Listed branch-circuit overcurrent protective device

[steve66]

As a practical matter, although there are many NRTLs, only UL also develops the US standards that they all test against.
UL and some other NRTLs may also test to other (e.g. Canadian) standards just as CSA is a US recognized NRTL.

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Other than CSA, I don't think the other testing labs are ANSI standard writing organizations.

I don't want to hijack the thread with a side bar, but I'm just saying I don't think UL has any monopoly on listing equipment or writing standards. It might be a remote possibility, but it seems like it would be possible for someone else to write a standard, get it ANSI approved, and then some other NRTL could approve a particular device.