# 4 Gauge Wire Required? 60A fuse, can I use 8 gauge?



## jcmsupport (Jan 14, 2012)

I have a Punch amp that is rated at 560 RMS via 2 OHM load. It uses 2 30A which equals 60. It states 8 gauge is fine for that amp.

However, I want to buy this amp:

ROCKFORD FOSGATE PRIME SERIES CLASS D 750W RMS 1 CHANNEL FULL RANGE AMPLIFIER | eBay

It states 4 Gauge is required. An in-line 60A fuse is recommended, in which I would just swap out the old punch 500 for the new guy above to get 100 RMS more. 

Doing the math, I'm going to assume the Punch amp is underrated like the current one I have in which it's 60 RMS more. So it's 660 RMS with the new amp divided by 12v (my battery) and I get 55 Amps which should be ok under the 60A fuse.

Now, I have KnuKonceptz wire, I have a 150A miniANL via 4 gauge going to 2 distro blocks that output 8 gauge, all KnuKonceptz.

According to Knu: Knukonceptz product detail for KOLOSSUS FLEKS KABLE 8 GAUGE BLACK POWER/GROUND WIRE

Their 8 in which I have is Max load 60A @ 20' with 805 stands. Question is, I should be able to use the amp above no problem simply switching it out with the old punch to acquire just 100 RMS more. I would be powered just 120.9 Kappa Subs at 350 RMS each. 

The impedance is switchable with these subs from 2 to 4 OHM. I'd set it to 4 as they are SVC and wiring them both to a 2 OHM load. Thus getting around 660 each with the new amp above, rather then 550 each with the Punch amp I have. 

Mind you, I don't feel like upgrading at this time the wiring. But why not spend just an extra 100 for a slimmer amp if I can get away with 100 RMS more to cater to the 700 load that my subs would be optimal at.

Any input would be appreciated!


----------



## ATOMICTECH62 (Jan 24, 2009)

If you are only running a foot or two of 8ga from the dist and have 4ga to the battery you are fine.if you are running 8ga to the battery you should upgrade it to 4ga regardless.


----------



## jcmsupport (Jan 14, 2012)

ATOMICTECH62 said:


> If you are only running a foot or two of 8ga from the dist and have 4ga to the battery you are fine.if you are running 8ga to the battery you should upgrade it to 4ga regardless.


It's simply 4 to 8 via the distro block. A foot you say? I think it's less then that, give or take a foot. I should be ok right with the in-fuse in place?


----------



## ATOMICTECH62 (Jan 24, 2009)

Yes.No problem.


----------



## ATOMICTECH62 (Jan 24, 2009)

Why dont you just get another 1 foot piece of 4ga if it makes you feel comfortable.
A lot of shops will just give you a piece for free.I would.


----------



## jcmsupport (Jan 14, 2012)

ATOMICTECH62 said:


> Why dont you just get another 1 foot piece of 4ga if it makes you feel comfortable.
> A lot of shops will just give you a piece for free.I would.


I don't believe you can go 4 gauge to 4 gauge, I have to go 4 to 8 gauge.


----------



## MarkZ (Dec 5, 2005)

The 8ga coming from your distro block is perfectly fine.


----------



## jcmsupport (Jan 14, 2012)

MarkZ said:


> The 8ga coming from your distro block is perfectly fine.


Hey, I appreciate the response, I mean, doing the math, it should be alright.


----------



## kyheng (Jan 31, 2007)

The Knu's 8AWG OFC can take [email protected]
Certain company require you to use 4AWG is because most of the power cables in the market are over rated....


----------



## lbp775 (Jul 7, 2011)

jcmsupport said:


> I don't believe you can go 4 gauge to 4 gauge, I have to go 4 to 8 gauge.


Why can't you do this? I have a fused distro that has 4 gauge in/out. Is this not recommended?


----------



## minbari (Mar 3, 2011)

lbp775 said:


> Why can't you do this? I have a fused distro that has 4 gauge in/out. Is this not recommended?


I think he means that the one he has wont do it.


----------



## jcmsupport (Jan 14, 2012)

minbari said:


> I think he means that the one he has wont do it.


No, I was always told that you have to go from 0 to 4 and from 4 to 8 when doing distro blocks, unless I'm wrong?


----------



## kyheng (Jan 31, 2007)

True 1/0AWG can deliver 250-300A of current
4AWG about 100-150A of current
8AWG about 60A of current
Just say your amp only requires 40A, it is pointless to use a 4AWG cable....


