[RE-wrenches] Imbalanced Legs in 3-Phase systems

[Darryl Thayer]

I have heard the 6kW imbalance rule.  However when I spoke with the area Engineer from the Utility, he said he would not be at all concerned with 10% imbalance. in fact unless I was to exceed 20% not to worry.  The system was a 800 amp 480 volt.  He of course said my concern is more where I feed the panel to connect.  Which is the concern of the electrical inspector.  
Darryl

--- On Thu, 8/7/08, Jeff Clearwater, Village Power Design <jeffc at villagepower.com> wrote:

> From: Jeff Clearwater, Village Power Design <jeffc at villagepower.com>
> Subject: [RE-wrenches] Imbalanced Legs in 3-Phase systems
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Thursday, August 7, 2008, 12:13 PM
> Hi Wrenches,
> 
> How does one determine how much imbalance can be tolerated
> on a 3 phase system?
> 
> I'd like to feed 2 SMA SB5000s at 277 VAC into a 480
> VAC panel 
> instead of 1 13 KW Solectria at 480VAC as the PV system is
> only 9500 
> Watts STC.  The main on the backfed service panel is 600 A.
>  But I'm 
> not that sure of the loads as it's new construction and
> hasn't been 
> characterized.
> 
> What are the appropriate calcs to do here?
> 
> Thanks!
> 
> Jeff C.
> -- 
> ~~~~~~~~~~~~~
> Jeff Clearwater
> Village Power Design
> Sustainable Energy & Water Solutions for Home &
> Village
> http://www.villagepower.com
> gosolar at villagepower.com
> NABCEP (tm) Certified Solar PV Installer
> 
> Voice: 413-259-3776
> Fax: 413-825-0703
> 65 Schoolhouse Rd
> Amherst, MA 01002
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