PV AC disconnect

[Ken Forest]

hi there,

i am working on a project that is on hold while we wait for a delayed AC combiner box (eaton 600A 3 phase). the manufacture just told our distributor that the equipment won't be ready til December. we quickly had to adjust the design, by putting three 200A or one 200A and one 400A, both totalling 600A (12 of 50A AC output breakers).
while we wait for an electrical engineer's approved stamp, i am wondering how i can land two different size conductors be landed on the load side of the 600A disconnect, and where i can find a reference in the code book to see if that's a safe wiring method. while I appreciate all your response/input, i am going to ignore all irrelevant questions like "why didn't you install one large inverter instead?"

 

[jaggedben]

Sounds like you want to do taps. See 240.21(B).

You can probably either get the disconnect to have multiple lugs or tap the conductors downstream of it. Doesn't make any difference to the rules.

 

[electrofelon]

So you have a 600A disconnect, and want to come off of that to say a 200 panel and a 400A panel? Are the panels MB or MLO? They would need to be MLO per 408.36 and the tap rules. The conductors would need to comply with the tap rules also.

600A equipment often has only two port lugs which I find annoying, but you can make it work with large copper.

 

[ggunn]

So you have a 600A disconnect, and want to come off of that to say a 200 panel and a 400A panel? Are the panels MB or MLO? They would need to be MLO per 408.36 and the tap rules.

I'll have to go look at that reference, but it doesn't seem to make sense that the panels would be required to have no OCPD. Why would that be?

 

[electrofelon]

I'll have to go look at that reference, but it doesn't seem to make sense that the panels would be required to have no OCPD. Why would that be?

Oops sorry, typo. They couldn't be MLO, would have to be MB.

 

[ggunn]

Oops sorry, typo. They couldn't be MLO, would have to be MB.

Ha! That makes more sense.

 

[Ken Forest]

Thanks all for your input, esp. the code reference.
i feel good about running three 3/0 in three different conduits (one for 200A and the other two parallel for 400A and landing on the load side with three port lugs.