NEC 110.3(B) and The Intermixing of Circuit breakers.

Over the years, maintenance persons have had their way with this panelboard. The panelboard had circuit breakers from different manufacturers as well as both 10k AIC and 22k AIC circuit breakers.
Click to Enlarge
Over the years, maintenance persons have had their way with this panelboard. The panelboard had circuit breakers from different manufacturers as well as both 10k AIC and 22k AIC circuit breakers.

On the labels of most electrical panels will be the following wording or equivalent: “THE SHORT-CIRCUIT CURRENT RATING OF THIS PANELBOARD IS LIMITED TO THE LOWEST AIC RATING OF ANY INSTALLED CIRCUIT BREAKER”.

When the circuit breakers in a panelboard are selected as part of a series rated combination, the combination determines the overall short-circuit current rating of the entire panelboard. If the series rating chart shows that the main circuit breaker with an AIC rating of 42kA and branch circuit breakers with an AIC rating of 22kA are part of a series combination rated together at 42kA, for example, then installing a 10kA circuit breaker in the panelboard by mistake would void any series combination rating established previously between the 42k AIC main breaker and the 22kA AIC branch breakers.

As well, series combinations between circuit breakers will always be of the same manufacturer. One will never find a series rated combination between a GE main breaker and a Square D branch breaker unless the two companies merge and do some additional testing for compatibility. Neither company has the desire or financial interest to submit their circuit breaker to a testing lab and test it as a combination with another manufacturers circuit breaker.

Installing a GE circuit breaker in a Cutler Hammer electric panel just because it fits doesn’t mean it’s right. Any previous series rated combination in such a panelboard would no longer be valid if a different manufacturers circuit breaker has been installed. Using another manufacturers circuit breaker in the wrong panelboard violates NEC 110.3(B) and violates the product listing.

See the actual NEC text at NFPA.ORG for the complete code section. Once there, click on the “free access” tab and select the applicable year of NFPA 70 (National Electrical code).

2017 Code Language:

110.3(B) Installation and Use. Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling.

2020 Code Language:

110.3(B) Installation and Use. Equipment that is listed, labeled, or both shall be installed and used in accordance with any instructions included in the listing or labeling.

Did You Like This? Let Us Know With A Like! Thanks!

NEC 110.3(B) and The Intermixing of Circuit breakers.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true?

A: Installing the wrong circuit breaker in a panel is fine as long as it fits.
B: Installing the wrong circuit breaker in a panel, even if it fits, violates the product listing.
C: Two different manufacturers circuit breakers are common in a series rated system.
D: The panelboard SCCR is equal to the highest AIC rating of any installed breaker.
Please register or sign in for electrical continuing education courses.

If you were already signed in, your session probably expired, please sign back in.