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SC Ink
07-15-2011, 10:36 AM
gonna be running (2) 4 AWG ground wires from (2) amps to a Tsunami distribution block. The block has one ground input and two ground outputs.

1. Would it be ok to use a 2 AWG wire from the distrubution block to the battery ground terminal? 18 - 24" length max

2. IF it is recommended to use 1/0 awg....does the ground wire HAVE to be insulated?

I can get my hands on 1/0 awg bare ground wire that is gonna be scrapped.

If necessary, I can always wrap it in flexible plastic conduit.

sandm
07-15-2011, 11:02 AM
personally, I'd always make sure it's wrapped. the little additional cost for wrapped wire adds an extra piece of mind and makes sure that a positive lead doesn't ever come in contact with the neg unwrapped lead and spark, starting a fire, especially if your batteries are anywhere near the engine compartment, as some boats are..
spend the few $$ for a good quality automotive 2gauge cable. I would think 2gauge should be within the specs of your system..

good luck :)

SC Ink
07-15-2011, 11:11 AM
I do have about 20 feet of the 2 AWG that is of high quality and well insulated.

It's actually rated for nuclear power distribution equipment :)



I was hoping the 2 awg would be sufficient to feed two 4 awg grounds.

If we were talking power cables, I wouldn't do this.

philwsailz
07-15-2011, 11:34 AM
I do have about 20 feet of the 2 AWG that is of high quality and well insulated.

It's actually rated for nuclear power distribution equipment :)



I was hoping the 2 awg would be sufficient to feed two 4 awg grounds.

If we were talking power cables, I wouldn't do this.

We are talking power cables....

You don't somehow think that less current flows through the negative cable than the positive cable do ya? Just checking... I know of some people who think the current only flows through the +12 side of the wiring. Depending on who you talk to, some will tell you that the direction of electron flow in a DC system is from the negative terminal of the battery through the electronics to the positive terminal. Your ground wiring absolutely needs to be as well thought out as the +12v side.

Okay off of that rant, since I think your comment above is actually talking more to the lack if insulation than current capabilites... :D

I went to the American Wire Gage sizing chart. Cross-sectional area is key. A #4AWG cable has a cross sectional area of 21.2 square millimeters. To get twice that area for the cable going between the distribution block and the battery we need AT LEAST 42.4 square millimeters and a single #1AWG cable is equivalent in area. To me, I think you at least the same total area if not more between the distribution block and the battery. 1/0 is more commmon than 1, so I would go with 1/0.


As for your situation, what is the 1/0 you can get? What type of cable is it? What metal is it made from? There might be some types of 1/0 that are still not really suitable for your installation. That being said, a car can be looked at as one giant uninsulated conductor, but it just goes against my grain to think of seeing a bare metal conductor running through your amp compartent. Assuming it is of approproate material and construction, I would probably still recommend encasing it in some flexible insulating conduit.

Lastly, how far are you really trying to run this cable? For a Moomba, I think you are talking a few feet, right? I am thining that for $20 - $30 you could buy the proper wire to do this per best recommendations here and with the amp manufacturers. I often tell people that it costs almost as much for the wire and wiring hardware as for the amps themselves. To skimp on the wire is to put your financial investment in amps at risk. I think you will be happier sucking it up and going out and simply buying the proper 1/0 wire to do the job totally right. You will sleep better knowing you did so... :)

Phil
Kicker

SC Ink
07-15-2011, 12:34 PM
thanks Phil...

that's what I was fishing for - an audio pro to tell me yes or no on the 2 awg for the ground.

The 1/0 cable I can get is made from 99.9% pure copper. Pretty unflexible stuff - it only has about a dozen strands.

It is used for grounding outdoor circuit breakers and transformers.

I'll just go but the insulated 1/0 - I already have crimp-on terminals for that size.

bergermaister
07-15-2011, 12:37 PM
Best $$ I found for 1/0 was buying bulk from an automotive battery shop at $6ft - they also referred to it as welding cable. Best price for this stuff through local hardware stores was around $10ft. Online prices were around $6ft but then add shipping and waiting for it so why bother. Also, if you know all your lengths and terminal needs the local battery shops can crimp and heatshrink them on the spot which is nice.

SC Ink
07-15-2011, 12:56 PM
Man that's expensive wire!

This being the "Space Coast", we have loads of shops that specialize in electrical surplus - one popular place is called "Skycraft" - it's even been shown on the Discovery Channel for the odd products they sell.

