Switching Array leads[RE-wrenches]

[David Brearley]

The system in the HP article uses a transformerless inverter...so both
current carrying conductors are ungrounded.

David C. Brearley
Operations Manager
NABCEP Certified Solar Installer 
 
Meridian Energy Systems, Inc. (TECL: 24461)
2300 S. Lamar Blvd., Ste. 107
Austin, Texas 78704
P: 512-448-0055
F: 512-448-0045
david at meridiansolar.com
www.meridiansolar.com
 

-----Original Message-----
From: Drake Chamberlin [mailto:Drake.Chamberlin at redwoodalliance.org] 
Sent: Saturday, July 28, 2007 4:02 PM
To: RE-wrenches at topica.com
Subject: RE: Switching Array leads[RE-wrenches]


The ungrounded conductors must be switched.  In some systems ( I 
think under 50 volts) it is still permissible to not have a grounded 
circuit conductor, but to switch both.   I believe it is code to 
break the grounded conductor with a switch, so long as the ungrounded 
conductor breaks at the same time.

Drake


At 06:39 AM 7/28/2007, you wrote:

>As I recall, the older code required both the positive and negative 
>leads of an array to be switched at the array dis-connect. I think 
>at the time there was no DC ground fault required and most of these 
>were low voltage arrays. More recently, I believe the code indicates 
>only the "un-grounded" lead to be switched, which would imply just 
>the positive lead. Since we now have ground fault circuits I think 
>this may also be related to the ground fault working properly since 
>it needs to "see" the potential between the grounding conductor and 
>the negative before it is grounded.
>
>However, in the recent issue of HomePower there is a system showing 
>both the positive and negative leads being switched at the array 
>dis-connect. Am I wrong and this is not code, ground fault, or high 
>voltage related issue and it is up to the installer? Since all 
>dis-connects are either 2 or 3 pole, it is not a cost issue, so 
>under what (if any) circumstances would you switch only the positive 
>and allow the negative and array frame grounding conductor to pass 
>through the dis-connect.
>
>Thanks,
>
>Jeff Yago


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