Is double tapping a breaker a code violation?

It violates NEC 110.14(A) unless the terminal is identified for two conductors. Only some breakers, such as certain Square D QO and Homeline models, are listed for two wires.

How do you fix a double tapped breaker?

Splice the two conductors to a single pigtail with a listed connector and land the pigtail on the breaker, or add another breaker or a tandem where the panel allows it.

Can You Put Two Wires Under One Breaker Lug?

A user asked whether old Bryant Slimline breakers can take two wires under the lug. The short answer for almost every old breaker is no, and the code section that governs it is NEC 110.14(A): a terminal may serve two or more conductors only where it is identified for that use.

Identification comes from the product listing, not from whether the wires physically fit. The information is on the breaker label, the panel label, or the manufacturer literature. If the label does not say the terminal accepts two conductors, landing two wires there is a violation, and it is one of the most common defects flagged on home inspections.

Which breakers are listed for two wires

The well known exceptions are certain Square D QO and Homeline breakers rated 30 amps and less, which have a terminal designed to clamp two conductors of the same size, and some older Cutler Hammer CH types. Bryant, Zinsco, Federal Pacific, and most GE, Siemens, and Eaton BR breakers are not listed for two conductors. Old Bryant Slimline and thin twin breakers fall in the not listed group, so treat any double tap on them as a defect.

Why it matters

Two conductors under a lug designed for one do not clamp evenly. One wire ends up loose, the connection heats under load, and the cycle of heating and cooling loosens it further. Loose terminations are a leading cause of panel fires, which is why inspectors take this seriously even when the panel has worked fine for years.

The right fix

Three clean options. First, pigtail: splice both circuit conductors to a short single conductor with a listed wire connector and land that pigtail under the lug. The splice must stay inside the panel wiring gutter, which is permitted per 312.8 as long as fill limits are met. Second, add a breaker if the panel has an open space. Third, use a tandem breaker, but only in slots the panelboard is listed to accept, which the panel label diagram will show.

On an old Bryant panel, also weigh replacement. Parts are scarce, listed tandems are hard to source, and a modern load center with AFCI and GFCI protection is often the better spend than working around a 50 year old bus.

Not sure what your specific breaker is listed for? Snap the label and ask in the Ask BONBON app, and you get an answer with the code citation attached.