We've transitioned from using supply-side taps to using Feeder taps re:
705.12(B) almost exclusively.
The advantages are numerous - and you just added one more - not needing
line side listing on your tap hardware.
One of the most dangerous things I see looming in the present code is
the fact that supply side taps can be safe for backfeeding up to 160
Amps of PV on a standard 200 Amps service IF you are only grid-tie and
the current is canceling incoming current.
But as soon as you add hybrid inverters and batteries. Now you are
adding significant battery charging amperage to the NEC 220 load calcs
that the service entrance connectors are based on.. Given that many
residences utilized the downsize table for service entrance conductors
you can quickly end up with a situation where your supply side tap is
overloading your service entrance conductors if pulling the inverters
full capability for battery charging and adding that to your normal
house loads.
Feeder taps take care of this vulnerability in the present code. By
having a main 200 Amp breaker on both sides of the tap as per 705.122 B
- all conductors are protected for both the increased loads due to
battery charging as well as being able to still use the full 160 Amps
available for backfeed. And you don't have to shut down the utility to
install.
Now you also add not needing to list your taps for supply side and you
can use the venerable ILscos again . . .
Hope that helps!
Best,
Jeff
Brian Mehalic via RE-wrenches <mailto:re-wrenches@lists.re-wrenches.org>
February 1, 2023 at 7:18 PM
The requirements for power distribution blocks (PDB) to be marked
“*suitable for use on the line side*…” when installed connected in
that manner in wireways (Art. 376) and pull/junction boxes (Art. 314)
have been in the NEC® for quite a few cycles.
It looks like the additions to 230.46 in the 2020 NEC® (PDBs and
splices/pressure connectors connected to service conductors must be
marked “suitable for use…”) coincided with this explicit requirement
being removed from 314 (though it remains in 376); this makes sense -
if you’re using a PDB on the line side, well you’re connecting to some
type of service conductors, so why not cover it in Art. 230 (maybe
it’ll also be removed from 376 in 2026).
UL 1953 allows for PDBs (UL product code QPQS) to be listed for
connection on the line side, load side, or both, with those that can
connect on the line side having the marking mentioned above. Note that
many have an SCCR of 10 kA unless combined with
the manufacturer-specified fuse type and size (or smaller), and have
minimum enclosure sizes that must be followed as well. I have had a
difficult time finding PDBs that are marked for use on the line side
while just using the internet (and have been too lazy to pick up the
phone thus far...plus it doesn't help that all PDBs have a line and
load side of the device regardless of whether or not they are being
connected on the line or load side of the service!).
Of course many folks are not going to want to use PDBs due to
re-routing conductors to them (if even possible) and having to shut
down the utility supply to install them. Enter pressure connectors,
and the seemingly industry-fave insulation-piercing style;
unfortunately I'm not aware of any that are available *yet* with the
proper listing and markings as required by 230.46.
A colleague that works for a large electrical product manufacturer
passed this along:
/“No test existed for qualifying single polarity connectors suitable
for line side use when this was added to the 2020 code with the
January 1, 2023 date for enforcement. A strategy and test procedure
needed to be developed and adopted by the UL CSDS working group. Not
a speedy process. Long story short, after developing a strategy,
public comment period and voting the *standard wasn’t published until
August of last year.* On average the testing requirements take about
90 days. To further complicate matters, I was recently told that UL
is still developing the submittal process.
I know that there are a lot of companies currently testing products
but until the UL submittal process catches up, no one will be
official. The *UL product code is ZMWW*; as companies become
qualified they should show up in the ZMWW search. As of today, no one
is listed. This leaves power distribution blocks as the lone
connector product rated for line side use. I know that Bussmann has
some PDBs rated for line side use."
So this begs the question of whether or not NEC® 90.4(D) can be
invoked (new products not yet available at the time the Code is
adopted...); PDBs already exist, so no dice there, and it is likely
that since they exist, an argument using 90.4(D) in regards to
pressure connectors/splices will fall on deaf ears because, well, use
PDBs."/
Ugh.
Brian Mehalic
NABCEP Certified Solar PV Installation Professional™ R031508-59
National Electrical Code® CMP-4 Member
(520) 204-6639
Solar Energy International
http://www.solarenergy.org
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Jason Szumlanski via RE-wrenches
<mailto:re-wrenches@lists.re-wrenches.org>
February 1, 2023 at 6:25 PM
As someone who does 75%+ supply-side interconnections, this kind of
terrifies me. We have another year of NEC 2017 here, so I have time to
prepare, but I'm watching this closely.
Meter disconnects/reconnects here are difficult due to the lack of
good utility company cooperation and the requirement for an inspection
prior to reconnection, which leaves homeowners without power for many
hours at times. Otherwise, I would just pop in a 200A main disconnect
between the meter and main distribution panel and do a feeder tap for
the inverter output between the new service disconnect and the
existing distribution equipment. Unfortunately, that usually means
bringing grounding electrodes and conductors up to current standards,
but that's how we would be forced to comply if this splice/tap rule
comes into effect here and there are no suitable products available.
Side note: 200A 2-pole fusible disconnects are all but impossible to
get here. Even 200A main breaker enclosures are very hard to find.
Hurricane Ian didn't help that with thousands of people who had their
service equipment under water... It has been a challenge.
Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
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August Goers via RE-wrenches <mailto:re-wrenches@lists.re-wrenches.org>
January 31, 2023 at 7:56 PM
Hi Wrenches -
Occasionally we will do supply side connection for our PV systems. As
of 1/1/2023 in CA, we follow the 2020 NEC 705.11 Supply-Side Source
Connections section. Recently, an inspector asked us to comply with
the following:
When we reached out to one supplier of insulation piercing connectors
(ILSCO), they responded: "We are still in testing, I just checked and
from what I see there are no products listed for this new requirement
yet by any manufacturer."
Has anyone bumped into this before and/or have any proposed solutions?
Best, August
Luminalt
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