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This breaker operates pool equipment outside. It buzzes when under load, so I think I should replace it. Can’t find it online, Any suggestions on what to use in it’s place? YF-6738 breaker Eidt: my box is not T&B like in this question: Compatibility for Thomas & Betts breakers

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    Can you post photos of the labeling on the inside of the panel's door please? It could be that this T&B was never the correct thing to begin with...
    – ThreePhaseEel
    Sep 18 at 3:00
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    In a quick search, it looks like the problem is you have a tandem/half-size breaker, and it looks like the Eaton classified breakers are only the full-size breakers. But (assuming this is even the correct breaker type, as ThreePhaseEeel noted may be an issue) you may well have enough space to put in full-size Eaton replacements. So a picture of the full panel, as well as the labeling, is needed to figure this out.
    – manassehkatz-Moving 2 Codidact
    Sep 18 at 4:04
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    The label confirms what ThreePhaseEel suggested: that breaker does not belong in that panel and the breaker clip/bus mismatch may well be the cause of the buzzing. You should have a listed Murray breaker, successor Siemens breaker (see s3.amazonaws.com/dcc-data-extract/new-delta/asset/Compas/daily/…), or other properly classified breaker (such as Eaton CL). You may need to replace the whole panel now if the bus is damaged.
    – nobody
    Sep 19 at 1:15
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    I have a funny feeling about what may be going on here. Can you check (carefully!) voltage between the red hot and neutral, between the black hot and neutral and between the red and black hots? Theory: Originally had four full-size Murray breakers, so 2 (outer) on A=red and 2 (inner) on B=black. Something went wrong. Rather than fix the original problem, shoved tandem breakers (of a different not 100% compatible brand...) in so that everything could be on A=red.
    – manassehkatz-Moving 2 Codidact
    Sep 19 at 1:21
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    Also given that there are four hot wires hooked up to breakers and only three neutrals on the neutral bar, there is probably at least one mis-phased multi-wire branch circuit at risk of lighting its neutral on fire (but not the cause of the breaker buzzing).
    – nobody
    Sep 19 at 2:30

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The buzzing is a sign of an alien (breaker) invasion!

Your panel is a Murray panel from the Siemens era, which means that it uses Siemens breakers as the corresponding Murray part numbers (same breaker, different paper label) were discontinued a few years ago by Siemens in order to regularize their product line. As a result, I'd check the multi-wire branch circuit situation out first to avoid a slow-cooked neutral; worse comes to worse, you can nut the black and red wires from that circuit to a 12AWG pigtail to a single breaker, provided the circuit's loading permits that of course.

Once that's resolved, we can take care of the buzzing. The existing breakers are Eaton BR (BD) and T&B (similar to Eaton), and the T&B in particular isn't quite fitting right into the Murray panel you have, hence the noises, which are a sign of arcing and potential damage. If the busbar stabs are still good when you pull things out, you can replace the alien breakers with a Q120 and a Q2020, deporting them from your panel for good.

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