Power wire gauge (specific setup)

Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=10416
Printed Date: July 13, 2025 at 1:49 PM

Topic: Power wire gauge (specific setup)

Posted By: rbr28
Subject: Power wire gauge (specific setup)
Date Posted: March 04, 2003 at 9:15 AM

I have seen a million guides suggesting the proper wire gauge for specific situations, but they all vary quite a bit. I currently have about 14 feet of 8 gauge Streetwires cable running from my battery to a distribution block. I then have 8 gauge from that to a Alpine 7894 head unit, and a Kenwood PS200T power amplifier. The Alpine is rated at 27wx4 RMS and 60wx4 max. There is a single 20 amp fuse on the power wire that came with the unit. The Kenwood Amp is rated at 75wx2RMS, 150wx2Max. The amp is bridged for a sub and the bridged power rating is 300W rms, and 600W max. The unit has two 20 amp fuses, I'm guessing 1 for each channel.

So here's my dillema. If you add all that up, you obviously come up with very different numbers depending on what you go with. If you go with amps, which to me makes the most sense, I can only draw 60 amps max from this setup. Am I correct in that assumption? If that's correct, the 8 gauge for a 14 foot run seems fine for my setup. On the other hand, if I figure the maximum power output, it would come out at 840W and 8 gauge seems insufficient for that. My guess is that the manufacturer's power outputs are over-inflated and that the total amp draw is a more reliable means of determining the wire to use, but I'm wondering what everyone else thinks. It would only cost me about 20$ to run 4 gauge, but I'm not thrilled about widening the hole in my firewall, and running new cable unless the gain is significant.

Replies:

Posted By: the12volt
Date Posted: March 04, 2003 at 9:44 AM

Yes, you are correct in your assumption, but when in doubt always go with the heavier gauge wire. With an RMS rating of 420 watts over a 14 foot run, I'd recommend 4 gauge. It's highly unlikely you will ever exceed a maximum sustained current draw of 60 amps with the two amplifiers you listed above even at their maximum output. Even if they could provide 840 watts of sustained output, current draw at 12 volts would be 70 amps, at 13 volts it would be 64.62 :)

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Posted By: themagicone
Date Posted: March 04, 2003 at 10:12 AM

you really dont need to run your deck off of a 8 guage power wire. If you dont want to use the factory power in the harness a 10 gauge to the battery would be fine, then the 8 gauge for your amp would be fine.

Posted By: the12volt
Date Posted: March 04, 2003 at 10:18 AM

My bad, I read your post as two amplifers, not as a head unit and one amplifier. 8 gauge will be fine for your amplifier.

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Posted By: donkason
Date Posted: March 17, 2003 at 7:22 PM

Always use a bigger wire when in doubt. I would use a 4 ga. wire.