blowing fuses in distribution block?

(dbo) · (dbo) **Join Date: Feb 2004** 07-04-2004, 5:29 PM

all of my fuses are blowing in my distribution block when i turn my stereo on. it is a stinger block with two 4 gauge wires in and four 8's out. the biggest amp fuse i could find was 30 amp. those are the only ones i could find to fit. the amps have about 4000 watts. are the fuses too small to handle the power, which i dont beleive or is it usually a short somewhere and if so where the wires to the batteries are less than 3 feet long and have no marks on them. any input will be appreciated and thanks.

(rodmcinnis) · (rodmcinnis) **Join Date: Sep 2002** 07-08-2004, 8:36 PM

Derek:
I don't understand what you mean by "all of my fuses are blowing". How many fuses are there in this block? Do you mean that you blow them, one at at time as you replace them, or something happens and all the fuses in the block blow?

If you are blowing multiple fuses at one time then there is something seriously wrong with your electrical system!

You also refer to amps (plural). Do the amps total 4000 watts, or is each amp 4000 watts?

It is very unlikely that the amps deliver full power for more than an instant, but during that instant the amps will need to draw 333 amps! That's about 10 times the rating on that 30 amp fuse you are trying to use which will pop it pretty darn fast.

To handle that kind of power you should have a dedicated wire fused at the battery. Attempting to power the amps from the boat's distribution fuse block will only cause all sorts of problems.

Rod

(mujibur) · (mujibur) **Join Date: May 2002** 07-08-2004, 9:26 PM

Replace the fuses with tin foil ;-)

Seriously - 4000 watts RMS will draw about 120 amps at 14 volts... 30 amp fuses will not get it done if i read your setup correct.

(bob) · (bob) **Join Date: Feb 2001** 07-09-2004, 10:44 AM

sorry Muji but the formula for current is power / voltage = current or 4000 / 12 = 333 amps at the very most or if volts are at 13.8 = 289

(the_madness) · (the_madness) **Join Date: May 2003** 07-09-2004, 1:43 PM

Is your battery fully charged? This is a guess but if the battery is low on charge and only supplying say 10 volts, wouldn't the 4000 watts of amplifier would draw 400 amps?

(the_madness) · (the_madness) **Join Date: May 2003** 07-09-2004, 1:45 PM

Also, what happens if you disconnect all but say on amplifier, do the fuses still blow?

bluemalibu 07-09-2004, 4:19 PM

Brad Duffy - You just stumbled onto one of the big reasons you need to have a strong battery package, and a strong charging system to run a high wattage stereo. Yes as voltage drops, current raises - IF output stays the same. Lower voltage / higher current means more heat, and can kill amps, head units, and other electronics.
Geoff

(mujibur) · (mujibur) **Join Date: May 2002** 07-09-2004, 9:18 PM

Bob - sorry i did not clarify.

Most applications/equipment do not use 100% of the continuously rated RMS ( this is usually PEAK with tons of noise, not continuous)of the amplifier - on average about 38% of the continuous rating of a good amplifier is used if the system has subwoofers installed mixed with component sized speakers. Technically if the 4000 watts RMS is a real rating, then my calculation estimated that the amp are more than likely only using a max of about 1520 watts = 108 amps draw at 14 volts. I think the point i was really trying to make was that even in optimal conditions if the RMS ratings are real then 30 amp fuses are not enough and there are of course other factors, load on the amp, faulty equipment causing more draw by showing less resistance (shorts, bad output devices - usually fets of some sort, etc.). Anyways we really need more data to help Derek out like brand of amp, load of speakers connected to the amp and wire length to the amp to calculate the real draw of current.