Fuse rating for amp

[Dayvo]

Hi all . When installing an amp , is there a formula to work what the fuse rating should be between the battery and amp ? Thanks in advance

 

[Towcar]

The fuse to use is to protect the cable not the amp so it doesn't matter so much, I used a 100a between the cable and the amp, remember this is to protect against a big short that could cause a fire, it should be as close to the battery as possible. I have used circuit breakers and ANL fuses for this.

My reckoning for chosing the fuse size was adding up all the fuses in my amps and running with that, not that they would ever draw that much current but as above I was protecting the cable not the amps.

 

[VT13]

As stated the fuse on your power wire is all about stopping the power wire from catching fire if it is shorted/overloaded and nothing to do with protecting the amp/s. Amps have there own fuses downstream.

To safely protect the power wire the fuse needs to be of a lower current rating than the wire itself. The overall current capacity of our wire is a function of it's gauge and length, thicker (lower) gauge handles more current but the maximum rating reduces over the length of wire (2ft of 4 gauge will handle more current than 20ft). Anyway you can search for AWG recommended current ratings online and should find a table showing max recommended current for various lengths of AWG.

In general 60A is fine on 8AWG and 100A on 4AWG. This leaves a nice margin of safety and will ensure you don't flame up your power wire beyond the fuse. If you approach or exceed the max current rating of the wire you effectively have no fuse as the wire will overload before the fuse feels compelled to act.

For power wire, over spec is better than under spec but many people go way beyond and run massive 2AWG or lower when 8AWG is all that is needed. If your amp/s max combined load is under 500wrms total an 8AWG is more than adequate and 4AWG is generally safe through to 1000wrms.

 

[Dayvo]

Thanks guys it all makes sense now . Cheers