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Old 07-23-2010, 04:19 PM
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DaveInDenver DaveInDenver is offline
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Join Date: Jun 2006
Location: Larimer County
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If you think you'll use 30A on each of the 6 fuses, then you need about 4AWG, maybe 2AWG, for 180 amps. But that's unrealistic, you should add up what the maximum sustained power you'll need and size the feeding fuse and wiring for that. Then you size the individual fuses based on the size of the branch wiring required for the load.

So say you have 55W fog lights, a 120W compressor, 65W radio and 35W aux lights. That's a total of 275W and at 12V that means you need to feed the block with 23 amps. Give yourself some head room and feed it for 40A, which is about 10AWG and matching 40A fuse or breaker. Then size each load for 15A, which is about 14AWG and a 15A fuse or breaker.

You match the fuse size in distribution to the wire size, not necessarily the load. Each load (save for lights probably) will have a fuse or breaker to protect it. If the load does not have a self protecting fuse, then you can fuse it appropriately. But even lights have a fuse, the filament itself will melt open. Ultimately the distribution fuse is designed primarily to protect the wire insulation from melting and causing a fire, not protection of the load.
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