Sometimes utilities will set a max too- here in Florida the
investor-owned utilities have a rule that you take (d...@stc) x 0.85 to
get the "AC equivalent" size of the array. That size then can't exceed
90% of the service rating. Not sure if this is an issue in other states.
Scott McCalmont wrote:
Going all the way up to the rating of the service might not be such a
good idea. The utility may use smaller wires for the service drop than
you would expect based on the ampacity tables in the NEC. Considering
the example of a 400 A service:
- PG&E (local utility) requires 350 kcmil Aluminum conductors.
- Table 310.17 rates 350 kcmil Aluminum for 395 amps before temperature
correction.
With load diversity the smaller wires will be fine, but the output of a
PV system is continuous. Running the output of a system sized at 400
amps through the wires on a hot summer day could overload them.
So... it depends.
Scott
Scott McCalmont, P.E.
McCalmont Engineering
San Jose, CA
(408) 204-0318
On Thu, Mar 4, 2010 at 3:02 PM, Michael Kelly <m...@solarflair.com
<mailto:m...@solarflair.com>> wrote:
Kirpal,
That was always my interpretation as well. So in the case of a 400A
service, I can backfeed 400A when utilizing a supply side
connection. Others have thoughts on this?
- Mike
--
Michael Kelly
Project Manager / Project Engineer
NABCEP Certified Solar PV Installer ™
SolarFlair Energy, Inc.
11 Mayhew Street
Framingham, MA 01702
Direct Mobile: 617-899-9840
Main Phone: 508-293-4293
Main Fax: 508-293-4003
m...@solarflair.com <mailto:m...@solarflair.com>
On Thu, Mar 4, 2010 at 4:16 PM, Kirpal Khalsa <solarwo...@gmail.com
<mailto:solarwo...@gmail.com>> wrote:
Mike.....i may be wrong....but I think i am right....you are
limited by the wire size feeding the supply and/or the
transformer size which supplies the service.....depending on the
physical location of the tap you may be limited by the enclosure
and the enclosure ratings as well
would love to hear any other ideas...
Cheers,
--
Sunny Regards,
Kirpal Khalsa
NABCEP Certified Solar PV Installer
Renewable Energy Systems
www.oregonsolarworks.com <http://www.oregonsolarworks.com/>
541-218-0201 m
541-592-3958 o
On Thu, Mar 4, 2010 at 12:50 PM, Michael Kelly
<m...@solarflair.com <mailto:m...@solarflair.com>> wrote:
Hi All,
Next to grounding, I find the calculation of the maximum
amount of backfeed current allowed in a supply side
connection to be the most vague issue in Article 690. Let's
assume we have a 400A, 480/277 service in a commercial
building, a 400A main service disconnect, and the
jurisdiction is under NEC 2008. What is the maximum
backfeed current allowed in a supply side connection? The
only place the code points you to is 230.82(6), which is no
help, or to Article 705, which is no help either. I know
that in the draft version of NEC 2011, there is
an expansion of 705.12(A) which states "* *Supply Side. An
electric power production source shall be permitted to be
connected to the supply side of the service disconnecting
means as permitted in 230.82(6). The sum of the ratings of
all overcurrent devices connected to power production
sources shall not exceed the rating of the service." That
is a helpful sentence from the Code, but as it is in draft
form, what do we do under NEC 2008? What have you used as a
maximum backfeed current for supply side connections?
Thanks,
Mike
--
Michael Kelly
Project Manager / Project Engineer
NABCEP Certified Solar PV Installer ™
SolarFlair Energy, Inc.
11 Mayhew Street
Framingham, MA 01702
Direct Mobile: 617-899-9840
Main Phone: 508-293-4293
Main Fax: 508-293-4003
m...@solarflair.com <mailto:m...@solarflair.com>
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
<mailto:RE-wrenches@lists.re-wrenches.org>
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
<http://www.re-wrenches.org/etiquette.htm>
Check out participant bios:
www.members.re-wrenches.org
<http://www.members.re-wrenches.org/>
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
<mailto:RE-wrenches@lists.re-wrenches.org>
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
<http://www.re-wrenches.org/etiquette.htm>
Check out participant bios:
www.members.re-wrenches.org <http://www.members.re-wrenches.org/>
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
<mailto:RE-wrenches@lists.re-wrenches.org>
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
<http://www.re-wrenches.org/etiquette.htm>
Check out participant bios:
www.members.re-wrenches.org <http://www.members.re-wrenches.org>
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options& settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules& etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
