location of tie-in to the grid

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fiddlehead
fiddlehead Solar Expert Posts: 29 ✭
in Grid Tie and Grid Interactive Systems #1
I have sent two separate drawings. One has an existing meter disconnect. This drawing shows what I would like to do. It uses existing equipment and will be fairly easy. Although, I think it violates article 690.64 (B) (2). I really don’t see a problem with why it would be dangerous. From reading that I’ve done, it seems like the code was trying to protect the main conductor from overload if anyone else tapped a load (or loads) from that conductor that would allow the breakers feeding it to overload the conductor.

The other drawing has the meter disconnect removed and replaced with a regular 200 amp meter. I believe this would be acceptable in code terms. The conductor just needs to be sized according to the loads it feeds (or is being fed by ). This install, while it looks easy, of course adds more money and time to the project, while also taking up more “real estate”.

These seem like practically the same install electrically. Anyone that is going to tap more conductors off from the feeder cable should be aware of what they are doing with either install.

Any thoughts on this would be most helpful.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #2
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    Re: location of tie-in to the grid

    unfortunately the thumbnails aren't very readable so you may have to describe what it is in each drawing and what specifically you are seeing as a violation so give your take on it.
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  • fiddlehead
    fiddlehead Solar Expert Posts: 29 ✭
    #3
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    Re: location of tie-in to the grid

    ok, sorry, this is my first time and I was hoping a picture would be worth a thousand words.

    Basically I would like to use an existing meter socket that has a 200 amp breaker in it. At the load side of the breaker is factory taps that go to a small busbar right next to the 200 amp breaker. From the busbar one could feed a 125 amp load (in this case a barn) and a couple of 20 amp single pole breakers.

    What if I ran 4/0 copper from the 200 amp breaker into a raintight trough for about 6 feet. From the trough I tap in with a disconnect for PV, say 150 amps, also, I tap in with a disconnect for a wind turbine, say 40 amps. So the code issue is that I could potentially be overloading that conductor with a 200 amp feed, 150 amp feed and a 40 amp feed. The reality is that it will never see more than the PV and wind feed combined. The factory taps to the loads will be far less than what the wire is able to carry. But reading through the Code, it seems this will violate the article I referenced earlier.

    Although, if I change the meter socket out and from the load side of the meter socket tap three seperate disconnects ( barn, PV , Wind ) and size the conductor accordingly ( which would not be anymore than 4/0 based on the loads), I should be code compliant? You are allowed in article 240 to have up to six disconnects for a service. Sizing the conductors is based on the loads you will have. But with PV/wind it is not a load anymore and the code does not make mention in 240 on how to size.

    Am I missing something or are these two seperate ways of doing this project about the same electrically, but one way is "code compliant" and more costly

    confused as to why there are not a few more exceptions to this rule.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
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    Re: location of tie-in to the grid

    the busses may be fine, but the fuses/breakers must be dc rated and i doubt that they are and i am assuming this is all dc passing through this and not an intermixing of dc and ac voltages. pv just does not go straight to ac as it must go through a proper grid tie inverter. or am i still misunderstanding the big picture?
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  • fiddlehead
    fiddlehead Solar Expert Posts: 29 ✭
    #5
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    Re: location of tie-in to the grid

    It is all AC voltage. I have been doing it a while, so I am not a novice. I am just concerned with the Code issue of conductor sizing on the grid tie side of things.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
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    Re: location of tie-in to the grid

    The reason for some of the "picky" aspects of electrical code is not always "will it work?" or even "is it safe?" but sometimes "what happens when the next guy come along?"

    It doesn't always help. A really determined idiot can do a lot of damage. :p

    DC equipment is different from AC mainly because direct current can 'jump' a bigger gap, as it travels in one direction only.

    I admit I can't see the thumbnail clearly and have trouble understanding your description: this is because I'm old, not because you're wrong. :D

    Curiously and possibly irrelevant: fuses work in either direction, but even AC breakers are designed with in/out connections and don't necessarily work when wired backwards. (Hundreds of design variations so don't nail me for being non-specific please!)
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  • Ecnerwal
    Ecnerwal Solar Expert Posts: 101 ✭✭
    #7
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    Re: location of tie-in to the grid

    The pictures are too small to be worth even 500 words - specifically, the words on the pictures are unreadable, so it's not clear what's being drawn. Make them big enough to read and they might be useful, and/or we might be able to make suggestions for how to make it suit code and get close to what you want, too.

    Presumably you are using grid-tie AC solar and eventual wind (why look, we are even in the grid tie section), and some folks are evidently getting confused because they are diverging into DC, which is all on the far side of the grid tie inverters in this case.
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