fuse sizes for fuse block?

As you can see in my pictures of my amp rack (in the gallery) I am running a 4-way Stinger Fuse Block.  Okay, cool and normal so far.  I have a nice supply of 60 amp and 100 amp fuses for it.  I also have an additional single-fuse block with a 100amp ANL fuse but am not going to use it.

So here is my dilema: I was going to run a 100 amp AGU fuse (yes, they were hard to find and not cheap) from my fuse block to the distribution block which will in turn send power to all 3 amps and one crossover via a distribution block.  The trouble is, I have a local car audio retailer keep telling me this won't work.  I don't believe him because he has always been like this.  Nothing will work, according to him, unless I buy his item for $50-75.  He cuts down everything I say I'm going to use and always tries to sell me something I don't want or need.  In fact, I have several items I already got conned into buying from him that are  just sitting in my "junk" drawer in the tool box.

I figured he was just trying to sell me more expensive stuff when he said my inline 100amp fuse will be too small, and that I need to buy his fuse block that accepts (and comes with) two ANL 250-amp fuses, and also accepts a pair of AGU fuses. It's an odd contraption, but looks cool other than it is pewter color and won't match any of my gold items. And at $50 (which is more than I paid for my Stinger fuse block) I think he is just trying to get my money.

I tried to explain to the guy that EACH component of my amp rack has its own seperate fuses inside them already, and that the added inline fuse is just a safety precaution.  I learned years ago that the whole idea behind inline fuses is to protect the components IN CASE of a short circuit somewhere along the power cable, NOT from amp overload.  And since my power cable to the main 4-way AGU fuse block is going to be only about 2 feet long, coming across the underside of my MDF amp rack, from the battery mounted right there in the trunk, I couldn't possibly have a short across this 1-gauge cable.

But then the local guy is trying to say this: "How many amps are the fuses in your components?" to which I gave him each amplifier's fuse rating, and the x-over's.  He added them all up and said 100 amp fuse will be too small, I need the bigger more expensive 250 amp fuse.  WHY? To me, that sounds like far too high of a rating. Each of two amp's fuses are 40amp and one amp's fuse ratings are a pair of 30amps, but the x-over is a mere 3amp because apparently is doesn't draw much load.

So he is trying to tell me to add all of these to get a minimum fuse rating: 40+40+30+30+3 = 143 total, so he thinks I need a fuse in my fuse block of at least a rating above 140 amps.  I tell him he is an idiot (although not in those words). I told him "My gains will only most likely be set to half (max) and that fuses are rated at a Maximum Current, so unless I push my amps to their peak output and crank my system to full volume all day long, there should be no need to even worry about blowing fuses"! He keeps assuming that the second I power up my system, the fuse is going to blow.  Apparently he hasn't fully became aware of what fuses are actually meant for. I think the guy is trippin'.

Am I right here or is this guy right? Do I really need 1 fuse in my fuse block that is rated the same as the total of all four fused components?  Or is he trying to sell me another thing I don't need?  The guy is probably 10 years younger than I am, and just because he is an importer of some name brand audio and security products at an indoor asian flea market does not mean he is an expert.

Oh, in case you are even wondering WHY I'm using a 4-way fuse block with only 1 fuse running to my power distribution block, it's because the other 3 fuses are running to: turn-on relay, a gauge, and a cool little fan that I'm going to hang from underside of rear deck that is made for motorhome dashes.  You know the kind.  So even though each amp has its own built-in fans, this added external fan will cool the entire rack.  If you look at the pics in thread in Gallerys ("mostly Kenwood in 98 Stratus) you might get a better idea of what I'm doing here.

I didn't feel like reading your entire post to see if you listed the size of the wire that runs from your battery to the fuse block,  what size is that wire?

There are two thoughts on it - fuse for the maximum safe current of the wire or fuse for the max expected load.

So, technically you are both "right".

I support your efforts though - there is no point in putting a 240A fuse on a MAX 143A load.  The bigger the fuse, the longer it will take to blow (even in a direct short situation).  Remember that the fuses in your amps, like you said, are the absolute max current, then a little extra for headroom.  If you are not bridging your amps down to the lowest possible load your amps won't pull near that current. 

