QO Breakers and Panels [RE-wrenches]

Drake Chamberlin - Electrical Energy solar at eagle-access.net
Thu Mar 8 17:43:08 PST 2001


<x-flowed>Wrenches,

A DC rated switch would work fine.  The QO breakers are readily available, 
convenient and can be installed in weather proof enclosures.  As an array 
disconnect, I am not considering they will be useful for overcurrent 
protection.  If the system conductors and fusing are properly sized, this 
shouldn't be an issue anyway, due to the current limited nature of the array.

Breakers are not very useful for array short circuit protection due to the 
fact that the short circuit current and the charging current are not that 
far apart.  It would take a very closely adjusted, adjustable trip breaker 
to "see" the difference in most cases.  I don't think this is an option anyway.

Drake

At 12:28 PM 03/08/2001 -0800, you wrote:
>Colleagues:
>
>I just finished a telephone call with Square D tech support.  They are
>going to fax me critical information which I will share as soon as it
>arrives and I have time to transcribe it.
>
>I have a question about Drake's post, below:
>
>
>At 10:03 AM 3/8/01 -0800, you wrote:
> >Hi Bill,
> >
> >
> >What ever the reason might be, it convinced me that fuses are superior
> >protection to breakers.  As you stated before, the QO breaker makes an
> >excellent switch for low voltage DC.  I think it is good for PV array
> >disconnects, as they are current limited.  On the battery side, I don't
> >trust the QO as the sole protection.
> >
> >Drake
>
>Q: If we are using a DC rated circuit breaker to connect PV source circuits
>to a battery charging system, then don't we have a battery connection at
>the load side?  For example, in a TC60 with breaker option with the breaker
>wired in the output circuit: the breaker will be connected to the battery
>bank.  In this case then, one should always install a fuse between the
>breaker and the batteries, correct?  Then why even have a breaker?  Why not
>instead use a switch with adequate interrupting capacity?  See ASCII CAD
>below:
>
>Typical PV source and charging circuit:
>
>PV array---DC breaker-----\
>                                        ----Charge
>control---Switch-------fuse--batteries
>PV array---DC breaker-----/
>
>
>Thanks again for the great dialog.  We need these answers so we can design
>reliable and legal installations.
>
>
>William
>
>__________________________________________________________________
>William Miller
>SLO Communications: Communications and Power Systems Consulting
>PO Box 50, Santa Margarita, CA 93453
>Voice :805-438-5600             Fax: 805-438-4607       VMail: 805-546-4875
>email: wrmiller at slonet.org
>License No. C-10-773985
>_____________________________________________________________
>Compatibility:
>Word processor: WP7
>Spreadsheet: Quatro Pro 7
>CAD: Microstation 95, DXF, Visio 4.1T
>_____________________________________________________________
>"I stand by all the misstatements that I've made." Dan Quayle
>__________________________________________________________________
>
>- - - - - - -
>To send a message:
>  RE-wrenches at topica.com
>
>The archive of previous messages:
>  http://www.topica.com/lists/RE-wrenches/
>
>List rules & etiquette:
>  http://www.mrsharkey.com/wrenches/etiquete.htm
>
>To unsubscribe send a message to:
>  RE-wrenches-unsubscribe at topica.com
>
>To check out the other RE-Wrench participants:
>  www.mrsharkey.com/wrenches/index.html
>
>Hosted by Home Power magazine:
>  www.homepower.com
>
>For info contact list moderator by email:
>  michael.welch at homepower.com
>
>____________________________________________________________
>T O P I C A  -- Learn More. Surf Less.
>Newsletters, Tips and Discussions on Topics You Choose.
>http://www.topica.com/partner/tag01

- - - - - - -
To send a message:
 RE-wrenches at topica.com

The archive of previous messages: 
 http://www.topica.com/lists/RE-wrenches/

List rules & etiquette:
 http://www.mrsharkey.com/wrenches/etiquete.htm

To unsubscribe send a message to: 
 RE-wrenches-unsubscribe at topica.com

To check out the other RE-Wrench participants:
 www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine: 
 www.homepower.com

For info contact list moderator by email:
 michael.welch at homepower.com

____________________________________________________________
T O P I C A  -- Learn More. Surf Less. 
Newsletters, Tips and Discussions on Topics You Choose.
http://www.topica.com/partner/tag01

</x-flowed>



More information about the RE-wrenches mailing list