Another key is to remember that this discussion also applies to the
conductor between the main panel and subpanel. In a large PV system,
this could result in a pretty large wire between the two panels, and a
significant cost that is often overlooked. In some cases it makes sense
to locate the subpa
Jason,
I think, going back to the diagram in the article, the feeder breaker is
rated at 80A, the feeder conductors are rated at 80A, and the subpanel is
rated at 80A, assuming that there are no loads connected in the subpanel.
Even if there were up to 100A of loads in the subpanel, you would not
Is a monitoring system installed in the Load Center to measure the
cumulative kWh's of the inverter's considered a load?
The type of monitoring device I am talking about has CT's that go around the
conductors and the Voltage ref is taken by attaching conductors to each
phase, the Neutral and the
Hmmm. That's not the way I understood it. I could be wrong.
690(B)(2): The sum of the ampere ratings of overcurrent devices in
circuits supplying power to a busbar or conductor shall not exceed 120
percent of the rating of the busbar or conductor. In systems with
panelboards connected in series
To echo the wording in Kent's response, John Wiles has always advised that
it doesn't matter if there are currently loads connected to the
panel/conductors; if the panel/conductors are capable of having additional
loads connected to it, you need to apply 609.64(B)(2). I have had luck with
AHJ appro
Jason,
Now you are opening up a can of worms.
It's bad enough that 705.12(D) doesn't say anything about a panel that
can't (or shouldn't, or won't) have anything connected but interactive
inverters. But when that is the case, a bus rating of 100% of the
source circuits should apply. For PV s
Al,
I would say that yes the meter is a load and this goes to show the relative
inadequacy of the vocabulary we are using in the discussion. In the example
we have been using with the 80A breaker, wire and sub panel, you could have
up to 80A of loads installed in the sub and still not create an o
Al,
How about a 15-amp single-pole breaker for power line carrier
communications equipment to talk to the inverters?
Technically, I think either way they are loads and that changes
everything. But in my opinion they are minor and should be allowed
without considering the sum of all sources.
K
This is diagram is based on a 3-phase 208 V service, as clarified in the
text accompanying the diagrams. There is a mistake of sorts, however. The
authors¹ original manuscript called out a ³generic² 7500W inverter connected
to 50A, 2-P breaker. We then added more detail, calling out a Fronius 7500W
I am wondering if anyone has had a NABCEP stamp made to stamp plans. I have a
city agency who is comfortable with the NABCEP certification as a
qualification, but would like to see a stamp. Has anyone out there done this?
Troy
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Wouldn't a fault in that conductor between the main and the sub have a
potential for up to 160A of current? I would think that at noon on a sunny day,
the inverter system could produce 80A from one direction (albeit really only
the max amperage outputs of the inverters) and 80A of grid current f
That is a really good question Brian.
Mostly when thinking about these sizing issues I think about overload
conditions and not so much about short-circuit and ground fault conditions.
So two questions come up:
1 - What does a UL1741 inverter do when it is connected to a line that is
experienc
I concur with Jason and Brian's interpretation of 690.64(B)(2). I think
one of the intents of the code is to ensure that if there is a fault in a
busbar or conductor and the maximum amperage is being delivered to that
fault from all OCPDs supplying it (solar + utility), the busbar or conductor
sh
Here is a 690.64(B)(2) opinion from Wiles that may help.
http://www.fafcosolar.com/download/409/690%2064%28B%29%282%29TECH-1.pdf
It's still my contention that the conductors need to be sized for 150A
in this example, unless an exception is made by the AHJ. If David
Brearley's post about Wiles
Troy - I have not encountered this before but would you mind sharing what
city agency you are refering to? NABCEP is always interested in hearing
about these types of "unconventional" uses of the certification.
For a brighter energy future,
Andrew Truitt
Principal
Truitt Renewable Energy Consul
Agreed:
http://solarprofessional.com/article/?file=SP2_3_pg16_QandA_2&search=
You¹ll notice that none of the more permissive proposals that John mentions
here actually made it into NEC 2011.
On 3/30/11 1:07 PM, "Jason Szumlanski" wrote:
> Here is a 690.64(B)(2) opinion from Wiles that may hel
By this argument, wouldn't it be necessary to check every conductor in the
backfeed path adding potential PV amps to their required ampacity including
the utility conductor from the transformer?
Kris
Legacy Solar, LLC
864 Clam Falls Trail
Frederic, WI 54837
715-653-4295
sol...@legacysolar.com
ww
I hope there are no potential loads between the meter and the
transformer, so no! Technically, if it is a supply side tap, the
evaluation would include the conductor from the meter to the main
distribution panel I believe, but if it is a load side connection it
does not matter because of the main b
Per your question:
> 1 - What does a UL1741 inverter do when it is connected
> to a
line that is experiencing a short-circuit or ground fault?
Presuming a hard short, the voltage in that circuit would be essentially zero,
and a UL1741 compliant inverter would cease producing power in less than
Right, so going totally on the fly at the white board, let's say we have an
inverter with a 45A AC output, it see's the short and pours it's little
heart out at 45A for 0.1 sec before shutting out, delivering 4.5 A-sec of
energy into the fault. Meanwhile we take out a clearing time curve for the
g
Troy,
On Mar 30, 2011, at 10:04 AM, Troy Harvey wrote:
I am wondering if anyone has had a NABCEP stamp made to stamp plans. I have a
city agency who is comfortable with the NABCEP certification as a
qualification, but would like to see a stamp. Has anyone out there done this?
Troy
I'm with And
You're overlooking an important fact.
Grid-tie inverters are current-limited devices. They lack surge capability.
Trip times for various circuit breakers vary depending in part on the overload
as a percentage of the breaker's ratings and the circuit breaker temperature
(for thermal breakers).
I hate to mention the evil insurance industry. However, a stamp implies some
professional liability insurance to me.
There are other professional membership organizations (RESNET) that have
developed a tailored professional liability insurance package for its
credentialed members with a preferred
I recently used a Hubbell Killark product for rigid/IMC and was not happy with
how the threads of the coupling engaged in factory conduit threads.
Crousehinds XJG-EMT series is intended for EMT. And is described as being used
indoors or outdoors. The EMT couplings mostly seem to be compressio
Andrew and Troy,
While I can't speak for NABCEP, I would expect that NABCEP should be very
opposed to this type of use of their logo. NABCEP does not certify the work
that a NABCEP certificant does. They only certify that the installer has met
the obligations for certification. There is a HUGE
Back in '06 I got a nifty roll of stickers that I think were meant to be put
inverters. But we put so much (doubtless important) signage on our systems,
I stopped using them. Maybe they might be used on plans.
- Peter
Peter T. Parrish, Ph.D.,
Hi everyone,
I think that Bill has summed it up very well. Stamps on plans
generally imply the review of a duly recognized engineer. NABCEP
Certification is not an equivalency to being a PE.
I must say that I am pleased to hear the jurisdiction
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