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

[Brian Mehalic]

I agree Blake - you have to check the specs and consult the mfg. The same is true with combiners, some are rated for continuous duty/full load, and some are not. Lots of large systems out there with 200A combiners connected to 250A OCPDs (and 250A conductors, but that’s another story...). 

Brian

> On Aug 21, 2019, at 5:20 PM, Blake Gleason <blake at sunlightandpower.com> wrote:
> 
> 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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