The bottom line is you may be able to slide by with the 100A fuse depending on the load you put on the amps.  If you are using all three amps as sub amps and they are all bridged to the lowest load then you'll probably need a slighly larger fuse - like a 120A or so.   Since you've already bought the 100A fuse throw it in and see if you blow it.  If you do, replace it with something bigger.

First off, I want to apologize for posting this in the wrong Forum.  I accidently clicked on Motorcycle Electronics by mistake, thanks to a lack of coffee not a lack of respect for the forum or even a lack of brain cells.  I'll be more careful next time.  I know I'm not able to move it but maybe the administrator or moderator will.

Okay, my power cable from the battery, which is going to be right next to the amp rack, is 1 gauge, with 4 gauge power cables to each unit.

Of the 3 amps, 1 is for front stage, 1 is for rear stage, and 1 is for subs only. Front & rear are 2 channel, while sub amp is mono block amp.

I don't plan on running my DVC subs down to 1 ohm if I can avoid it, so I'm hoping to not load the mono amp too much.

Just for the sake of not seeming like a total idiot, I just bought a 175 amp ANL fuse from my local stereo place (a different guy) and am considering purchasing a circuit breaker to replace the main power's inline fuse. I couldn't find a 140amp fuse, so 175 is going to have to do IF I decide to use it.  They did have a 140-amp circuite breaker but it was a cheap one and the guy (this place is less sales hungry) talked me out of it because he admitted it was a cheap one and knows my system and said for what I've invested so far I should invest in a top brand CB like Stinger.  I'm going to check into them.

But he did show me a Kinetics battery that basically looks like big motorcycle battery.  I thought it was sweet, but almost as much in cost as I paid for my Optima Yellow Top so I withheld my desire to buy it. I want to check into what people say about them first.

Thanks for all your advice so far, and also thanks for not slamming me for mistakingly posting in the wrong topic.

So, your sub amp will pull 60A if driven hard and your front amps will pull half of their fused current, IF that much.  That's 100A (60+20+20).  Your crossover can be ignored, it will pull less then 500mA most likely.

For your particular setup I would think a 100A fuse would be sufficient. 

Keep in mind that fuses don't immidiately blow at their rated current - most fuses at that size take a fairly long time to blow at their rated current.  Check out this datasheet for examples: http://www.littelfuse.com/data/en/Data_Sheets/FK3_32V.pdf.  I realize that that is a maxi fuse, but they do have a 100A version, I couldn't find a datasheet for a 100A AGU fuse.  According to the sheet, at 110% of the rated current the fuse will take 100 hours to blow!  At 135% of the rated current the fuse will take 60 seconds to blow.  This will allow for quick peaks to occur but not blow the fuse.  If you can, contact the place you bought the fuse from and see if they have any information about it.

Thanks, fellers!

Yeah, the power cable from the battery to the fuse block is 1g but is only less than 2 feet long if that, and the power wire from the fuse block to the distribution block is 4 gauge, then from the distribution block to each amp and crossover will be an 8g because I can't find spade terminals for power wires that will fit my amp or xover's connections.  If I could find a connector that accepted 4g wire I'd use it.  I already had to trim down the brand new Rockford Fosgate connectors I just bought so they would fit.  But even they only accept 4g.

I'm thinking the 100amp fuse will do since I'm safe since I'm not  going for any SPL records or joining any IASCA events.  Just cruising around town with nice toonage.

Thanks for the advice on the CB.  I thought they were cool.  But if you guys think they are more of a hassle then I'll save my money and use it to buy spare fuses.

Maybe, just maybe, I can run a seperate 1g-to-1g inline ANL fuse holder with a 150 amp fuse in it or even 140.  I'll figure it out on Tuesday when I price more stuff online.

UPDATE:  Just installed an inline ANL fuse holder for main power to fuse block.  Yep, you read that right!  I took everyone's advice.  So there is now a seperate fuse in the cable to the power distribution for the amps and crossover.