Hi, I'm hoping to get some advice on how to provide adequate fuse protection for this system I am developing. It is based on the Electrodacus SBMS0, which is why the solar array is weird - no series strings. I understand the need to protect the wiring from overcurrent caused by a short or other defect. The current sources are the solar array, which should max out at about 130A, and the battery, which could provide thousands of amps in a worst case scenario.
I gather that a Class T fuse is necessary to reliably disconnect the battery. Maximum current drawn by the 3500W inverter would be at full load when the battery is at lowest voltage, right? So 3500/20 = 175A. Would a 200A fuse provide enough headroom? The 50mm2 cable is rated to 246A so I could go to 225A for that fuse.
The wiring from the solar array is where I am confused. The individual wires (6mm2, rated to 70A) from the parallel pairs of panel would see about 22A in freakish conditions from solar input. If I shorted a pair out on a sharp bit of roofing, they would see the full force of the battery until the DSSR20 burned out. That's a pretty unlikely scenario and not outrageously dangerous. I have sketched some generic breakers which I think would be much more convenient to use as switches than fuses would be. Does that make sense?
The 35mm2 cables from battery to the charge bus need protection only from solar output, assuming my Class T is already in the circuit. This means I could use a less costly fuse type to protect these cables, right?
The Electrodacus designer does not want a fuse between the battery and the shunts. What about I put the Class T on the negative battery terminal and the other fuse (ANL maybe?) on one of the 35mm2 cables next to either charge bus?
I'd really appreciate an input that will help me avoid burning my shed down.
Leon
I gather that a Class T fuse is necessary to reliably disconnect the battery. Maximum current drawn by the 3500W inverter would be at full load when the battery is at lowest voltage, right? So 3500/20 = 175A. Would a 200A fuse provide enough headroom? The 50mm2 cable is rated to 246A so I could go to 225A for that fuse.
The wiring from the solar array is where I am confused. The individual wires (6mm2, rated to 70A) from the parallel pairs of panel would see about 22A in freakish conditions from solar input. If I shorted a pair out on a sharp bit of roofing, they would see the full force of the battery until the DSSR20 burned out. That's a pretty unlikely scenario and not outrageously dangerous. I have sketched some generic breakers which I think would be much more convenient to use as switches than fuses would be. Does that make sense?
The 35mm2 cables from battery to the charge bus need protection only from solar output, assuming my Class T is already in the circuit. This means I could use a less costly fuse type to protect these cables, right?
The Electrodacus designer does not want a fuse between the battery and the shunts. What about I put the Class T on the negative battery terminal and the other fuse (ANL maybe?) on one of the 35mm2 cables next to either charge bus?
I'd really appreciate an input that will help me avoid burning my shed down.
Leon