We installed 2 of the original SI4248s back in 2006. The installation manual specifically noted that the units had a "Built in DC disconnect" though and not a circuit breaker. There is no mention of interrupt current.
Instructions also said to "Ensure that an approved DC disconnect and over-current protection is installed between the batteries and inverter." Both have worked flawlessly since then except that in 2011 one of the "disconnects" developed a bad connection and arced when turning the unit on. Jim Duncan North Texas Renewable Energy Inc www.ntrei.com <http://www.ntrei.com/> NABCEP PV 031310-57 TECL-27398 nt...@1scom.net 817.917.0527 NABCEP Logo From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Drake Sent: Wednesday, April 10, 2013 7:52 AM To: RE-wrenches Subject: Re: [RE-wrenches] Fuse sizing in battery circuits 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_%2 6_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 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 _______________________________________________ List sponsored by Home Power magazine List Address: <mailto:RE-wrenches@lists.re-wrenches.org> RE-wrenches@lists.re-wrenches.org Change email address & settings: <http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: <http://www.re-wrenches.org/etiquette.htm> www.re-wrenches.org/etiquette.htm Check out participant bios: <http://www.members.re-wrenches.org> www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: <mailto:RE-wrenches@lists.re-wrenches.org> RE-wrenches@lists.re-wrenches.org Change email address & settings: <http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: <http://www.re-wrenches.org/etiquette.htm> www.re-wrenches.org/etiquette.htm Check out participant bios: <http://www.members.re-wrenches.org> www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Change email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org <http://www.members.re-wrenches.org/>
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