# 1000VDC Spacing Specs?



## HARRY304E (Sep 15, 2010)

TinkerEngineer said:


> Ok, we are building combiner boxes for photovoltaic (PV) systems and I cannot find anything on how far busbars, energized parts, etc. need to be away from grounded items, ie panel board, enclosure, enclosure bolts, etc. These energized parts would be fed from fused feeders coming into the combiner busbar and a single conductor leaving the busbar to an appropriately sized disconnect switch. Again, the voltage is 1000VDC (707V rms). What clearance do I need for the busbars away from grounded parts?
> UL 508A only is applicable up to 600V and I'm a bit stumped.
> 
> Any help would be greatly appreciated!!


Take a look at this link it may help you...http://www.cooperbussmann.com/pdf/7a54ea38-682e-4742-843a-dd75ff0b1fbc.pdf

Welcome to the forum...:thumbsup:


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## drsparky (Nov 13, 2008)

TinkerEngineer said:


> Ok, we are building combiner boxes for photovoltaic (PV) systems and I cannot find anything on how far busbars, energized parts, etc. need to be away from grounded items, ie panel board, enclosure, enclosure bolts, etc. These energized parts would be fed from fused feeders coming into the combiner busbar and a single conductor leaving the busbar to an appropriately sized disconnect switch. Again, the voltage is 1000VDC (707V rms). What clearance do I need for the busbars away from grounded parts?
> UL 508A only is applicable up to 600V and I'm a bit stumped.
> 
> Any help would be greatly appreciated!!


I am confused on what you are trying to state. RMS is a factor of sinusoid wave forms, not DC.


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## TinkerEngineer (Feb 10, 2011)

Drsparky, you got stuck on a minor detail and overlooked the real issue. A detail which my over zealous fingers typed in. Forget the "(707V rms)". I was offering the AC equivalent but used the wrong equation in my head. Sorry.

Let me ask the question, "What clearance do I need for the busbars away from grounded parts?" in a little different way.

Table 10.1 and 10.2 in the UL 508A offer "live part" clearances for up to 600V. Is there something that offers specs on clearances for 1000-1500V?

Again, Thanks for any help!


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## JRaef (Mar 23, 2009)

TinkerEngineer said:


> Drsparky, you got stuck on a minor detail and overlooked the real issue. A detail which my over zealous fingers typed in. Forget the "(707V rms)". I was offering the AC equivalent but used the wrong equation in my head. Sorry.
> 
> Let me ask the question, "What clearance do I need for the busbars away from grounded parts?" in a little different way.
> 
> ...


No, because UL considers anything over 600V to be "Medium Voltage" and the only spec then have for that is for switchgear, and you do NOT want to use a switchgear spec for a combiner box.

Bottom line, you can't UL list that box anyway, so it's down to "best practices".

But there is another issue anyway, that being "Is spacing specified at all?"
The NEC is all about installation, not factory construction. Factory construction is what is regulated by people like UL, but in this case it no longer applies. Now we get into, "Did it pass testing?" and that's the most important thing. 

Read this paper from Powell Switchgear, a MV equipment mfr. It lays out the issue very well and has some "suggested" guidelines, but the man point is testing and passing. The test procedures you would adhere to can be found in _ANSI_/IEEE C37.41 for "high voltage" switchgear (their words) defined as 1000V and above.


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## TinkerEngineer (Feb 10, 2011)

Thanks JRaef.

From what I can piece together in my memory of my previous work-place, that sounds about right. 
Regarding the enclosures, there are ways around the 1000V UL rating! 

Thanks!


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