I have built a detached garage which will have a 125A subpanel. (125A panel because it will double as a work shop with A/C and heat and power equipment). Power will brought in from the house load meter panel which only has 12 spaces which are all taken. In fact, several spaces are occupied by tandem breakers to carrying 220V circuits requiring the second hot leg to be carried by another tandem breaker with a space in between in order to pick up the other side of the bus. (I think this is illegal or should be. This is the way the panel was wired when we purchased it).

With the second panel installed adjacent to the meter base, I plan to get rid of all tandem breakers (which I do not like anyway) and move several breakers to the new panel which has 24 spaces, freeing up spaces in the meter base panel where I will install the 125A breaker to power the subpanel in my detached garage.

Moving these circuits to the new panel will require splicing wires in order to reach the new panel breakers. My question is: Does NEC code allow for splices inside the circuit breaker panel? Are there special type splices needed for this situation or are wire nuts allowed? All splices will be done correctly and taped. A master electrician and electrical engineer have said it is legal but a NEC reference, page and paragraph, would be helpful incase my inspector objects.

Thanks in advance for your response. Don

  • Unless it's changed recently, it must. I've had several projects done by qualified pros and inspected that left pigtails in the box. – isherwood Feb 21 '18 at 15:51
  • They make "quadplex" breakers which allow both double-stuffing and legal 2-pole. They are notable in that the handles are tied. Untied handles should not feed any 240V circuit. Adding handle ties is not sufficient; the factory handle-ties merely reflect a mechanism inside the breaker that assures common trip. Retrofit handle ties are allowed for MWBCs as they need common maintenance shutoff but not common trip. – Harper - Reinstate Monica Feb 21 '18 at 19:06

It is legal to splice inside the service panel. I regularly have to do this when replacing the existing panel, it is quite common. Another way is to add a gutter and use that if the location of the panel is moved, code requires the splices to be in an approved or listed box that is accessible the panel is appropriate but sometimes with older panels there is not enough room to do it in a neat and workmanship manner so I add a gutter.

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    +1 for @Ed Beal - Its important to understand that a panelboard is many parts. First part it's a Cabinet. Second part is the guts that's where the busses and breakers are. Third are gutters where the conductors are. The NEC reference is Article 312.8 (A) Splices, Taps and Feed-Through Conductors which allows splicing as long as you do not exceed 75% of the CSA of that gutter space, and the feed through conductors disconnecting means location are labeled, and the conductor total does not exceed 40% fill. Worst case, you may have to present the AHJ a calculation. – Retired Master Electrician Feb 21 '18 at 19:47

I recommend you consider a simple upgrade of your main service meter/panel combo to 30 or 40 spaces. They are remarkably affordable today. You will up the value of your house far more than this costs.

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  • I agree, I just priced out a 12 slot lug-only panel and a 100A main breaker and it cost more than a nicer 30 slot with a 200A main included. – Isaac Brown Sep 12 at 21:33

While you're fitting subpanels, fit another one right next to your main. Pull as many circuits out of the main as you need to feel comfortable, get away from those lousy double-stuff panels. Leave the heaviest drawers. Good time to kick them up to AFCI or GFCI if you want that.

A 12-space panel isn't all bad, it can support six subpanels, so 252 spaces. That'll do for a ranch house.

I am just surprised a 12-space panel can support that much power. Usually a small panel means a small amp rating. For that reason subpanels should be as large (ampwise) as needed to get the desired spaces.

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  • I am cyrrently working on a brand new 125 amp panel with only 12 spaces, it is 3 phase but they make the same panel for split, so they are out there. I usually go big but this panel I only need 1 three phase and 1 single for 4 slots so 12 is more than enough for this project. – Ed Beal Feb 21 '18 at 19:52

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