Can I splice a feeder inside a panelboard?

Yes. NEC 312.8(A) permits splices and taps in a switch or overcurrent device enclosure provided conductors alone stay under 40 percent fill and conductors plus splices stay under 75 percent, with a 110.21(B) warning label for feed through conductors.

Can two neutrals share one terminal in a panel?

No. NEC 408.41 requires each grounded conductor to terminate in an individual terminal that is not used for another conductor.

Can grounds double up on the ground bar?

Only if the bar is listed and marked for more than one conductor per terminal. NEC 110.3(B) makes that marking enforceable and 250.148 permits equipment grounding conductors to be spliced.

Are splices allowed inside an electrical panel?

Yes. Splices in a panelboard enclosure are permitted, and the rule that governs them is Section 312.8(A). The myth that panels are splice free comes from older editions and from confusing a panel with a raceway.

The 75 percent rule

Section 312.8(A) of the 2023 NEC permits enclosures for switches or overcurrent devices to contain splices, taps, and conductors feeding through, provided all three of the following are met. First, the total of all conductors installed at any cross section of the wiring space does not exceed 40 percent of the cross sectional area of that space. Second, the total area of all conductors, splices, and taps installed at any cross section does not exceed 75 percent of the cross sectional area of that space. Third, a warning label complying with 110.21(B) is applied to the enclosure that identifies the closest disconnecting means for any feed through conductors.

In plain terms, you can splice in a panel until the gutter starts to get crowded. Two or three wire nuts in the side gutter of a 200 ampere loadcenter is nowhere near 75 percent. A gutter packed with twenty splices and a bundle of feed through feeders is a different story.

The splice itself has to be legal

Section 110.14(B) requires conductors to be spliced or joined with splicing devices identified for the use or by brazing, welding, or soldering with a fusible metal or alloy. Soldered splices must first be spliced or joined so as to be mechanically and electrically secure without solder, then soldered. All splices must be covered with an insulation equivalent to that of the conductors. A wire nut listed for the conductor count and size, or an insulated splice block, satisfies that.

Grounded and grounding conductors

Section 408.41 requires each grounded conductor to terminate within the panelboard in an individual terminal that is not used for another conductor. That means one neutral per hole, no exceptions, no doubling up. Section 250.148 permits equipment grounding conductors to be spliced, and many bus bars are listed for two or three grounds per terminal, which is why grounds can double up when the bar is marked for it under 110.3(B).

The working space trap

Splices that crowd the gutter make it hard to route conductors and can push against the deadfront. Section 312.7 requires the wiring space to be free of obstructions, and 110.12 requires neat and workmanlike installation. A pile of unmanaged splices behind the dead front is the fastest way to a correction notice even when the fill math technically passes.

Field takeaway

Splicing in a panel is legal. Keep the splices in the gutter, use listed connectors, do not exceed the 75 percent figure with conductors plus splices, add the 110.21(B) warning label if any conductors feed through, and give every neutral its own terminal.