----------



## bfowler (Nov 25, 2009)

jcmsupport said:


> No, I was always told that you have to go from 0 to 4 and from 4 to 8 when doing distro blocks, unless I'm wrong?


yes, thats wrong. if your d-block has the correct size outputs to do it, there no reason not to.


----------



## King Nothing (Oct 10, 2005)

My MTX 2300 with 90 amps of fusing and known to do 8-900w bridged only has 8 gauge power and ground inputs


----------



## adamtwo4 (Jan 8, 2012)

What about a class d with 600 watts? Would 8 gauge be okay from distribution block to amp, (couple feet) or should I go 4?


----------



## kyheng (Jan 31, 2007)

For main, 4AWG are good, but for short lenght after distribution block, 8AWG will be good....


----------



## KBT2011 (Dec 29, 2011)

kyheng said:


> True 1/0AWG can deliver 250-300A of current
> 4AWG about 100-150A of current
> 8AWG about 60A of current
> Just say your amp only requires 40A, it is pointless to use a 4AWG cable....


So if you have 4AWG running to battery on a 100A fuse then you have 8AWG coming off of a fused distro block, what would each fuse size be at the distro? I've seen a calculator at my power outage that says 25A fuses each, but that seems small.


----------



## minbari (Mar 3, 2011)

jcmsupport said:


> No, I was always told that you have to go from 0 to 4 and from 4 to 8 when doing distro blocks, unless I'm wrong?


there is no reason for that. as long as you are not exceeding the 0ga current with 2 or more items connected to it, then it doesnt matter. 

now, it you are pulling max current for a 0ga on EACH branch of a distro, then ya, you are going to exceed the main line cable by 3X. some common sense will tell you how to config this.



KBT2011 said:


> So if you have 4AWG running to battery on a 100A fuse then you have 8AWG coming off of a fused distro block, what would each fuse size be at the distro? I've seen a calculator at my power outage that says 25A fuses each, but that seems small.


ussualy the runs off the distro are very short so 8ga will work just fine. if you want to use 4ga there too, doesnt matter, then you dont have to buy two different sizes of wire. as for fuses off the distro, I ussualy just fuse it based on what the protection for the amplifier requires (as long as that doesnt exceed the wire of course)


----------



## KBT2011 (Dec 29, 2011)

minbari said:


> there is no reason for that. as long as you are not exceeding the 0ga current with 2 or more items connected to it, then it doesnt matter.
> 
> now, it you are pulling max current for a 0ga on EACH branch of a distro, then ya, you are going to exceed the main line cable by 3X. some common sense will tell you how to config this.
> 
> ...


Both my amps require 100A according to their booklets. RF T500-1bd and T400-4 will be running both at 4 ohms. So I'm gonna try a 25A fuse each but I think they will blow...


----------



## pionkej (Feb 29, 2008)

Another thing to remember is that an amp won't be drawing anywhere near full power 90% of the time with music. I'm currently running a JL HD900/5, JL HD600/4, Infinity Kappa FOUR, and JBL MS8 all from a single 4ga run from the battery to the disto (8ga from distro to amps) and I've had zero issues. No blown fuses. No warm wires. No headlight dimming. No "choked" output.


----------



## minbari (Mar 3, 2011)

KBT2011 said:


> Both my amps require 100A according to their booklets. RF T500-1bd and T400-4 will be running both at 4 ohms. So I'm gonna try a 25A fuse each but I think they will blow...


dont even bother, if they require 100amps each, then you need to fuse for 100A for each amplifier at the distro and 200A at the battery. in this case 4ga is not going to cut it either. you need 1 or 2ga


----------



## MarkZ (Dec 5, 2005)

4ga will be fine, for the reasons pionkej stated. If you want to minimize vdrop, then run the thickest wire you feel comfortable with. But don't expect an audible difference, and there certainly won't be any safety hazard in using smaller wire.

Another thing to consider re: fusing, is that fuses blow pretty quickly. Much faster than 4ga wire heats up and usually slower than a pn junction breaks down. The amps themselves are not able to withstand the kind of current that it would take to heat up a 4ga wire. The fuses are just there to prevent shorts from starting fires.


----------



## KBT2011 (Dec 29, 2011)

minbari said:


> dont even bother, if they require 100amps each, then you need to fuse for 100A for each amplifier at the distro and 200A at the battery. in this case 4ga is not going to cut it either. you need 1 or 2ga


I'm running 325W RMS at the mono amp and 300W RMS at the 4 channel amp, do I really need 1 or 2 AWG?


