Does Continuous Use Adjustment Apply to Equipment? (2023 NEC)

[BarklieEstes]

Good afternoon,

One of our project managers who has a design with 56a of inverter output asked me if he can use #4 with a 60a disconnect (Siemens LNF222RA), and a 70a backfeed breaker. I told him no but can't actually find the code that disallows it. 690.8(B) requires conductor upsizing. 690.9(A) requires OCPD upsizing. Where is equipment upsizing required? The best thing I could tell him was the blades on the disconnect are technically conductors and thus would fall under 690.8(B) but I have little confidence in that answer.

Regards,
Barklie Estes

 

[Eddie702]

#4 copper sounds ok. 60 A disconnect will not fly.

 

[jaggedben]

I actually think a greater than 60A disconnect is not strictly required by any code section, but if you look at the label of your 60A unfused disconnect you will likely find it contains an instruction to protect it with an overcurrent device not greater than 60A. And thus you'd be violating 110.3(B). Speaking from experience when I tried this once or twice in the past.

 

[BarklieEstes]

Thanks Ben. You're a smart fellow. There does appear to be a bunch of rules about OCPD sizing on the label (see attached), but the only maximum amperage limitation for OCPD appears to be for circuits with 100,000a interrupting ratings. For 10,000a interrupting rating, there doesn't appear to be such a limitation.

 

[jaggedben]

Yeah, that's interesting no? That label might be a bit different than the ones I saw in the past. But if we're parsing the exact wording on the label you show I think it's still a bit of a grey area. The switch doesn't have a continuous rating lower than the max rating, and Art 404 doesn't weigh in with anything more specific. The only counterargument I know of is the one you started with, that the switch is a conductor (dictionary definition that the NEC doesn’t elaborate on).

 

[BarklieEstes]

Very. Protecting a 60a switch with a 70a breaker seems off but doesn't look to be explicitly prohibited. Nice to have some verification that I'm not missing anything.