JustCheckin

Well said Doug and others, I'm currently advising that if there is any doubt or issue, just get a breaker that matches those listed on the panel. If they're no longer available because the panel is old, then some research is necessary to see if anyone has solved that particular problem. It can't hurt to ask the AHJ what will work for them - you might even get a constructive answer. Google has a huge list of images of substitution charts which I haven't reviewed. It appears that this will forever be a bit of a sticky wicket. I have learned from this thread of some less that obvious incompatibilities to watch for. As I've now read through a lot of info on this issue, I'm thinking that a private inspector should always mention the odd breakers as a possible code violation with a caveat that relevant incompatibilities might exist and the parties should consult a licensed electrician, thereby passing off the responsibility to others hopefully more knowledgeable and again hopefully avoiding a lawsuit should a fire or other event occur.

From a Forensic Electrical Engineer and Electrical Contractor perspective, here's the background: The National Electrical Code (NEC) requires that all equipment installed in a building electrical system be "listed" and marked by an appropriate certifying agency, usually UL or CSA. To get listed, a manufacturer submits some sample products with their specifications to the agency who then performs some standard tests for overheating, etc. For breakers, the tests for the listing include installation in a specific panel, so the listing applies to certain breaker-panel combinations, thus the list of acceptable breakers stuck to the panel cover. Then that manufacturer and model number, of circuit breaker/panel in our case, becomes listed, for purposes of that NEC requirement. A jurisdiction, city, county, state, incorporates codes, like the NEC (plumbing, building, safety, etc) into their body of law. The NEC is only applicable and enforceable if adopted by an "authority having jurisdiction," known as the AHJ in the NEC. To you and I, that's the (city) building or electrical inspector, and per the NEC, s/he has the final interpretation of the relevant code. S/he requires that the circuit breakers be listed, meaning that their model number be found on the label of the panel in which they have been installed. Of course, each manufacturer only pays for the test for their panel- breaker combinations. Even though the breakers might be readily interchanged physically (and may even be exactly the same mechanically and electrically), the testing agency will only certify those whose names match up, and for which they have been paid. What with manufacturers buying each other, the advent of the big box depot, and efficiency of space usage, some manufacturers have paid to have their breakers tested in the panels of several others, and can then offer that breaker to a chain to solve all replacement requirements of its customers in less display space. (Some breakers are physically incompatible and no test protocol will make them fit. Obviously its the ITE, Bryant, GE, Eaton, Westinghouse, Cutler Hammer, SquareD HOM, etc style that we find most often swapped. Zinsco, ITE/Bulldog, FPE/Stablok are all physically unique and not candidates for interchangeability.) Just because one manufacturer buys another and their breakers physically interchange doesn't automatically mean that they are now code acceptable. You may find that the inspector rejects, for example, an older ITE (not labeled properly for interchange) and accepts a newer ITE (which, if labeled for other brand panels, implies that it has been tested for those panels, even if, in fact, there has been no manufacturing or specification changes!) Is this fair? The inspector has reasonable assurance of a safe installation if he follows the protocols of the NEC. As we see in other posts, there may be an acceptable interchangeability chart that can be pasted into an old panel that will satisfy the inspector, and perhaps we should all keep some of those around.