----------



## pionkej (Feb 29, 2008)

KBT2011 said:


> I'm running 325W RMS at the mono amp and 300W RMS at the 4 channel amp, do I really need 1 or 2 AWG?


I don't think so. If you have plans to go larger in the future, it's cheaper/easier to buy big once and install it once. If you feel pretty good about what you're running now, 4ga will be fine. 

Another tip for power conservation, run ported or IB for your subs. They need the most power, and those alignments have 1/2 to 1/4 the apparent load on the amp. Even a 6db slope at 20hz helps a ton with sealed enclosures. Easier on subs, easier on amps, easier on the cars electrical system.


----------



## KBT2011 (Dec 29, 2011)

pionkej said:


> I don't think so. If you have plans to go larger in the future, it's cheaper/easier to buy big once and install it once. If you feel pretty good about what you're running now, 4ga will be fine.
> 
> Another tip for power conservation, run ported or IB for your subs. They need the most power, and those alignments have 1/2 to 1/4 the apparent load on the amp. Even a 6db slope at 20hz helps a ton with sealed enclosures. Easier on subs, easier on amps, easier on the cars electrical system.


Ok cool well to start out I'm gonna try a 100A fuse at the battery, and two 50A fuses at the distro. Although each amp calls for 100A the T500-1bd manual says put a 100A fuse at the battery and an additional 100A at the distro for additional amps, so 100/2 = 2 50A AGU fuses....hopefully lol


----------



## minbari (Mar 3, 2011)

KBT2011 said:


> I'm running 325W RMS at the mono amp and 300W RMS at the 4 channel amp, do I really need 1 or 2 AWG?


misread it, thought you said you had the T1500, not the T500

4ga will be fine for that.


----------



## KBT2011 (Dec 29, 2011)

minbari said:


> misread it, thought you said you had the T1500, not the T500
> 
> 4ga will be fine for that.


Ah I see, you had me a sweat for a second there I was like WTF haha. Thanks for the help though, this noobie appreciates every bit he can get :laugh:


----------



## MarkZ (Dec 5, 2005)

KBT2011 said:


> Ok cool well to start out I'm gonna try a 100A fuse at the battery, and two 50A fuses at the distro. Although each amp calls for 100A the T500-1bd manual says put a 100A fuse at the battery and an additional 100A at the distro for additional amps, so 100/2 = 2 50A AGU fuses....hopefully lol


The manual is kinda stupid then. 

I'd go with a single 50A (or thereabouts) slow blow fuse at the battery and call it a day. You don't gain anything by having multiple fuses in series, and it seems highly unlikely that your pair of amps will draw more current than that.


----------



## minbari (Mar 3, 2011)

MarkZ said:


> The manual is kinda stupid then.
> 
> I'd go with a single 50A (or thereabouts) slow blow fuse at the battery and call it a day. You don't gain anything by having multiple fuses in series, and it seems highly unlikely that your pair of amps will draw more current than that.


agreed. I had an 800 watt system in the 90s that was all class A/B and ran a single 50A fuse. although it did get the fuse hot enough to wiggle it loose after about 6 months, it never did truely blow.


----------



## KBT2011 (Dec 29, 2011)

MarkZ said:


> The manual is kinda stupid then.
> 
> I'd go with a single 50A (or thereabouts) slow blow fuse at the battery and call it a day. You don't gain anything by having multiple fuses in series, and it seems highly unlikely that your pair of amps will draw more current than that.


Well neither amp has on board fuses. I was just going to fuse the distribution and at the battery.


----------



## sqshoestring (Jun 19, 2007)

100 extra watts is not going to get you much more either unless the amps are rated differently. It might be enough to notice, I can notice 350 to 500 on mine but its maybe 20% more output just a guess. It has more punch at high output with more power, could be the 350 is peaking out.

If you have question go to bcae1.com the wire page there are calculators and charts. One will show you the loss on every part of the wire. Mostly if the 8ga is short its no problem it will handle the power, its just that it has a loss _per foot_ and that is why you don't want 15' of it to the battery. If you never play it over 80% it would never matter, that is only time it will pull full current is at 80-90% and more.

I was running a 4x125 class D and 1x500rms class D on a single 5ga wire, it will dim some but mostly only at idle. I don't crank it full on at night that much anyway so don't care, in fact I don't do that very often at any time. Now have a 350 on subs it dims at idle a little, its funny the sub amp has half the fuse the 4ch does.


