Glenn,
While the installation may not claim exact compliance with the current NEC
(debatable), you can easily show that the TL inverter is much safer than the
older 1800U. The TL has arc-fault detection and much better ground-fault
detection. Conduit is not the answer since it breaks several
Jarmo,
The sun’s geometry is not nearly that simple. To understand the impact of
north-facing arrays, you have to perform a simulation. PV:WATTS does this just
fine and it is easy to show that a 18-degreed North-facing tilt produces 75% of
a perfect 30-degree south-facing array. Far more than
Jarmo,
Unfortunately, simple is wrong in this case—and detrimental to the PV industry
that needs all the roof real estate it can find.
Bill.
Bill Brooks, PE
Principal
Brooks Engineering
From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf
Of jarmo.venalai.
Larry and Peter,
You are too old-school to think outside the box. It’s not about direct
sunlight—it’s all about kWh/m^2/day and those numbers don’t lie. Your analysis
is not correct and this is why simple analyses will always give you a wrong
answer.
North-facing arrays have been financial
Jarmo,
Your intent was laudable, but simple trigonometry just flat out fails with the
complexity of solar geometry. PVWatts is so easy to use that anyone, without
any knowledge of trigonometry, can use it with far more accurate results. Take
advantage of nice, free software that your tax doll
Ray,
Do you have a massive battery bank and 3, 8kW inverters inside the house? Is
this in a garage or power shed. If it is a power shed, then 690.12 is not
intended to relate to the power shed. That will be clarified in the 2017
NEC.
The area for discussion is what constitutes the length of batte
Brian,
I don’t know that I have a lot of good news for you. I have looked into this
and I really don’t see a good way out of making some pretty conservative
assumptions. You can read what I wrote in my IAEI article on Support of Exposed
Cable earlier this year. I get into ampacity briefly tho
Craig,
This one is easy to misinterpret. You missed the words “live parts”. This has
been removed from the 2017 NEC because it is actually referring to load
circuits being fed directly by a PV system on the dc side. All references to
loads and batteries are being removed from 690.
This is
William,
I’m shocked and offended (a tiny bit) that you would prejudice yourself to not
agree with me ;-).
First of all I have been heavily involved in the revising of the language in
690.31(A) to make it clear that we cannot walk up and touch cables operating at
600V. The term guarded is
William,
You can always quote me to an AHJ, as long as I actually said it or wrote it.
I have been accused of saying all kinds of things that I never said—people just
misunderstood what I said and “quoted” me incorrectly.
All the best—and stay safe. Always tragic to hear of electrocutions
Jay,
I always try to carry on meters. This includes I-V curve tracers and such. TSA
will often ask you to turn them on.
Bill.
-Original Message-
From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf
Of jay
Sent: Monday, November 09, 2015 3:50 PM
To: RE-wrenches
William,
It appears that most (not all) of the damage you show on your website is due to
incidental contact of bare copper with the aluminum. Also, dripping from bare
copper to aluminum is a problem particularly in a marine environment. Lastly,
the Coast Guard has been using unframed modules
Dan,
I concur with your basic assessment. After listening to an Aquion presentation,
and reviewing the operating curves, this battery has a very narrow application.
Most off-grid houses these days have significant surge loads. That is why we
spend so much time and effort making sure our
All,
Here is the new language that has been approved for the 2017 NEC (more
authoritative than JW).
705.12(B)(3)(d)
(d) A connection at either end, but not both ends, of a center-fed panelboard
in dwellings shall be permitted where the sum of 125 percent of the power
source(s) output
Phil,
I think you already understand how to apply the “120% rule.” All this is saying
is that the breaker can go at either end of a center-fed panel for dwellings.
Do you understand now?
To summarize—a 200A center-fed panel would allow a 40-amp PV breaker to be
installed at either end to
Chris,
While John’s article may seem like a logical interpretation of the 2014 NEC, if
you lived in the western half of the United States where these panels are
common, you would have a very different view of his choice of articles.
His article sites a technicality that is not a safety co
Howie,
To clarify what the 2017 NEC states, it allows for either end of the bus. There
is some value to having loads in between the PV breaker and the main breaker.
Also, by putting the PV breaker as far away from the main as possible, the heat
of both breakers are likely to affect each othe
Ray,
I guess I have to step in after that acknowledgement. PV system circuit is a
self-defined term and therefore cannot be defined unless you are going to
develop a meaning that is different from the self-definition. It means ANY
circuit in a PV system. This includes battery and stand-alone circu
Chris,
Just to add a fine point of clarification, 690.31(G)(4) requires that the
"warning" sign on conduit be Reflective, Capitalized, with white lettering
on Red background. This intentionally does not match the ANSI color schemes
for signs. The NEC overrules ANSI in this case.
If AHJs req
Chris,
Where sign requirements (whether in NEC, IBC, IFC, IRC, etc) have specific
requirements for specific signs that may not agree with the basic ANSI
rules, the code requirement applies. Where no color requirement accompanies
the sign, then the ANSI color designations would be most appropria
Dana,
Reaching back into my brain archives, having done a few projects with these
modules, I know that many, if not all, of these modules were rated for a
maximum system voltage of 48-volts. They can’t be used on higher voltage PV
arrays.
This was a budget version of their standard produ
All,
The 2011 NEC reference for stand-alone systems is 705.12(D)(2) Exception:
Exception: Where the photovoltaic system has an energy storage device to allow
stand-alone operation of loads, the value used in the calculation of bus or
conductor loading shall be 125 percent of the rated uti
Steven,
Although you are correct that OSHA certifies NRTLs for specific test standards,
I have not run into jurisdictions in California that reject products listed to
UL standards by ETL, TUV, and CSA. There have been specific cases where the
County and City of LA have questioned various pro
Eric,
Your reasoning sounds logical, but it is missing the point. Transformers have
to be protected by overcurrent devices, similar to wire. Inverters are current
limited devices so they only have to be able to withstand a certain size
circuit breaker. The current from the inverter is consider
Eric,
No worries on the education side. I’ve been educating for nearly 30 years in
this field. I’m learning new stuff every day so I expect others to have the
same commitment to learning. I’m glad to see that you do.
One personal frustration with the listing label on inverters is that the
William,
I’m not sure you meant to imply this, but carports and groundmounts do not need
any RS equipment unless you were to bring the dc conductors into a building,
which would not be smart.
The 2017 NEC allows connectors to be used as isolation devices for equipment as
long as the circ
William,
I was also surprised to see SMA go down this road (ala Fronius IG). I can’t
speak to why they did this. I’m installing my first 40 series right now.
I have never supported covering the array as a viable method of removing
voltage. It is far safer to unplug the strings on the roof
Jay,
You need to provide more information. The 2014 NEC is a significant improvement
in the language related to single-phase inverters on a 3-phase service. To read
it any other way shows a very large misunderstanding of the language.
It should be much better on the 2014 NEC, not worse. Where
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