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Is it possible that not grounding the DC on an inverter could be code
compliant? In the past, we were always required to install
grounding electrode conductors to the DC negative, as required for
grounding Direct Current systems (250 VIII). <br><br>
Maybe grounding can be eliminated in a purely AC coupled system due to
the fact that the system is not supplying premise wiring. Maybe the DC
can be considered as an integral part of the system supplying the AC.
<br><br>
The rules for grounding DC are stated below.<br><br>
250.162 Direct current Circuits and Systems to Be Grounded<br>
(A) Two-Wire, Direct-Current Systems. A 2-wire, dc system supplying
premises wiring and operating at greater than 50 volts but not greater
than 300 volts shall be grounded.<br>
Exception No. 1: A system equipped with a ground detector and
supplying only industrial equipment in limited areas shall not be
required to be grounded.<br>
Exception No. 2: A rectifier-derived dc system supplied from an ac
system complying with 250.20 shall not be required to be grounded.<br>
Exception No. 3: Direct-current fire alarm circuits having a
maximum current of 0.030 ampere as specified in Article 760, Part III,
shall not be required to be grounded.<br><br>
In a Sunny Island system there is no charge control, nothing else in the
DC besides the battery and battery cables. Does not grounding the
negative really meet code requirements in the US ? Are the inverter
cables not considered to be premise wiring?<br><br>
Thanks,<br><br>
Drake <br><br>
<br>
At 03:56 PM 4/10/2013, you wrote:<br>
<blockquote type=cite class=cite cite="">Content-Class:
urn:content-classes:message<br>
Content-Language: en-US<br>
Content-Type: multipart/alternative;<br>
<x-tab> </x-tab>
boundary="_000_B448FC9E37458B469E77EA0BB954AD4702BD99AC6Emailbox01_"<br>
<br>
August:<br>
<br>
The SI can run with an ungrounded battery or a grounded battery.<br>
With the internal breaker it is set up for a negative ground
battery.<br>
I believe the manual says ground at the battery terminal.<br>
If you chose to go ungrounded you will need to have an OCPD in both
battery + and battery – (all ungrounded conductors).<br>
<br>
I am pretty sure the SI is not internally bonded to ground.<br>
This is normal in the rest of the world.<br>
Mine are running with an ungrounded battery and there isolation between
battery and ground.<br>
<br>
Best Regards,<br>
<br>
John Berdner<br>
General Manager, North America<br>
<br>
SolarEdge Technologies, Inc.<br>
3347 Gateway Boulevard, Fremont CA 94538 USA <b><i>(*Please note of
our new address.)</i></b><br>
T: 510.498.3200, X 747<br>
M: 530.277.4894 <br>
<br>
<b>From:</b> re-wrenches-bounces@lists.re-wrenches.org
[<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" eudora="autourl">
mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of
</b>August Goers<br>
<b>Sent:</b> Wednesday, April 10, 2013 9:45 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Fuse sizing in battery circuits<br>
<br>
Hi All -<br>
<br>
As a slightly separate topic, should we fuse both the positive and
negative battery lines with an SMA Sunny Island? I believe that the
negative is grounded so should not be fused but I've heard conflicting
stories from tech support.<br>
<br>
Thanks,<br>
<br>
August<br>
<br>
<b>From:</b>
<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org">
re-wrenches-bounces@lists.re-wrenches.org</a>
[<a href="mailto:re-wrenches-bounces@lists.re-wrenches.org" eudora="autourl">
mailto:re-wrenches-bounces@lists.re-wrenches.org</a>] <b>On Behalf Of
</b>Drake<br>
<b>Sent:</b> Wednesday, April 10, 2013 5:52 AM<br>
<b>To:</b> RE-wrenches<br>
<b>Subject:</b> Re: [RE-wrenches] Fuse sizing in battery circuits<br>
<br>
boB,<br><br>
SMA does recommend protecting Sunny Islands with a fuse on the battery,
even though the breakers on the units are rated for 10,000 Amps.
