[RE-wrenches] Conductor Sizing for Supply Side Connection

[August Goers]

Hi Garrison,



In my opinion you only need to size the conductors to the overcurrent
protection. Bill Brooks addressed a similar question of mine a few months
ago - I've attached the email here. If you do a node analysis (ie see what
would happen under both normal operation and fault conditions at any given
point) you'll see that the current at any given point along the wire path
will never exceed the breaker ratings on either side (or the higher of the
two if they're different). It is a different story from what the 120% rule
is addressing - in that case the current feeding into a busbar has the
potential of being supplied by both the main breaker and the solar breaker
thus potentially exceeding the bus capacity.



I've used insulation piercing connectors from Burndy and Ilso with good
results. Ilsco is called KUP-L-TAP and part number IPC-4/0-2/0 is a common
one. You'll need to find the part number that best matches your wire size.



It's a bit of a separate issue, but I've found that many jurisdictions are
very critical of supply side connections and can start to ask questions
about whether the whole setup is listed for the purpose. It is nearly
impossible to get the manufacturer to list the entire service and line tap
in my experience. You might want to look into that if you think your
jurisdiction might have similar concerns.



Good luck!



Best,



August





August Goers



Luminalt Energy Corporation

1320 Potrero Avenue

San Francisco, CA 94110

m: 415.559.1525

o: 415.641.4000

august at luminalt.com





*From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Garrison Riegel
*Sent:* Wednesday, February 27, 2013 1:15 PM
*To:* 'RE-wrenches'
*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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