5

Can I use a 60amp 240v AC service quick disconnect box, despite my romex, circuit-breaker, and AC unit being merely 30amp 240v?

I'm getting ready for a AC tech to install a split unit AC, and am shopping for a quick-disconnect service box.

Can I use one that is rated for higher amperage than I actually need?

Example of the kind of box I'm looking at: https://www.acehardware.com/departments/lighting-and-electrical/circuit-breakers-fuses-and-panels/circuit-breakers/3021409

1
  • 1
    Provided that everything is protected and fed sufficiently, can I use an enclosure rated for a higher amperage? ... "Can I use a 60amp AC disconnect box for a 30amp circuit?" No. "Can I use a 60amp AC disconnect box on a 30amp circuit? Yes.
    – Mazura
    Dec 19, 2022 at 1:41

1 Answer 1

16

TL;DR Yes

As long as there is already a breaker protecting the wire and equipment (which you indicated is the case), the disconnect is not there to provide any overcurrent protection but rather to allow for easy manual disconnect when needed. 100% fine.

4
  • 2
    To add to this, an example code reference is 440.12(A)(1) with 'The ampere rating shall be at least 115 percent of the nameplate rated-load current or branch-circuit selection current, whichever is greater.' Emphasis there on the 'at least'.
    – KMJ
    Dec 18, 2022 at 7:04
  • 3
    @manassehkatz-Moving2Codidact Your answer was just fine, I see no reason that someone should DV it. Repeatedly we've said here, usually regarding sub-panels: "Go big, you don't have to feed it at rated capacity, if you have a 100 amp sub and feed it with 60 amps, no problem as long as the feed breaker is appropriate for the wire size. I have a 200 amp panel configured as a sub in my shop fed by 125 amps, passed inspection with no issues. Hopefully the person who DV'd your answer will see this and un-do it. Dec 18, 2022 at 10:22
  • I had to read it three times to find where they said it was on a 30. "despite my romex [...] being merely 30amp 240v?" doesn't make any sense. "despite my [...] circuit-breaker [...] being merely 30amp 240v?" ah, there it is. "AC unit being merely 30amp 240v?" doesn't mean much either. Condensers have a Minimum Circuit Ampacity, and a Maximum Overcurrent Protection. And the one you should use (TM), is somewhere in between those.
    – Mazura
    Dec 19, 2022 at 1:33
  • @Mazura I am working under the assumption here that the 30A cable and breaker are not appropriately for the compressor. If they are then 60A disconnect is fine Dec 19, 2022 at 1:44

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.