Are the SI breakers inferior others you have mentioned? <br><br>
Thanks,<br><br>
Drake<br><br>
<br><br>
At 12:14 AM 4/10/2013, you wrote:<br><br>
After 100's of thousands of inverters having been shipped in the
last many years<br>
and thousands of inverters broken and shorting the battery terminals,
there has<br>
never been (to our knowledge) one breaker that has not tripped.<br><br>
The Midnite site lists the AIC rating of all our breakers I
believe.<br><br>
The Carling F series of Magnetic-Hydraulic breakers poop sheet is
here...<br><br>
<a href="http://www.carlingtech.com/sites/default/files/documents/F-Series_Details_%26_COS_0.pdf">
http://www.carlingtech.com/sites/default/files/documents/F-Series_Details_%26_COS_0.pdf</a>
<br><br>
I guess there isn't a graph of AIC vs. voltage on their F series web page
but we remember<br>
them showing us figures or a graph that says those breakers have an AIC
of more than<br>
100,000 amps at 48 volts. We'll try to find that info or you may be
able to get that<br>
from Carling.<br><br>
I have, many times, directly connected these breakers across good L-16
battery strings<br>
to demonstrate the left-hand rule to people where the 4/0 cable jumps
apart or towards each<br>
other when very high current passes through those wires when they are
near each other.<br><br>
It always trips. Never tried it at anything above a 48V battery
banks IIRC.<br><br>
Robin would like to mention that anyone that wants to use T-Classc
fuses.... Welcome back to the 1990's<br><br>
boB<br><br>
<br>
On 4/9/2013 1:23 PM, Ray Walters wrote:<br>
Hey Bob;<br><br>
Can you share that AIC vs Voltage chart?<br><br>
Thanks,<br><br>
<pre>R.Ray Walters</pre><font face="Courier New, Courier"></font><br>
<pre>CTO, Solarray,
Inc</pre><font face="Courier New, Courier"></font><br>
<pre>Nabcep Certified PV Installer,
</pre><font face="Courier New, Courier"></font><br>
<pre>Licensed Master
Electrician</pre><font face="Courier New, Courier"></font><br>
<pre>Solar Design
Engineer</pre><font face="Courier New, Courier"></font><br>
<pre>303 505-8760</pre><font face="Courier New, Courier"></font>On
4/9/2013 1:46 PM, boB wrote:<br><br>
Those 250 amp and 175 amp breakers we have used for many many years
now<br>
have an AIC of 50,000 amps at 125 volts and if you look at the curve, at
48 volts<br>
they are around 100,000 amps. I think that this information is on
the label<br>
of the breaker.<br><br>
How many problems have you had with the Carlings or any other type
of<br>
those large breakers ?<br><br>
boB<br><br>
<br>
On 4/9/2013 10:40 AM, Michael Welch wrote:<br>
If anyone would like an Acrobat version of this article, you can find it
here:<br><br>
<a href="ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf">
ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf</a><br><br>
William Dorsett wrote at 07:00 AM 4/9/2013:<br>
<br>
This topic comes up often enough that we ought to mention a yellowed
article in Home Power, (1992 Issue 27, pg 26). Christopher Freitas wrote
<i>Overcurrent Protection for Battery-Powered Systems </i>where he
describes experiments he did back when he was with Ananda. He put a 2000
A Big Switch to initiate a short (4/0 cable) between the terminals on a
set of four golf cart batteries (2 strings @ 12V). In series, he put in a
500A Shunt so he could measure current passing and various fuses and
breakers. “For comparison, we decided to directly short the battery…the
meter read 6960 amps peak current (three seconds) …during each test the
4/0 cable lifted off the ground 4 inches into the air by the forces
generated by the extremely high current..” They videoed the 250 A ANN
buss fuses arc and smoke; the 200A Heinemann Series AM breakers
(paralleled ones that maybe Roy mentioned) went 3 seconds without
breaking and the video showed a flash and blue smoke. <br>
175A ITE breaker with 42,000 AIC “simply tripped…but still allowed a peak
current of 2960 amps<br>
200A Class T Littlefuse “opened promptly with no external signs of
stress…1920 amps peak current”<br>
Christopher’s recommendations: <br>
“Every AE system must have overcurrent protection able to interrupt the
maximum current available from the batteries. For most systems, the main
protection should use current limiting high AIC fuses, such as a Class T
or Class R. A disconnect switch which allows the fuse to be safely
changed should be included. A lower cost alternative is to mount the fuse
in a fuse holder without a disconnect. Although the fuse would always be
electrically hot, it normally would not be changed during the life
of the system. The fuse holder should be mounted outside the battery
enclosure. Fuses should not be bolted directly onto the battery terminal,
as they are not designed to handle the physical stresses that can occur
without the protection of a fuse holder.<br>
<br>
Fuses which have exposed elements, such as ANN fuses, should not be used
because they are not current limiting and have only 2500 amps AIC. They
also may be a significant hazard when installed near batteries. <br>
<br>
High AIC breakers, like the Heinemann Series CF (25,000 Amps AIC @ 65VDC)
can provide overcurrent protection for individual items. They cannot be
used to protect lower AIC breakers. This eliminates their use as a main
disconnect in most systems. <br>
<br>
Low AIC breakers, like the Heinemann Series AM (5000A AIC @65 VDC) or the
Square-D QO (5000A @ 125 VDC) can be used in load distribution centers
and components, but must be protected by a current limiting fuse. Using
low-AIC breakers alone will not provide sufficient protection with a
battery system and may be a significant hazard during short circuit
situations.”<br>
<br>
It won’t pull up anymore on HP’s article search but probably Michael has
a copy he could post for those interested.<i> <br>
</i> <br>
Bill Dorsett<br>
<br><br>
<br><br>
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