Posted 20 hours ago

Blue Sea Systems Class T Fuse Blocks

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One of the most important aspects of electrical wiring of photovoltaic systems is fusing. Fuses provide integral protection against overcurrents that could otherwise damage your valuable PV equipment. Furthermore, using an incorrect fuse can be extremely hazardous! Can you point to this standard? I have been trying to look into this recently, but the latest publicly available version of the ABYC E-11 is 2008 when LFP was in its infancy. They do not differentiate OCP based on battery type, only on battery bank size. In this photo we can see the battery bank and the red 2/0 wire feeding the Class-T fuse holder. At a bare minimum you want to be using Class-T fuses as your main bank protection for an LFP bank. Time-delay: A fuse in which the burnout action depends on the time it takes for the overcurrent heat to build up in the fuse and melt the fuse element. DC circuits, All general purpose circuits, Motors, Transformers, Solenoids, Fluorescent lighting, All system components with high in-rush currents

At the same time I know from experience that inverters don’t care if you use an external fuse or not and that Gopower is a reputable mfg and their equipment has internal fusing and will protect itself. And I know that the real use of the ‘catastrophic’ fuse is to protect the wiring. My wiring will be simple and short. 2 gauge battery cable. The battery and the inverter will be close together inside the living space. Skoolie. I’m much inclined to use a 300A MRBF fuse. That might clip my surge limit but I don’t expect to use that much power anyway. Alternatively Blue Sea makes a 400A ANL. That wouldn’t clip my surge and would still protect my wiring.All general purpose circuits, Motors, Transformers, Solenoids, Fluorescent lighting, All system components with high in-rush currents Fast-Acting — Provides fast-acting overload protection to equipment such as variable speed drives, rectifiers and other equipment containing surge-sensitive components. Circuits having relatively low levels of available short circuit current, Industrial and commercial applications having frequent outages where a renewable type fuse is desired

The only unsafe failures we had were off-brand el-cheapo car stereo type ANL fuses. As can be seen here the windows literally exploded out of the fuse when it tripped. I did not have a single unsafe failure of a Cooper Bussmann/Blue Sea Ignition Protected ANL fuse but I only blew about 10 of them. I suppose if you blew 100 you may have an unsafe failure on an LFP bank.. Interrupting rating: Interrupting rating is the current that a fuse, circuit breaker, or other electrical apparatus is able to interrupt without being destroyed or causing an electric arc with unacceptable duration.

Please note:

Still, I would strongly urge Class-T as the bare minimum for LFP bank main over-current protection. Please refer to NEC code Article 240 Overcurrent Protection when sizing the fuses for your application. The lithium jump starter is going to be made as small as possible, sufficient to deliver cold cranking amps. Maybe 600A into 8V for a 12V starter? So that might be 1800A into a short. I doubt it is 10's of thousands, but I haven't worked with lithium. If it could do 10's of thousands, I think a smaller cheaper battery would have been used, still able to turn the car engine over. Current limiting design greatly reduces damage to equipment caused by heating and magnetic effects of short circuit currents.

Current limiting: A current-limiting device is one that reduces the peak let-thru current to a value substantially less than the potential peak current that would occur if the current-limiting device were not used. Fused combination motor controllers to provide IEC Type 2 (“No Damage”) motor branch circuit short-circuit and ground fault protection, Motor control centers, Transformer protection, Protection for UL Listed series rated molded case circuit breaker panels, General purpose circuits — mains, feeders and branch circuits — especially when space is limitedThis last point is where a class T fuse shines. A class T fuse has the ability to reliably break a extremely high ampere current. Much higher than MRBF or ANL fuses. It is my understanding that this is much more important with lithium batteries because of the low resistance, a lithium battery can pour so much current into a short. With lead acid battery banks, ANL, MRBF, and Class T fuses are all permitted for main battery protection by the ABYC (US marine code), but with lithium's much greater ability to supply current, a fuse with a very high AIC becomes much more useful (or even mandatory--i'm not sure about this). Remember an ANL IP rated fuse has an AIC of 6000A and a Class-T non IP fuse has a 20,000A interrupt rating.. If you have a gasoline powered vessel, which requires ignition protected devices, consider this when engineering the over current protection for your LFP system..

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