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Thread: What are rules for double-tapping breakers

  1. #1
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    What are rules for double-tapping breakers

    I am a home inspector and often see double tapped breakers in panels. My working knowledge of this is the following:

    1. Square D is the only manufacturer that designs breakers to support 2 wire connections.
    2. The rated load from both circuits cannot exceed 80% of the breaker rating.
    3. Double-tapping increases the risk of nuisance trips (mainly due to violation of Item 2).
    4. Double-tapping is generally looked upon as a deficiency.

    I hope to get some clarification because occassionally an argument develops when I call this a defect. What other things should I be aware of?

    Thanks in advance for anyones help.

    Tony
    Tony Shupenko, PE

  2. #2
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    Re: What are rules for double-tapping breakers

    Tony, 1 through 4 are all false.

    #1 Cuttler Hammer also makes breakers identified for use with two conductors.

    #2 How do you know the loads are continuous. A breaker can be loaded to 100% for 179 min 59 sec.

    #3 Just plain false

    #4 Just plain false. In laying out a circuit it may be advantageous to shorten the overall conductor length by leaving in two directions from the panel, and if the breakers are listed for two conductors, why waste a junction box?

    Roger

    [ September 26, 2005, 02:23 PM: Message edited by: roger ]
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  3. #3
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    Re: What are rules for double-tapping breakers

    1. I would not make such a blatant statement. Cutler-Hammer CH 15-30A breakers are listed for (2) #14-10 conductors.
    2. All breakers need to be sized to carry 100% of any non-continuous load plus 125% of any continuous load.
    3. Any breaker will experience nusiance trips if rule 2 is not followed. Double tapping is no more of a culprit than running a single conductor to a junction box and then making the "double tapping".
    4. Why?? When used correctly it can eliminate a junction box/point.
    Just because you can, doesn't mean you should.

  4. #4
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    Re: What are rules for double-tapping breakers

    Originally posted by tonype: I hope to get some clarification because occasionally an argument develops when I call this a defect. What other things should I be aware of?
    I commend you for being safety-conscious. It is a good question, and it does not have an easy answer. In fact, the only NEC article that I could find to back up your "calling this a defect" is going to come across (to your clients) as a bit "wishy-washy." The article is 110.3(B). It says,
    Listed or labeled equipment shall be installed and used in accordance with any instructions in the listing or labeling.
    If a breaker has two wires connected to it, and if the breaker was not listed for use with two wires, then it is a "defect," in the language of your profession. In our language, we would call it an "NEC violation."

    On the other hand, if you see a breaker that is rated for two wires, and that has two wires, it will be tough for you (and even tough for an electrician) to tell if the load exceeds the rating of the breaker. You would have to have a list of everything that is connected to each wire, and have either the nameplate rating of each load or some other basis for determining the load. What Roger was referring to in his response to your Question #2 was that it is OK to load a 20 amp breaker to 20 amps, if the loads are not going to run "continuously." That term is defined as longer than 3 hours. So if you don't know the load, in detail, you can't reasonably call this a "defect."

    Perhaps the best you can do is to cite the double-wire condition as something that you recommend be investigated by an electrician, since it is beyond your role to determine what is, and what is not, an NEC violation.

    By the way, in our language, the words "tap" and "tapping" do not apply to the practice you are describing. I have heard this called "double-lugging a breaker," but not "double-tapping a breaker."
    Charles E. Beck, P.E., Seattle
    Comments based on 2014 NEC unless otherwise noted.

  5. #5
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    Re: What are rules for double-tapping breakers

    Roger, Jim and Charlie:

    Thanks for the quick reply. I get more useful stuff from you guys all the time.

    I guess it shows that what we are "taught" - some though word or mouth and some from seminars - is not necessarily complete/accurate. My conclusion is that this condition may or not be a problem - I will just flag it in the future and tell the client to request a licensed electrical contractor to review.

    Again, thanks

    Tony
    Tony Shupenko, PE

  6. #6
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    Re: What are rules for double-tapping breakers

    Let me add that there have been times when I used a wire nut on two circuits to one conductor to go under the breaker. As well, I used a wire nut on the equipment grounding conductor for the grounding bar in a panel. This was done in a panel upgrade.
    Mike Whitt
    God answers Knee-Mail.

  7. #7
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    Re: What are rules for double-tapping breakers

    Some times there is no choice and it is legal to make a joint up in a panel(2 circuits on one breaker.Just watch which you chose to do this on :o
    Like I said sometimes there depending on circumstances this may be the only recourse you have.If there was all the time in the world well then there is no excuse.But there are always dealines , Number crunching,la da da da da
    Would I if time permitted encourage this nope !!!!41 circuits in a 40/40 panel and in a pinch I have done this .But I assure you the guy that roughed the place in knew that he had better count his circuits :mad: in the future or he could work for DTR electric

  8. #8
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    Re: What are rules for double-tapping breakers

    Before my panel was loaded to the gills, every circuit I ran was on it's own breaker whether it need to be or not. Now that it's loaded (as well as the sub) a few circuits have been combined. This isn't a design flaw nor is it dangerous.

    There is an assumption that 2 wires on one breaker, or a splice inside a panel, indicates 2 loaded circuits have been combined. It would require further investigation to find out if that's the case or not.

  9. #9
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    Re: What are rules for double-tapping breakers

    Originally posted by allenwayne:
    Some times there is no choice and it is legal to make a joint up in a panel(2 circuits on one breaker.Just watch which you chose to do this on :o
    Allen, why is it shoddy to make a splice in a panel? It's no different than making a splice in a junction box.

  10. #10
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    Re: What are rules for double-tapping breakers

    I would be more concerned with double lugging of the neutrals and combining of neutral and grounds on the neutral bar.
    Tim
    Master Electrician
    New England
    Yesterday's Technology at Tomorrow's Prices

    Answers based on 2011 NEC

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