Photo voltaic system question

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my question is.. when the conductors from a photo array are installed in a metal raceway, and enter a single family residence, to a REMOTE inverter, is a disconnect required either outside or immediately inside the house to disconnect the array conductors? It seems to me that you should be able to disconnect these conductors in case there is a fire or for maintenance purposes. Is there a reqirement to install a DC fused or unfused disconnect in the array conductors before they enter the house?
 
Photo voltaic

Photo voltaic

yes, i know that. my question is, " do you need a DC disconnect on the outside of the house to shut the array down, or does the joiner box serve as the disconnect?
 

iwire

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yes, i know that. my question is, " do you need a DC disconnect on the outside of the house to shut the array down, or does the joiner box serve as the disconnect?
No you do not need a disconnecting means outside if the interior potion is run all the way to the DC disconnect with metal raceway.
 
Photovoltaic

Photovoltaic

ty for that. just to clarify this a bit. 1 last question. Does the combiner box
on the roof need to have disconnect means to shut the array off from the conductor run? and does it need to be fused? this is where i am stuck. It seems to me that there should be some way to shut the array off from the
conductors that enter the house. TY again .
 

iwire

Moderator
Staff member
No, the NEC does not require any disconnecting means be located at the array as long as your running metal raceway inside.

And ask as many questions as you want, that is what the forum is here for. :smile:
 

cpal

Senior Member
It appears to be undersood with in the PV community that the array is producing an EMF all the time. It is my understanding that you need to cover each panel to stop it from producing an EMF. But I have never attempted this to confirm.

be careful!
 

iwire

Moderator
Staff member
It appears to be undersood with in the PV community that the array is producing an EMF all the time. It is my understanding that you need to cover each panel to stop it from producing an EMF. But I have never attempted this to confirm.

be careful!
That is true, and many commercial arrays will be operating close to 600 VDC.

The upside is the fault current is very low so while you can defiantly get electrocuted, arc flash is not as big of a concern as it is with utility supplied power.
 

cpal

Senior Member
Bob
I seem to recal that you have doine some larger arays,

Who installed the structural support for the panels ??, (are you aware of the issues with the board of examiners??
 

iwire

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Staff member
Bob
I seem to recal that you have doine some larger arays,
I completed a 50 KW and a 15 KW, I also was well underway with a 500 KW system but the money evaporated and the job was canceled.

I have also done a lot of design work for proposals. A solar guy gives me a print with his ideas for particular site and I go over it and make it work within the NEC rules.

Who installed the structural support for the panels ??,
On the 50 KW we did, but a engineer signed off on our plan before we started. The 500 KW system would not have been secured to the building at all, it would be a ballasted system and an engineer verified the roof could support the added loading.

(are you aware of the issues with the board of examiners??
No, fill me in.

I hope the board is cracking down on the unlicensed installers. :mad:
 

Besoeker

Senior Member
That is true, and many commercial arrays will be operating close to 600 VDC.
Yes, quite. And for that reason alone, I'd be inclined to fit a breaker close to the PV panel regardless of whether it is a mandatory requirement.
 

iwire

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Staff member
A circuit breaker for electrical isolation, not overcurrent protection.
Just making sure. :smile:

In that case I question the need or practicality of locating the switch up at the array that can only be accessed by ladder. I am happy the NEC recognizes this.

As it stands now If I had to kill the conductors entering the building the procedure would be to open the DC disconnect inside the building (remove the load) then I could go up on the roof and either open the individual strings at the combiner box or open the circuit using the required shielded plug style connections at the panels.
 

Besoeker

Senior Member
Just making sure. :smile:
Whatever the intent, it didn't come across that way.

In that case I question the need or practicality of locating the switch up at the array that can only be accessed by ladder. I am happy the NEC recognizes this.
I wasn't suggesting it as the only point of isolation.
As it stands now If I had to kill the conductors entering the building the procedure would be to open the DC disconnect inside the building (remove the load) then I could go up on the roof and either open the individual strings at the combiner box or open the circuit using the required shielded plug style connections at the panels.
Given that you're going to get on the roof anyway, opening a single local switch would be simpler, wouldn't it?
 
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dbuckley

Senior Member
Wasn't there a thread here a while ago that (scratching memory cells) the AHJ wanted a remote controlled isolator on the roof by the panels, with a button by the existing service entrance?
 

newenergy

Member
The NEC doesn't call for a disconnect before entering the structure, but some of the cities that I work in do require it. A combiner which breakers or no-touch fuse holders has satisfied some cities, but others have wanted a disconnect.

Not what you were asking but, if you combine 3 or more strings they need to be fused.

Modules produce voltage whenever exposed to light. In a small installation I don't think a dangerous (unless it gets your eye) arc flash is possible as the modules are current limited. I have seen some big melted equipment from an incorrectly wired large commercial array.

Regarding iwires comment about ladders, I think it's probably the fire departments that have driven the requirement (when there is one) for a disconnect on the roof. When they have that requirement they want the simplest and most visible way to disconnect the system. Most cities i've worked in haven't required a disconnect though.
 

davedottcom

Senior Member
if you combine 3 or more strings they need to be fused.
Hey newenergy, that's true unless you have mutiple inverters with only 2 strings on each inverter, right?
(The multiple DC strings are isolated from each other through the inverters)

When you say "fused", are you saying the DC circuit breakers in a combiner box are not acceptable? or do you mean they just need overcurrent protection (either fuses or breakers)?
 
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