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Can I join two or more branches within a panel to a single circuit breaker housed in that panel?

Can I do this for multiple circuits?

What limitations, if any, do I need to observe?

Which section of the code covers this situation (so I can point the inspector to it if there are any questions)?

Background

I am the homeowner and we are in the process of converting a 1960's barn into finished space. The governing building codes are defined here. A building permit has been pulled and all work will be inspected. I am doing the electrical work myself.

About seven years ago, we hired a licensed electrician to install a new 100A sub-panel in the barn (connected to 200A main panel in the residence). This is a Siemens "2020" panel. Minimal circuits were installed to support livestock (cow, goats, sheep) and related storage in the barn. These previous circuits and all old fixtures are being removed as part of this project.

At this point, we are converting the barn for use as a 7BBL (propane-fired) nano-brewery and tasting room. I planned the the electrical for 16 circuits, with four left available for the plumber (HVAC). The plumber changed his plan and now needs six slots in the panel, so I need to reduce my number of circuits from 16 to 14.

The plumber told me "this is not a problem, you just need a couple of tandem breakers." In researching my panel, it appears that my panel does not support tandem (QT) type breakers.

If it is allowed, my preferred plan would be to pick appropriate branches to put on the same breaker and make this junction within the panel housing the breakers. This would allow me to "re-balance" the circuits in the future if needed simply by making changes within the panel.

If necessary, I can create junction boxes outside of the panel. Are there other alternatives?

The building inspector is one of my neighbors and I can ask him what he would prefer to see. However, I would rather just do it the right way without having to ask him too many questions.

What is the "right" (as opposed to "DIY") thing to do here?

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    Why not just install a small 30A or 50A subpanel and move some circuits to it? If this is an unfinished space this should be pretty straightforward. – Johnny Nov 15 '16 at 17:20
  • @Johnny Thanks for the suggestion. This is certainly an alternative. – Rob Nov 15 '16 at 17:24
  • You can splice circuits inside the panel. You are still limited on the total number of outlets on each breaker. A 15 amp circuit is usually limited to 8 (80% of 15 amps 180va for each yoke). A 20 amp circuit (80% of 20 amps / 180va). Some states are very strict on the 80% max load some will allow 100% of the breaker value. I have seen post on this site that said there was no limit maybe in there state? The NEC uses 180 va or 1.5 amps per yoke ( 1,2,3 outlets I have not seen a 4 outlet single yoke). The NEC also limits the load to 80%. So that's where I come up with the values above. – Ed Beal Nov 15 '16 at 18:46
  • @EdBeal Can you confirm that by "splice" you mean that I can connect three or more wires (e.g., using a nut)? In other words, not just two wires to effectively make a longer wire. Thanks! – Rob Nov 15 '16 at 18:55
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    It sounds like this might be a commercial space now: "nano-brewery and tasting room". So residential codes might not apply. – Johnny Nov 15 '16 at 20:15
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Yes, you can have splices in the service panel. However, you cannot combine circuits that are required to be separate (if any). You also cannot combine circuits, such that you're overloading the circuit.

A breaker terminal (or any terminal really) can only have one conductor terminated, unless the terminal is listed and labeled otherwise. Some breakers are listed and labeled for two (2) copper conductors, but not all are. If the breakers you're using are not, you'll have to splice a pigtail to the breaker terminal (though based on your question, it sounds like that's what you're planning anyway).

Fill rules apply, but it would take quite a bit to overfill a panel.

  • Even in cases where breakers are designed for two conductors? – isherwood Nov 15 '16 at 22:25
  • @Tyson I've edited my answer. – Tester101 Nov 15 '16 at 23:18
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    @Tester101 Mike Holt's explanation of the fill rule is a pretty good one: "If you have to squash the wiring down to get the cover to fit, you are over 75% fill" – Mister Tea Nov 15 '16 at 23:39

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