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amp install question

Old 10-06-2002, 10:36 AM
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Another thing that helps a lot is to keep the ohms load to 4ohms or more. The lower ohm loads draw more power and also create a lot more heat in the amp.

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Old 10-06-2002, 12:02 PM
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After reading your posts I will run 4ga power wire to the amps. Now for the ground wires: Will there be a problem if I run a 4ga from the battery and then go into 2 8ga wires that will go into the amps. I always heard that each amp needs its own separate ground wire back to the battery. My amps have capacity for 8ga power and ground wires. I'm trying to keep this as simple as possible.
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Old 10-06-2002, 12:51 PM
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Simple is good. However you do the power also do the ground. Keep it the same. Good luck! Craig
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Old 10-06-2002, 12:51 PM
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no you can put them both on the 4 ga block but also to avoid a ground loop condition your stereo must also ground to the same
point mutiple grounds will usually cause a ground loop which will pick up the ingnition and can be heard as background noise.
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Old 10-06-2002, 01:18 PM
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I would run 2 seperate power feeds and 2 seperate grounds- the voltage drops, etc. caused by one amp will also show up at the second amp with common leads.

Amp capacity of wire is determined not only by conductor size, but also the insulation temperature rating (rating is degrees C). Most wet location rated insulations have a 75 degree rating, and some have a 60 degree rating. The wet location types will generally have a 'W' in the wire type classsification, which should be stamped on the insulation. Some common wet use insulation types are TW, THW, THWN. I don't have marine types handy and don't want to go by memory. Heres an example from the National Electrical Code:

size# 75 deg, amps 90 deg, amps
10 35 40
8 50 55
6 65 75
4 85 95

For fire protection and compliance with National Electrical Code, the wire should be protected for the rated amperage, or the next higher amperage if no exact fuse is available. The overcurrent protection is ideally to be located at the source point, but with a battery setup this is not always possible.

On automobiles they use fusible links which are fuse wire- sometimes directly at the battery and sometines from a terminal point mounted near the battery.

The Coast Guard does require compliance with National Electrical Code- so it looks good to them if they ever start inspecting that closely, too.

Also, you should always provide overcurrent protection at each point at which conductor sizes change. An 85 amp fuse on a #4 main feed will not protect a #8 wire connected to it!

I would run the 2 #8 positive conductors from the battery to a fuse block mounted as close to the batteries as possible, Each #8 wire then feeds a fuse,such as a 50 amp for #8 75 degree rated wire. then feed the amps from that point. Or, get some fusible links, with spares.

The fuse or breaker you install can be rated somewhat higher than what is installed in the amp as long as it is sized to protect the wire. If the amp has a 30 amp fuse and you select a 40 or 50 amp main fuse, the fuse in the amp would normally blow first due to a lower amp rating. The fusible link or main fuse will blow only for a short or overload between the main fuse and amp.

I hope this helps!!!!
Bulldog aka Ronnie

Last edited by Bulldog; 10-06-2002 at 01:21 PM.
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Old 10-06-2002, 04:36 PM
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I would oversize the wires up to #6 for each amp-- The lower voltage drop will help keep the amps cooler and the cost difference isn't much. You won't be sorry. I just bought a 75x4-200x1 sub amp that I plan on putting in my boat. I mounted the 1500 W inverter ( works the same as a sterio amp in a lot of ways ) under the back seat ( on the vertical part of the back seat that faces the cockpit) it stays nice and dry and is well ventilated and close to the batteries. I plan on mounting the sterio amp on the other side.
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