[RE-wrenches] 30 amp disconnect/40 amp breaker

[Blake Gleason]

Typically a fused disconnect can only handle 80% of it's nominal current on
a continuous basis.  Unfused disconnects are often 100% rated.  For
example, see attached Square D bulletin #3110DB0401R0410.

So, a 100% rated (unfused) 30A disconnect (at least, from Square D) should
be fine here, as long as your OCPD is provided elsewhere (eg, the breaker
you mentioned).

NEC 690.8(B)(1)(Exception) explicitly allows a 100%-rated device to be used
without multiplying the inverter output current by 125%.


On Wed, Aug 21, 2019 at 3:22 PM Greg <greg at remotepowerinc.com> wrote:

> Fellow Wrenches,  I'm having a discussion with a utility engineer
> regarding the following situation:
>
> Installing a 6kW inverter that has a full rated output of 25 amps.  80% of
> 30 is 24.  That means to me I need to go up to a 40 amp breaker.  I'm
> running #8 (continuous load 25 x 1.25 etc.)
> The engineer believes I should use a 60 amp disco since it's on a 40 amp
> breaker.  My thinking is I can use a 30 amp disco since it can not produce
> more than 25 amps ever.
>
> Do any of you have a reference that shows what I'm doing is okay? Not
> okay?
>
> Thanks again,
> Greg Egan
> Remote Power Inc.
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-- 


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*Director of Innovation & Technical Excellence*


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