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>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
303 505-8760On 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
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
Christophers 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 wont pull up anymore on HPs article
search but probably Michael has a copy he could post for those interested.
Bill Dorsett
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