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US, Georgia I am adding some new ciruits to add some additional outlets. The closest place is to run a wire to the main panel box.

My question is, can I connect more than one wire to a breaker and still meet code or do I need to get a new breaker. Both the wires and plugs are the same rating as the breaker - 15 amp.

Making the assumption that only one wire can be under each screw in the breaker, can I make a junction in the panel box? IE, one wire to breaker, but two wires to a wire nut connecting them together, or does the junction need to be in a separate box?

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This page includes pictures of breakers that take 2 wires: structuretech1.com/2010/01/… –  Jay Bazuzi Jul 16 '12 at 5:39
    
For future googlefu, you should know that in the 2 wires->nut->1 wire scenario, the nut + wire is known as a "pigtail", and the whole scenario would be described as "pigtailing" the wires. –  Jeremy W. Sherman Jul 16 '12 at 16:37
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3 Answers

up vote 8 down vote accepted

There should only be one wire per screw terminal. One of my wiring books says that some local codes allow splices inside a service panel, and some don't, so you should check with your local authority to make sure it's OK in your area.

However, regular circuit breakers are only a few dollars, so even if it's allowed in your area, my advice would be to just install the extra breakers for the new circuits.

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Recent Code specifies AFCI breakers for almost everywhere. Those breakers are $35 a pop, not $3.50 a pop, which makes using an existing circuit much more appealing. –  Jeremy W. Sherman Jul 16 '12 at 16:38
    
Also: If the authority having jurisdiction says no to in–panel-box splices, you can identify the cable leaving the panel box and make the splice in a junction box near the panel instead of in the panel. But you really should map out your circuits first to make sure you're not going to give yourself brownouts on that circuit. –  Jeremy W. Sherman Jul 16 '12 at 16:39
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Double Taps

With most devices you can only have one wire per screw terminal, however, some breakers do support multiple wires under terminals. If the device allows multiple taps, it must be listed for the purpose.

NEC 2008
110.14 Electrical Connections.
(A) Terminals. Connection of conductors to terminal parts shall ensure a thoroughly good connection without damaging the conductors and shall be made by means of pressure connectors (including set-screw type), solder lugs, or splices to flexible leads. Connection by means of wire-binding screws or studs and nuts that have upturned lugs or the equivalent shall be permitted for 10 AWG or smaller conductors.
Terminals for more than one conductor and terminals used to connect aluminum shall be so identified.

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Taps, Splices, and Feed Throughs

Feed throughs, taps, and splices are allowed, but only if they do not over fill the enclosure.

NEC 2008
312.8 Enclosures for Switches or Overcurrent Devices. Enclosures for switches or overcurrent devices shall not be used as junction boxes, auxiliary gutters, or raceways for conductors feeding through or tapping off to other switches or overcurrent devices, unless adequate space for this purpose is provided. The conductors shall not fill the wiring space at any cross section to more than 40 percent of the cross-sectional area of the space, and the conductors, splices, and taps shall not fill the wiring space at any cross section to more than 75 percent of the cross-sectional area of that space.

Tandem Breakers

If you have no room for a new breaker in the panel, consider a Tandem Breaker. You'll have to check whether or not your panel supports them, but in some cases a tandem breaker can save you from having to install a new panel or a sub-panel.

Code Changes

In the 2008 version of the National Electrical Code (NEC), section 210.12 has been updated to require Arc-Fault Circuit-Interrupter (AFCI) protection in many areas of the home.

NEC 2008
210.12 Arc-Fault Circuit-Interrupter Protection.
(B) Dwelling Units. All 120-volt, single phase, 15- and 20-ampere branch circuits supplying outlets installed in dwelling unit family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets, hallways, or similar rooms or areas shall be protected by a listed arc-fault circuit interrupter, combination-type, installed to provide protection of the branch circuit.

Depending on the changes you're making to the wiring, the inspector may require you to update the breaker for this or all branch circuits feeding these areas. This decision will be completely up to the Authority Having Jurisdiction (AHJ), since it's a judgment call on whether or not you're making a large enough change to warrant the extra work.

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If you want to connect two load wires to a breaker, you must use a breaker that is "labeled and listed" for two wires.

Otherwise a wirenut connecting two circuits to a pigtail should be ok, as it is not a "circuit passing through" which would fall under the prohibited junction box usage.

A Tandem Breaker is of course the best solution, as long as you comply with the number of breakers for which the panelboard was designed, rated, and listed, since you won't have to worry about how much amperage you can take from the existing circuit.

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