"Point of Connection" To Tap, or Not to Tap" [RE-wrenches]

[Damian de Caires]

You do not need to size it equal to the service conductors because the
service conductors are sized to the main breaker ampacity which is far
higher than the backfeed ampacity.  You do need to size it to the
backfeed ampacity on the mains at the fused ac disconnect or the mains
of the solar sub panel depending on how you ran it.  You are required to
use a metal conduit with the tap, one suggestion is don't run the tap
conductor through the panel and exit a knockout because unprotected
lines should not be located unprotected next to protected lines.  If you
want to be really clean tap on the outside rather than in the service,
or 
	What I would suggest to the inspector is to install an external
mains and tap the conductors inside the service panel, in which case the
external mains has to rated for the 20% backfeed rule, for example if
you are backfeeding 50amps and it is a 200amp service with a 200amp then
the external mains would need to be a 225 bus with a 200amp main.  Since
the mains at the service limits the load to 200amps; the feeder cable
between the new external disconnect and the service panel would not have
to be resized since it's potential is still only 200amps not 250.  Now
if you are in a territory where you still need an external pv ac
disconnect I would tap in outside (behind the new external mains) and
run into the building.  Why having an external mains is better is now
since it is protected you are exempt from the metal conduit (although
with a picky inspector you probably should anyway), and it is a safer
system since now there are no unprotected conductors in the house.  You
may get issues from the utility for opening up the meter to disconnect
the feeder cables but your options are limited. 
	I think that the inspector is incorrect because 690.64B1 states
either fused disconnect or breaker.  I would email John Wiles because as
I understand it a fused disconnect is connected via a tap and only via a
tap because if it was a breaker then no fused disconnect right?  Ok
ignore what I said above, can you install a couple double switch single
space breakers in the panel to free up space and run into a breaker?  I
would do that first to get the job done and satisfy the inspector and
also send John Wiles an email to clarify the issue and if you could send
me a copy of his reply please do for everyone's files.

-----Original Message-----
From: Bruce Leininger [mailto:bruce.leininger at sbcglobal.net] 
Sent: Friday, September 15, 2006 12:52 AM
To: RE-wrenches at topica.com
Subject: "Point of Connection" To Tap, or Not to Tap" [RE-wrenches]


Hi all.  Has anyone run into Article 690.64 being interpreted as
prohibiting taps to the load side of the main service breaker?  One
particular municipality is saying that, even with a fused AC disconnect,
taps are not allowed because of Item B (1) which says "Each source
interconnection shall be made at a dedicated circuit breaker or fusible
disconnecting means." 

The only issue that occurs to me is the protection of the section of
wire between the tap and the fuse in the AC disconnect.  Would it seem
reasonable to size that section of wire equivalent to the service
conductors?

Has anybody else run into this?  How have you handled it?

The municipality in question suggests tapping on the supply side of the
main breaker, but that seems much less safe.  The current on the wire
between the fused AC disconnect and the tap then only be limited by the
overcurrent protection on the utility transformer, no?

Thanks for you help.

Bruce


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