Two Single-Pole vs Double-Pole Breaker/GFCI

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  #1  
Old 08-28-05, 06:07 PM
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Need Help Interpreting Inspector's Comments

I am installing 10/3 w/grnd UF cable underground from a sub-panel in my basement to an outbuilding. The town building inspector, when approving my application for a permit, attaches a note saying “with existing subpanel (4-wire) use a subpanel w/4-wire in detached structure”. I’ve two questions someone here can probably help me answer. Any insight would be appreciated.
(1) Would I be correct in assuming “4-wire” means two hot wires, a neutral and a bare grounding wire?
(2) Why do I need a subpanel on each end of the underground cable? I was planning on a 15 amp double-pole breaker in the existing subpanel to protect the two 120 volt circuits in the outbuilding and the underground cable to get them there. What do I gain with another subpanel and more breakers?
 
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  #2  
Old 08-28-05, 06:17 PM
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(1) Yes.
(2) If this is the only electrical cable to the outbuilding, then you don't need the subpanel. The inspector probably assumed that you were going to install a subpanel because you used 10-gauge wire. Unless the distance is over 200 feet, most people would have used 12/3 or even 14/3 instead of 10/3. When you applied for your permit, did you submit a plan that clearly showed one multiwire circuit and no subpanel?

The cable needs to be buried at least 24" deep. And you'll need two switches to serve as a disconnect. And you'll need two GFCIs to provide ground-fault protection. Without the subpanel, you won't need a grounding rod.

Note the restriction I mentioned above about this being the only electrical supply to the building. You aren't allowed more than one.
 
  #3  
Old 08-29-05, 02:35 AM
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fingerpost,

The only issue that might have caused them to make the statement was if you has said this quote as you did in the post.

two 120 volt circuits in the outbuilding and the underground cable to get them there. What do I gain with another subpanel and more breakers?
You did not state (1) 240V circuit or (1) 120V circuit....you stated you wanted (2) 120V circuits....so you are given the impression you are doing a multi-circuit in the detached building and this would require a sub-panel, ground rod and so on.

John is refering to Art 250-32 (ex) which allows the EGC within the cable itself thus not having to have its own GEC at the detached building but this is not going to be possible if you are doing exactly as you describe in the statement you posted.

Now if you just refered to them as (2) because phycially their are two in the cable then you are fine.....as long as it is (1) ONE branch circuit for use in the detached building.
 

Last edited by ElectricalMan; 08-29-05 at 06:59 PM. Reason: Cleaned up the ECG and GEC Typos...lol
  #4  
Old 08-29-05, 08:16 AM
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Although he said "two 120 volt circuits in the outbuilding", he didn't mean it.

Because he said he was running this from a "15 amp double-pole breaker", and because he said that that he was "installing 10/3 w/grnd UF cable", I translated his "two 120 volt circuits" to "one 15-amp multiwire circuit".

This latter terminology is what you should say in your plans instead of the former term if you want them to approve this without the subpanel.

BTW, the grounding wire in the 10/3 is an EGC, not a GEC. When only one circuit and no subpanel is used in an outbuilding, no GEC is required.
 
  #5  
Old 08-29-05, 09:48 AM
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Don't forget to install a disconnecting means

in or on the outbuilding.

NEC 2005 Article 225.39(B) Two-Circuit Installation. For installations consisting of not more than two-2 wire branch circuits, the feeder or branch-circuit disconnecting means shall have a rating of not less than 30 amperes.
 
  #6  
Old 08-29-05, 06:08 PM
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Thank you all for your comments.

Despite my incorrect terminology I believe you have given me the information I need. John’s interpretation of my statements was indeed what I was trying to say. The building inspector was not supplied enough detail and made an assumption. I’ll clarify that with him. Thanks.
 
  #7  
Old 08-29-05, 06:57 PM
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ok John...can't a brother have a few typo's...lol.......and my post was really just to clarify his (2) 120V circuit comments for others...
 
  #8  
Old 08-29-05, 11:54 PM
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Originally Posted by thinman
in or on the outbuilding.

NEC 2005 Article 225.39(B) Two-Circuit Installation. For installations consisting of not more than two-2 wire branch circuits, the feeder or branch-circuit disconnecting means shall have a rating of not less than 30 amperes.


A multiwire circuit is not two 2-wire circuits. Would section 225.39(B) apply to a multiwire circuit?

Section 225.30 says a multiwire circuit shall be considered a single branch circuit.

Section 225.39(A) says the loads of a single branch circuit shall have disconnecting means with a rating of not less than 15 amperes.
 
  #9  
Old 08-30-05, 10:58 AM
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Originally Posted by Juhl
A multiwire circuit is not two 2-wire circuits. Would section 225.39(B) apply to a multiwire circuit?

Section 225.30 says a multiwire circuit shall be considered a single branch circuit.

Section 225.39(A) says the loads of a single branch circuit shall have disconnecting means with a rating of not less than 15 amperes.
Oops! My bad!!
 
  #10  
Old 10-06-05, 10:46 AM
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Two Single-Pole vs Double-Pole Breaker/GFCI

In a previous post, I asked for, and was given, help regarding the installation of 10/3 w/grnd UF cable underground from a subpanel in my basement to an outbuilding. I learned that what I was installing was called ‘a single multiwire circuit’.

In his reply, John Nelson wrote: “The cable needs to be buried at least 24" deep. And you'll need two switches to serve as a disconnect. And you'll need two GFCIs to provide ground-fault protection.”

I now have the cable buried (24” deep and over 200 feet long) and now I have another question concerning connecting into the subpanel. Can I use 2 single-pole 15amp breakers/GFCI units, which I was able to find at Home Depot, or must I use a double-pole breaker/GFCI unit, which I haven’t yet found? If 2 single-pole breakers/GFCI units are okay, how do I connect the single, shared white neutral with these two units? These breaker/GFCI units have an attached pigtail which is supposed to go to the neutral busbar.
 
  #11  
Old 10-06-05, 10:56 AM
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Two single-pole GFCI breakers (or receptacles) cannot be used to protect a multiwire circuit whenever the neutral is shared downstream. You would need the more expensive double-pole GFCI breaker.

However, you can avoid this by simply splitting the neutral once you get to the outbuilding (running two 14/2 cables off, one in each direction). Then two ordinary GFCI receptacles can provide the required protection, one on each 14/2.
 
  #12  
Old 10-06-05, 01:02 PM
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John,

So what you are saying is that GFCI protection is required only for receptacles? I’ll take your suggestion and put the GFCI’s in the outbuilding. Thanks so very much for your help.
 
  #13  
Old 10-06-05, 01:34 PM
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Correct. GFCI protection is required only for 120-volt receptacles.
 
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