August,
The 60A breaker is intended to allow grid power to pass through to
the loads in excess of the inverter's stand-alone output. The
point of 705.12 (moved in the 2011 NEC from 690.64 (B)(2)) is to
differentiate between load pass-through current and sell current.
The amount of current fed into the grid is (4500/230 =) 19.56A,
while the amount that can be taken from the grid and passed
through to the load is much greater. If you were limited to a 40A
breaker in order to maintain 120% of a 200A main bus, you'd be
prone to nuisance trips under large cumulative loads.
Allan
Allan Sindelar
al...@positiveenergysolar.com
NABCEP Certified Photovoltaic
Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com
On 2/27/2013 4:23 PM, August Goers wrote:
Jeremy,
Good point.
Even under the 2008 NEC 690.64(B)(2) you can install up to a
40 Amp breaker on the load side as long as it is on the
opposite side of the input feed per 690.64(B)(7). Garrison,
do you need a 60 A breaker?
I haven't used
this product myself, but if the continuous output power is
indeed 4500 W then you'd be fine with a 25 or 30 A breaker.
Best,
August
There
is an exception in NEC2011 regarding the point of
connection. This may not apply, but you could avoid the
supply side. 4500W / 240V = 18.75 x 1.25 = 23.4A, well
under the 120% rule. reference 705.12(D)(2)
-----
Original Message -----
Sent:
Wednesday, February 27, 2013 2:15 PM
Subject:
[RE-wrenches] Conductor Sizing for Supply Side
Connection
Wrenches,
On an upcoming job we have a Xantrex
XW4548 interconnecting with a 200A service, and I’d very
much appreciate some advice if y’all are willing.
Since the inverter output OCPD is
required to be 60A we are looking at a supply side
connection, and I have two questions:
1. Before the
point of interconnection the inverter output circuit will
first pass through the XW Power Distribution Panel and
inverter bypass, which is essentially a 60A breaker. The
service disconnect for the supply side connection will also
be fused at 60A. Does the 120% rule apply to the conductor
between these two OCPDs? Or since this is a supply side
connection in accordance with 690.64(A), 690.64(B)(2) will
not apply? [this AHJ is on the 2008 NEC]
2. Can anyone
recommend a reliable insulation piercing tap connector? Or
would you recommend something else entirely for a
residential supply side connection?
Thanks in advance,
Garrison
847-677-0950
Solar Service Inc.
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