----------



## jcmsupport (Jan 14, 2012)

sqshoestring said:


> 100 extra watts is not going to get you much more either unless the amps are rated differently. It might be enough to notice, I can notice 350 to 500 on mine but its maybe 20% more output just a guess. It has more punch at high output with more power, could be the 350 is peaking out.
> 
> If you have question go to bcae1.com the wire page there are calculators and charts. One will show you the loss on every part of the wire. Mostly if the 8ga is short its no problem it will handle the power, its just that it has a loss _per foot_ and that is why you don't want 15' of it to the battery. If you never play it over 80% it would never matter, that is only time it will pull full current is at 80-90% and more.
> 
> I was running a 4x125 class D and 1x500rms class D on a single 5ga wire, it will dim some but mostly only at idle. I don't crank it full on at night that much anyway so don't care, in fact I don't do that very often at any time. Now have a 350 on subs it dims at idle a little, its funny the sub amp has half the fuse the 4ch does.


Ya, that's odd huh! I have a Punch 4 Channel with an 80A that runs 400 watts, or 100 each component speaker at 2 OHM. 400 RMS divided by 12 (Voltage on Battery) is 33.3 AMPS which is by all means no where near the 80A draw. So why have a fuse that high? Might be a Fosgate thing? I mean, I see amps rated the same RMS and it has a 40A fuse which makes sense. What I want to do since I already have a 4 Gauge as main is get a distro block that is 2/4 in and 4/8 out. 

Simply rig up the 4 in and have 2 4 out. Fuse the 4 channel at 80A with an AGU fuse at 80A and get an amp, the Fosgate Prime 1200 which does 1200 RMS at 1 OHM stable. 1200 RMS divided by 12 again is 100 AMPS. The main 4 gauge for power is 150A MiniANL. Shouldn't be a problem I would assume as all the power would go to the sub. I'd still be under 140A give or take according to the math.

Maybe I should put a 60A fuse for the Punch amp at 80A?


----------



## MarkZ (Dec 5, 2005)

KBT2011 said:


> Well neither amp has on board fuses. I was just going to fuse the distribution and at the battery.


Yeah, but what is that going to do? On board fuses are kinda stupid too  . Well, I shouldn't say all onboard fuses... some companies just fuse the voltage rails and/or the primary side, which makes SOME sense (though is still a little stupid, because all the silicon and carbon parts in the amp will pop first  ). The only way to really protect components is with a crowbar circuit, and nobody uses those in amps.

The fuse is there to prevent widespread damage. If you blow something up, it makes sure that it doesn't fail short, draw a bunch of current, and start a fire. The fuse at the battery will do that. The other fuses won't add any additional protection.

The only benefit I can see would be if the failure was so immediate that it blew only the distro fuse and not the main fuse, and left the other amp going fine so you could still listen to music until you replaced amp #2. Limp home mode, so to speak.


----------



## kyheng (Jan 31, 2007)

KBT2011 said:


> So if you have 4AWG running to battery on a 100A fuse then you have 8AWG coming off of a fused distro block, what would each fuse size be at the distro? I've seen a calculator at my power outage that says 25A fuses each, but that seems small.


From main, 100A are ok, but at distribution block to your amp(s), better follow what the amp requires...


----------



## jcmsupport (Jan 14, 2012)

kyheng said:


> From main, 100A are ok, but at distribution block to your amp(s), better follow what the amp requires...


What I would do is go by the RMS and then divide by 12 which is the current voltage of your battery. So if you have a 400 amp and you are running 400 RMS divide that by 12 and you get 33.3 in which case a 40A fuse would be ok.


----------



## kyheng (Jan 31, 2007)

I won't calculate it like that.... Amp's efficiencies are more important over here.... In real life listening, it is only 10-30% from the rated, unless you are a robot that only likes test tones, then you may be pulling 100%.....


----------



## passtim (Sep 30, 2009)

KBT2011 said:


> Well neither amp has on board fuses. I was just going to fuse the distribution and at the battery.


Sorry, getting late to the party, I used a T1500-1bd and the T-400/4 with a 150a breaker and 30 amp for the t400 and 100 for the T1500 and never tripped/blew a fuse so at a four ohm load on the 400, a 30 amp fuse on your distro block is sufficient. This worked even with all 4 channels bridged at 2 ohms also.


----------

