Supply Side Connection via a PV Dedicated Subpanel

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GoldDigger

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Smart $, all of your arguments address only that my suggested interpretation does not make sense.
What I am saying is that the separated load example does not make sense either, but we accept that it is what the code requires.
So, I will only accept arguments about the clear or unclear language of that code section. :)
 

Smart $

Esteemed Member
Location
Ohio
Smart $, all of your arguments address only that my suggested interpretation does not make sense.
What I am saying is that the separated load example does not make sense either, but we accept that it is what the code requires.
So, I will only accept arguments about the clear or unclear language of that code section. :)
I can't with argue that... :lol:

But just so you know, I'm not arguing that your interpretation doesn't make any sense. I'm arguing that it doesn't make any difference in the application of 310.15(B)(6), or (7) in later editions.
 

jaggedben

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Northern California
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Solar and Energy Storage Installer
No, but it is also supplying some or all loads instead of the feeder providing that current. How is that different from another wire supplying those loads? At least in the exact wording of the code section?

The purpose of the section is allow some savings when the load factor is low. It simply makes no sense whatsoever to argue that the load factor is changed by adding an interconnected source at the opposite end. It is different from 'another wire' supplying those loads in the sense that such an 'other wire' (i.e. a feeder that does not supply the whole dwelling) would likely have a higher load factor.

There is one situation where I would say that you do have to upsize a feeder that was sized to 310.15(B)(6). That's if the inverter output exceeds the straightfoward rating of the feeder. A pretty unusual situation, but possible.

I suppose you can make the argument that if at any specific point in time the feeder supplies all loads the section applies.

Exactly.

Otherwise you would also have problems if an alternate power source and transfer switch is involved.

That's a totally different situation.
 

GoldDigger

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Location
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I assert that it is not a different situation in that if I have a feeder to a main panel and a feeder from it to a transfer switch and critical loads panel, then the first feeder is not always supplying the entire dwelling load. Just the same as the situation where a GTI downstream of the feeder supplies some of the load current.
The only relevant difference is that in the first case you can identify specific loads that are not being powered, while in the second case the additional power source just contributes to a common pot.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
I still say you (and the plans examiner) are reading 230.42(B) wrong. It simply means that for installtions that do not fall under 230.79(A) through (C), the minimum ungrounded conductor ampacity is 60A. 230.79 says the minimum rating of the disconnect must be 60A, regardless of what it is fused. But that does not apply to SE conductors or disconnecting means connected thereto that are rated greater than 60A. If this were the case, there's be no point in having 230.90(A) Exception No. 2.

I'm going to backtrack on my previous statement and agree with Smart$ on this.

To repeat, what the code actually says is "not less than the rating of the service disconnecting means specified in 230.79A through D." The rating of the equipment that actually gets installed is not what is being referred to here.

In other (load side) installations, the rating of disconnect equipment must be equal to or greater than the circuit conductors. It makes no sense to require the opposite with service disconnecting means.

#4 wire is good. A 75A rated disconnect would also be good if you could find one.
 
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