How to back feed a breaker as a main

Posted by LJD on January 13, 2012 at 10:37:39 from (75.251.27.156):

In Reply to: Subpanel with main breaker for barn posted by mkirsch on January 13, 2012 at 07:50:31:

Here's some recent "opinions and comments" from the code people. National Electric Code is not law - but good reading anyway.

Intalling a double-breaker in a small panel as a main is very common and allowed - even with the latest NEC "recommendations."

The write-up:

Backfed Breakers
The National Fire Protection Association (NFPA) has
issued an informal opinion that
backfed circuit breakers used to connect to a load center must be clamped.
“Clamped” means that the individual circuit breaker
must be attached to the load center back plane with a
screw or other device specifically made for the purpose
of preventing the breaker from being inadvertently
pulled loose from the bus bars of the load center. The
screw or other device is supplied by the manufacturer of
the load center. Many load centers have no provisions
for clamping, and therefore are not suitable for
backfeeding.
NEC 690.64(B)(5) requires that such breakers be
“identified” for backfeeding. According to Underwriters
Laboratories (UL), an identified breaker is one that does
not have terminals marked “line” and “load.” The
clamping requirement comes from NEC 408.16(F) in
Chapter 4 of the code, one of the general chapters. A
proposal to modify Article 690 will be submitted for
changes to the 2005 NEC. But until then, the Chapter 4
requirement is the governing requirement, since nothing
in Article 690 overrides it or even conflicts with it.
Most inspectors will accept the following reasons for not
clamping a breaker being backfed from a utilityinteractive
inverter:
• The plug-in breaker will immediately become deenergized
(dead) when the breaker is accidentally
unplugged from the load center because of the antiislanding
circuits built into the listed inverter under UL
Standard 1741.
• The front panel on most load centers actually clamps
all circuit breakers to the bus bars, and this panel
cannot be removed without a tool.
• Access to the inside of any load center connected to a
utility feeder allows an unqualified person to easily
come into contact with any exposed bus bar and the
main feeder wires.
Here are several solutions if the inspector requires that
the backfed breaker be clamped:
• Determine whether the existing load center has a kit
that can be used to clamp breakers into position, and
use that kit.
• Install a second service panel disconnect that
bypasses the existing load center, as described in
HP89. This service panel can be purchased from a
number of vendors, and has only a single breaker that is bolted in place.

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