black and red should be 240v.
 
  #9  
Old 08-05-07, 06:32 PM
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Thanks. I replaced them, rewiring as before and everything appears to work.

I redid the pigtails because whomever originally installed them used #14 wire to pigtail (even though all of the incoming wires are #12.)

Thanks for all the help!
 
  #10  
Old 08-06-07, 10:45 AM
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The only concern is that the neutral of one GFCI is fed through the other, which you shouldn't do on a multiwire circuit. You need to run separate neutral pigtails from each receptical to the neutral bundle in there.
 
  #11  
Old 08-06-07, 11:48 AM
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Is see. Is this required? What condition is this designed to prevent?

In reading, it seems like this might be a best practice in case the two circuits end up on the same leg and a downstream receptacle could end up being fed 240 volts?

In this case, the two circuits are on different legs so I thought there was no problem.

I could definitely change the wiring again, but it would be a huge pain (it's in a very inaccessible location) and so if it's not truly necessary, I'd rather keep it as it is currently wired.

Could you help me understand the issues here? Thanks!
 
  #12  
Old 08-06-07, 11:58 AM
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Question

I'm just a novice and don't know to much (lol) I drew a little lateral diagram as we do in the Hvac industry and it appears to me that the three other 12/2 loads are getting "tapped" power of the right hand side gfi. If there is a ground fault in any of these three other loads (whatever they are) wouldn't that trip the rhs gfi, even though the three loads tapped of this gfi aren't hooked up in a Line Load fashion?? Perhaps I'm not seeing it correctly though. Thanx Is it Ok to butt in like this?
 
  #13  
Old 08-06-07, 11:59 AM
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I do not see a problem with this setup. The neutrals are pigtailed to the first GFCI.

I see this setup the same as a duplex receptacle with a broken hot side tab from both halves of the incoming circuit.

The code, by the way, is trying to prevent the case where the neutral has failed and items plugged in further down the circuit end up fed with more or less than 120 volts.
 
  #14  
Old 08-06-07, 12:02 PM
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sidecutter, nothing is being fed from either GFCI. There is nothing connected to the LOAD side of either GFCI. All connections are to the LINE side of the GFCIs.
 
  #15  
Old 08-06-07, 12:32 PM
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Smile

Ray thanx for immediately adressing my question. I do understand that nothing is being fed from the "load side" of either gfi. Are these other loads 12/2's not connected to (have a connection with) the hot and grounded conductor of the rhs Gfi?? Would this not put these loads in parrallel with the "line side connections of the rhs gfi"?? I suppose it's possible to do this!! If so would not a ground fault in any one of these three loads trip the Gfi? If I don't get it by your next response I'll go back to my reading (lol) thanx
 
  #16  
Old 08-06-07, 12:48 PM
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Nothing on the LINE side of a GFCI will trip it.
 
  #17  
Old 08-06-07, 10:06 PM
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Smile

Mused over your reply for about an hour and had a mini "awakening". Alles klar (all clear) thanx
 
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