Hi Drake
That breaker internal to the SI might be OK for Europe, but it doesn't
fly here in the US.
Here, you must use an external switch or breaker as a disconnect. You
can use a fuse too if you
want to.
MidNite has just started shipping our SMA/SI E-Panel that uses the 250
amp breaker.
We have been working with SMA on this one. The SMA E-Panel is designed
to integrate battery
based grid tie with AC coupling.
boB
On 4/10/2013 6:52 AM, Drake wrote:
boB,
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?
Thanks,
Drake
At 12:14 AM 4/10/2013, you wrote:
After 100's of thousands of inverters having been shipped in the
last many years
and thousands of inverters broken and shorting the battery terminals,
there has
never been (to our knowledge) one breaker that has not tripped.
The Midnite site lists the AIC rating of all our breakers I believe.
The Carling F series of Magnetic-Hydraulic breakers poop sheet is here...
http://www.carlingtech.com/sites/default/files/documents/F-Series_Details_%26_COS_0.pdf
I guess there isn't a graph of AIC vs. voltage on their F series web
page but we remember
them showing us figures or a graph that says those breakers have an
AIC of more than
100,000 amps at 48 volts. We'll try to find that info or you may be
able to get that
from Carling.
I have, many times, directly connected these breakers across good
L-16 battery strings
to demonstrate the left-hand rule to people where the 4/0 cable jumps
apart or towards each
other when very high current passes through those wires when they are
near each other.
It always trips. Never tried it at anything above a 48V battery
banks IIRC.
Robin would like to mention that anyone that wants to use T-Classc
fuses.... Welcome back to the 1990's
boB
On 4/9/2013 1:23 PM, Ray Walters wrote:
Hey Bob;
Can you share that AIC vs Voltage chart?
Thanks,
R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760
On 4/9/2013 1:46 PM, boB wrote:
Those 250 amp and 175 amp breakers we have used for many many years now
have an AIC of 50,000 amps at 125 volts and if you look at the
curve, at 48 volts
they are around 100,000 amps. I think that this information is on
the label
of the breaker.
How many problems have you had with the Carlings or any other type of
those large breakers ?
boB
On 4/9/2013 10:40 AM, Michael Welch wrote:
If anyone would like an Acrobat version of this article, you can
find it here:
ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf
<ftp://ftp.re-wrenches.org/pub/hp27_pg26_freitas.pdf>
William Dorsett wrote at 07:00 AM 4/9/2013:
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 /Overcurrent Protection for
Battery-Powered Systems /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.
175A ITE breaker with 42,000 AIC "simply tripped...but still
allowed a peak current of 2960 amps
200A Class T Littlefuse "opened promptly with no external signs
of stress...1920 amps peak current"
Christopher's recommendations:
"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.
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.
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.
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."
It won't pull up anymore on HP's article search but probably
Michael has a copy he could post for those interested./
/
Bill Dorsett
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