M.Holt's PV Book

[c_picard]

I just got my Pv book in the mail. (xmas present to myself)

Flipping through it, I was reminded of a couple of code sections that I still struggle with.

First, I'm confused by the idea that somehow a supply side tap feeding an AC service disconnect doesn't
count towards the six throws of the hand. Utility power is brought to the line side of that disco, how are those conductors not SERVICE conductors? If you had 6 disconnects labelled Main Disconnect 1 of 6, 2 of 6, etc., seems like a bad idea to have a fifth disconnect supplying power to the building's wiring, even if that wiring is only connected to an inverter. This interpretation seems to defeat what I think to be the intent of the code, which the ability to kill ALL AC power to a buildings' wiring with six throws of the hand or less.

Second , and last for now, if a DC disconnect is required at a readily accessible location nearest the point of entry, then why the mention of wiring types to be used if a disconnect is not located nearest the point of entry?
I take this to mean 'A disconnect is required, but if you'd rather not install one, put the dc conductors in something metal.'

Thanks for your input.

 

[jaggedben]

First, I'm confused by the idea that somehow a supply side tap feeding an AC service disconnect doesn't count towards the six throws of the hand. Utility power is brought to the line side of that disco, how are those conductors not SERVICE conductors? If you had 6 disconnects labelled Main Disconnect 1 of 6, 2 of 6, etc., seems like a bad idea to have a fifth disconnect supplying power to the building's wiring, even if that wiring is only connected to an inverter. This interpretation seems to defeat what I think to be the intent of the code, which the ability to kill ALL AC power to a buildings' wiring with six throws of the hand or less.

If the conductors for the PV are tapped off the existing SE conductors, they are considered a separate set of SE conductors. See 230.40 Exception no 5, which refers to 230.82(6), which include PV systems. Note that 230.40 Exception no 5 is explicitly referred to in 230.71(A) as a example of more than one set of SE conductors.

If the supply side PV connection is via a dedicated breaker in a load center, alongside one or more other breakers, then it counts as one of the six, because there is only one set of SE conductors.

I take this to mean 'A disconnect is required, but if you'd rather not install one, put the dc conductors in something metal.'

I think that's basically right. See the exception to 690.14(C)(1). Either you've got to put in a readily accessible disconnect, or comply with 690.31(E) (which, btw, includes more than merely putting it in something metal.)

Note that most people still put the DC in something metal even after a disconnect. Running PV DC in romex rubs people the wrong way, for good reasons I think. Never done it, or seen it done, even though the code seems to allow it after a disconnect. Also, since point of entry (e.g. roof into attic) is often not readily accessible, that often makes 690.31(E) a requirement anyway. Bottomline, in all jobs I've worked on we've used metal raceway for DC 100% of the time.