They sell the 1/0 awg at $2.50/foot and 4 awg is .98 cents/foot.

http://www.skycraftsurplus.com/index.aspx

sandm
07-15-2011, 01:56 PM
I agree with phil in the fact that you should mirror whatever you are using on the positive side, and ensure that the grounds are connected equally as well as the power supply. I have seen a lot of people that run an 8gauge wire to an amp, then use a 12 or 16 for the ground and just screw it to a painted part of the body..

I don't know that I necessarily agree with the sizing from 4 to 1/0 gauge automatically.
just because you used 4gauge wire to hook up the amps does not mean that they will draw enough current to "max out" the capacity of the wires.
my little soundstream amp in my pickup calls for 8gauge from the factory. I ran 4 from the battery back as that's what I had leftover and used a small distro block at the amp to drop down to 8 to hook up. my ground is 8 from the getgo. that amp has been going strong for 6 years, sometimes at some pretty hefty volume levels for long times and has never thermal'ed nor shows any audible signs of clipping.
if you are using 2 amps that call for 8 gauge and run 4, there is no reason that I see to run 1/0 to the battery as the amps should not ever over-draw the capacity of 2gauge.
someone once taught me to think of electrical in terms of water flowing through a pipe. if you're draw is only using 60% of the capacity of the line at full load, then you don't need that much more upsteam(or downstream, depending on how you view the water flow).

I concur with phil's basic thoughts not to skimp, but it's like gas. running 93 in a car that's designed to run on 87 is a complete waste of money :)

philwsailz
07-15-2011, 02:22 PM
I agree with phil in the fact that you should mirror whatever you are using on the positive side, and ensure that the grounds are connected equally as well as the power supply. I have seen a lot of people that run an 8gauge wire to an amp, then use a 12 or 16 for the ground and just screw it to a painted part of the body..

I don't know that I necessarily agree with the sizing from 4 to 1/0 gauge automatically.
just because you used 4gauge wire to hook up the amps does not mean that they will draw enough current to "max out" the capacity of the wires.
my little soundstream amp in my pickup calls for 8gauge from the factory. I ran 4 from the battery back as that's what I had leftover and used a small distro block at the amp to drop down to 8 to hook up. my ground is 8 from the getgo. that amp has been going strong for 6 years, sometimes at some pretty hefty volume levels for long times and has never thermal'ed nor shows any audible signs of clipping.
if you are using 2 amps that call for 8 gauge and run 4, there is no reason that I see to run 1/0 to the battery as the amps should not ever over-draw the capacity of 2gauge.
someone once taught me to think of electrical in terms of water flowing through a pipe. if you're draw is only using 60% of the capacity of the line at full load, then you don't need that much more upsteam(or downstream, depending on how you view the water flow).

I concur with phil's basic thoughts not to skimp, but it's like gas. running 93 in a car that's designed to run on 87 is a complete waste of money :)

Sorry sandm, this sounds confrontational, and I don't mean it to. I just want to clarify, and quoting you made most sense. :D


My post above assumes that each of SC Inc's two amps recommend or require 4 ga. To get an equivalent of two pulls of 4 ga. going all the way back to the battery, one needs 1/0 to ge tthe equivalent amount of copper in the power cable. This is just published fact.

What we don't know is the amplifier manufacturer recommendations, or the amp models. If in fact he has two amps that can run on 8 ga, the 2 ga primary wire will be fine, but we don't know that. In fact, if he has two amps that only recommend 8 ga, he can get away with using 4 ga as his primary wire, but again, we don't know that. I only wanted to create a clean wiring scheme that preserved the amount of cooper present in the two #4AWG cables between the amp and the distribution block, based on the facts provided.


For the record, I did have a boat manufacturer who was trying to outsmart the system a few years ago. He put a current meter on a functioning amp installed in a boat and he "determined" on his own that the current required to run the amp would allow a smaller power cable, so he went against Kicker recommendations for minimal power wiring size. He was using a wire he felt appropraite for measured current, and it was several sizes smaller than our recommendation. That year he had a huge problem with amplifiers overheating. They were overheating all ove the world. I spent money to go see him, spent money testing, all the while trying to tell him his wire was too small. We got nowhere, and he wouldn't budge.

Fall came and the problem went away, but it came back the next spring. He called and let me know he was having trouble. I asked him if he had gone in and fixed his wire issue yet. He got pissed, but decided he would PROVE to me that the issue was not his installation and wiring, so he went and built three boats with the wire we recommended and put them into service. Guess what? Overheating problem went away...... :D

Know that you cannot have too much copper from an installation standpoint. You can only have too much copper from a budget standpoint. If you only need #4AWG don't go buy #2AWG because you think it is better. You are only wasting money as stated. But if you try to cheat the deal, and use less wire, (smaller wire, bigger number) than what is recommended, you will usually get burned.

