[RE-wrenches] Disconnect BOTH positive and negative conductors from array?!?

[Kent Osterberg]

Most often it is the negative wire that is grounded, but not all of the 
time. Whichever is grounded should have white or light gray insulation 
and it should have a mechanical connector or bus bar connection in the 
disconnect switch so that the grounded conductor can be opened for 
maintenance. While that is what the code says, I don't feel a small 
array is any more dangerous if both conductors are switched. Quite the 
opposite: the array is "probably" safer if both conductors are open.

For an ungrounded array, which will probably become more common as 
equipment is designed to operate that way, both conductors are supposed 
to be switched in the disconnect. In that case there shouldn't be any 
white wire going to the PV array.

Kent Osterberg
Blue Mountain Solar, Inc.
www.bluemountainsolar.com
t: 541-568-4882


On 9/14/2012 6:46 PM, Bob Clark wrote:
>
> Kent:
>
> In a normally grounded array, the grounded conductor is the negative 
> conductor, right?  So, no disconnecting the negative conductor.  It 
> should go straight through the DC disconnect and on to the inverter.  
> Correct?
>
> *Bob Clark*
>
> */SolarWind Energy Systems, LLC/*
>
> *P.O. Box 1234*
>
> *Okanogan, WA 98840*
>
> *(509) 826-1259*
>
> **
>
> /Although no trees were killed in the sending of this message, a large 
> number of electrons were terribly inconvenienced.///
>
> cid:822514723 at 19022009-0502
>
> *From:*re-wrenches-bounces at lists.re-wrenches.org 
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Kent 
> Osterberg
> *Sent:* Friday, September 14, 2012 5:00 PM
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] Disconnect BOTH positive and negative 
> conductors from array?!?
>
> See 690.13. There must be a means to disconnect all conductors of a PV 
> system. If it is a normally grounded array you are not allowed to put 
> a switch in the grounded conductor, except .... for circumstances 
> added in the 2011 code.
>
> Kent Osterberg
> Blue Mountain Solar, Inc.
> www.bluemountainsolar.com  <http://www.bluemountainsolar.com>
> t: 541-568-4882
>
> On 9/14/2012 4:39 PM, Bob Clark wrote:
>
>     Wrenches:
>
>     A local utility person has suggested that both the positive and
>     negative conductors from a solar array should be disconnected.
>
>     Disconnect both or not?  2008 NEC supporting citation please.
>
>     Thanks for your response.
>
>     *Bob Clark*
>
>     */SolarWind Energy Systems, LLC/*
>
>     *P.O. Box 1234*
>
>     *Okanogan, WA 98840*
>
>     *(509) 826-1259*
>
>     **
>
>     /Although no trees were killed in the sending of this message, a
>     large number of electrons were terribly inconvenienced./
>
>     cid:822514723 at 19022009-0502
>
>     *//*
>

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