Overcurrent Protection


Batteries can produce vast amounts of current all at once if there is a short or fault in a circuit. This rapid discharge can heat wires or other components to critically high temperatures, melting insulation and / or starting fires. To protect against this possibility, fuses or breakers are installed into systems to disconnect a circuit in the event of such a fault. They act as a weak - link in the circuit which will trip or open before any damage or fire hazard occurs. each circuit should be protected in this way, with a fuse or breaker rated for less current than the wires can safely handle. For example, a lighting circuit with 15 amps of lights on 12 gauge romex (good for 20 amps) should be protected by a fuse or breaker of no more than 20 amps, yet more than 15 amps, the expected load. PV modules should also be protected - not from the power they produce, but from the battery or to help protect against lightning strikes. Any externally mounted component (windmill, solar panel, hydro plant, genset, etc.) should also be protected with a lightning / surge suppressor for maximum safety and protection. DC circuits should be protected with appropriate DC rated devices, And AC circuits should be protected with equipment designed for that application. The DC rated devices are generally heavier duty and more expensive than their AC counterparts. If you are installing your own system, we suggest that you obtain a copy of the National Electric Code, and work with your local electrical inspector . We offer and suggest the publication, “PV Power Systems and the N.E.C. Suggested Practices,” free to anyone who is interested. (postage not included)


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