[RE-wrenches] QO Breakers ok for Back feeding?

[William Korthof]

As I understand it, "backfed" referred to the source of energization. Current flow alternates both ways at line frequency regardless of the direction of power flow. The reason for marking "line" and "load" is because the source of energization remains powered when the device is turned off. In the case of fused disconnect switches, connecting a source to the load side results in the fuses being energized at all times. 
With circuit breakers, the intent of line/load distinction was so that source breakers require more than simply being pulled on before they come. Unfastening a screw that secures the backfed breaker for example...
It doesn't make sense to lump grid interactive solar with sources of energization (generators, grid power...) because we have special rules for interactive solar---UL1741...  

/wk


On Sep 16, 2014, at 3:53 PM, "Glenn Burt" <glenn.burt at glbcc.com> wrote:

Also 705.12(D)5 in 2011:
(5) Suitable for Backfeed. Circuit breakers, if backfed, shall be suitable for such operation.
FPN: Circuit breakers that are marked “Line” and “Load” have been evaluated only in the direction marked. Circuit breakers without “Line” and “Load” have been evaluated in both directions.
 
705.12(D)4 in 2014:
(4) Suitable for Backfeed. Circuit breakers, if backfed, shall
be suitable for such operation.
Informational Note: Fused disconnects, unless otherwise marked,
are suitable for backfeeding.
 
-Glenn
 
From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allen Frishman
Sent: Tuesday, September 16, 2014 5:48 PM
To: re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] QO Breakers ok for Back feeding?
 
Wrenchers,
One of my associates was asked by an inspector to prove that the QO breaker is rated for back-feeding.    I seem to remember the code stating that as long as the breaker does not state that it is only rated for one direction then it is ok to back feed. 
 
Anyone have a reference to the code or literature from Square D that states it is ok to back feed?
 
All feedback is appreciated.
Al Frishman
AeonSolar
(917) 699-6641 - cell
(888) 460-2867
www.aeonsolar.com
 
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