Bottom line, If you follow the recommendations from the guys who built your stuff, you will usually find that the system performs the way you need and want it to.

Phil
Kicker

SC Ink
07-15-2011, 03:28 PM
the amps I am installing are a JL marine M400/4 amp and an Exile Harpoon.

Both suggest the use of 4 awg wire for power and ground.

I am planning on running the power wire from each amp to the distribution block via 4 AWG, thru the MANL fuse, and then thru a 2 AWG wire to the battery.

I will remove the jumper plate from the distribution block, thus creating an inline fuse holder for each power wire.

I'm doing this because I have plenty of 2 AWG wire laying around the house.

I will run the two 4 awg ground wires into (1) 1/0 awg ground

philwsailz
07-15-2011, 03:42 PM
the amps I am installing are a JL marine M400/4 amp and an Exile Harpoon.

Both suggest the use of 4 awg wire for power and ground.

I am planning on running the power wire from each amp to the distribution block via 4 AWG, thru the MANL fuse, and then thru a 2 AWG wire to the battery.

I will remove the jumper plate from the distribution block, thus creating an inline fuse holder for each power wire.

I'm doing this because I have plenty of 2 AWG wire laying around the house.

I will run the two 4 awg ground wires into (1) 1/0 awg ground

Your #2 wire on the B+ side will be your potential bottleneck. It does not have the same cross-section as a pair of #4AWG conductors, FYI

Phil
Kicker

SC Ink
07-15-2011, 03:55 PM
One #4 going into one #2 (with a manl fuse inbetween)

twice.

philwsailz
07-15-2011, 04:07 PM
One #4 going into one #2 (with a manl fuse inbetween)

twice.

Oh!!!!

Each amp home runs to the batteries....

Gotcha! my bad. :)

Phil
Kicker

sandm
07-15-2011, 06:45 PM
Sorry sandm, this sounds confrontational, and I don't mean it to. I just want to clarify, and quoting you made most sense. :D


My post above assumes that each of SC Inc's two amps recommend or require 4 ga. To get an equivalent of two pulls of 4 ga. going all the way back to the battery, one needs 1/0 to ge tthe equivalent amount of copper in the power cable. This is just published fact.

What we don't know is the amplifier manufacturer recommendations, or the amp models. If in fact he has two amps that can run on 8 ga, the 2 ga primary wire will be fine, but we don't know that. In fact, if he has two amps that only recommend 8 ga, he can get away with using 4 ga as his primary wire, but again, we don't know that. I only wanted to create a clean wiring scheme that preserved the amount of cooper present in the two #4AWG cables between the amp and the distribution block, based on the facts provided.


Phil
Kicker

no worries phil. I agree with you, and was only pointing out that you don't need to automatically assume a 1/0. I would concur with the recommendation as you post it, but based on ed's response of having a ton of 2gauge lying around, I would wonder why you would not mimic the same run of ground wires as opposed to buying 1/0 other than the simplicity of running a single wire, except that you are already running 2 power wires.

EarmarkMarine
07-15-2011, 10:12 PM
I look at assessing the cable size a little differently.
Start by determining the maximum and collective fusing for all amplifiers. Note, its unlikely that you will ever draw this much current. Even though you can exceed the fuse rating for a certain duration before it blows the amplifier total fuse amperage also represents an extreme operating condition to protect the amplifier.
Once you have the total max current draw plus the total distance of the main run for both positive and negative then you want a gauge of primary wire that has low enough resistance that you will not have an appreciable voltage drop.
Once you have the correct size of primary supply positive and ground you can drop down a size after the distribution blocks for the extensions to the two or three amplifiers. Since the distribution blocks are typically as close to the amplifiers as possible its usually the short extensions that are overkill for their actual usage.
You would have to have a ton of power or terribly inefficient amplifiers to compromise the amplifiers' performance using 2-gauge cable for a short primary run within the port locker. However, if there is considerable separation between the batteries and amplifiers this could change the requirements.
I would definitely trust 2-gauge to handle 150 to 200 amps of total potential draw over a couple of feet. And then step down to 4-gauge for the two or three very short individual extensions.
Remember that we may have an 8-foot positive and 8-foot negative for a total loop of 16 feet in many boats. A car may have a 17-foot positive run to the battery and a 2-foot negative run to the car body or frame. In many cars I would trust the longer 1 or 2-gauge ground cable before trusting the conductive properties of the car body.
So begin with the larger primary run based on your collective current draw. The smaller and shorter extensions at a step down in wire gauge are going to be plenty.

David
Earmark Marine