High Amp Fuse?

[slsbl77]

I have recently become aware of the need of a big? fuse between the aux battery in my '07 2500 cargo and my 3000 W Aims inverter, thankfully not thru personal experience....
I want to avoid any sort of catastrophic failure, I believe the fuse would go between the aux battery positive cable and the battery itself???
The biggest draw on my inverter is a machine which draws 25 amps on startup then "cruises" at approximately 12 amps.
What would be an appropriate amperage fuse??

Thanks, Bob

[sikwan]

Your instruction manual should tell you the minimum fuse rating and wire gauge size.

For your inverter size, it'll be over the 200A rating fuse.

[OrioN]

If your drawing 25 AC amps , even momentarily, i believe a 400amp fuse is more inline (pun intended).
25 AC amps = +270amps dc and you need to consider that other stuff is already drawing on the battery at the same time.
I use this one on my Xantrex rs3000...

http://www.xantrex.com/web/id/117/p/1/pt/8/product.asp

[rlent]

As I understand it, your fusing should be sized for the cable you are using.

My cabling is double-ought (2/0) which is huge and probably overkill (but intended to reduce voltage drop) - I'm using 350A Class-T fuses on mine (available at finer marine supplyhouses near you) - these are the same as the one OrioN lists in the link above.

I have these installed in two places:

1. The cable going from the starting battery to the auxiliary battery bank.

2. The cable going from the auxiliary battery bank to the positive power distribution bus.

Both fuses are located in close proximity to the auxiliary battery bank (since it contains 500A of power ..... and I really don't want any inadvertent welding to be going on, should a failure/short to ground occur)

[jdcaples]

Fuses: The unsung heros that never go off duty and are always ready to die for the safety of other equipment.

Now that I think about it, there are a few people I'd like to see reincarnated as a 15 amp fuse on circuit that flirts with the frying threshold.

-Jon

[Aqua Puttana]

rlent is correct on fuses being sized to the cable, but you can up size the fuse by a bit (15% - 20%??) if needed for start-up current because in most vehicle situations the loads are rarely at 100% for extended periods. The fuse is to protect for catastrophic failures such as a short or grounded cable. That and for all intent and purpose most individual vehicles cables can be considered a single conductor in free air.

That said, rlent is also correct that bigger is better to avoid voltage drop which can be a real factor at 12 volts dc.

I agree with the unsung hero comment by Jon. Everybody always wants circuit breakers instead of fuses. Breakers are mechanical devices that can fail. Especially in an outdoor environment such as under the hood of a vehicle. When a fuse gets too hot it just opens. Of course that works pretty much 100% until some brainiac replaces a 15 amp fuse with a 30 amp at home because it was blowing too often. Then immediately you're 100% too high in protection. That is why breakers are better in homes. Operator error. Hope this does some good. AP

Originally Posted by rlent

As I understand it, your fusing should be sized for the cable you are using.

My cabling is double-ought (2/0) which is huge and probably overkill (but intended to reduce voltage drop) - I'm using 350A Class-T fuses on mine (available at finer marine supplyhouses near you) - these are the same as the one OrioN lists in the link above.

I have these installed in two places:

1. The cable going from the starting battery to the auxiliary battery bank.

2. The cable going from the auxiliary battery bank to the positive power distribution bus.

Both fuses are located in close proximity to the auxiliary battery bank (since it contains 500A of power ..... and I really don't want any inadvertent welding to be going on, should a failure/short to ground occur)

[jdcaples]

Originally Posted by Aqua Puttana

Everybody always wants circuit breakers instead of fuses. Breakers are mechanical devices that can fail.

A company called "Federal Pacific" made a product called the Electric Stab-Lok Panel. Marketed for home installations, its form factor was identical to the old fuse boxes that protected knob and tube wiring.

My home's building inspector told me that Stab-Lok breakers failed to trip 25% of the time, but the form factor - no lathe-n-plaster removal, no wall framing required to fit the new fangled circuit breaker boxes - was too compelling.

My Stab-Lok box was the first thing I removed from my home after buying it. I saw one, complete with OEM breakers in a recycle-your-home's-old-crap store. I pity the person that decides it'll fit nicely in that fuse panel's place. I've since read articles that state an 80% rate of "failure to trip."



-Jon

[Aqua Puttana]

Jon,
Good you got rid of that panel. That very design was one of the things that earned Federal Pacific the nickname "F*ckin' Pacific" among electricians in our area. Not to be outdone, Cutler-Hammer had their infamous "split bus" panels that overheated in the main connections.

Sorry for the continued hijack. Now back to our regularly scheduled programming. AP

Originally Posted by jdcaples

A company called "Federal Pacific" made a product called the Electric Stab-Lok Panel. Marketed for home installations, its form factor was identical to the old fuse boxes that protected knob and tube wiring.

My home's building inspector told me that Stab-Lok breakers failed to trip 25% of the time, but the form factor - no lathe-n-plaster removal, no wall framing required to fit the new fangled circuit breaker boxes - was too compelling.

My Stab-Lok box was the first thing I removed from my home after buying it. I saw one, complete with OEM breakers in a recycle-your-home's-old-crap store. I pity the person that decides it'll fit nicely in that fuse panel's place. I've since read articles that state an 80% rate of "failure to trip."



-Jon

[Expert Marine]

I agree that you should have closer to a 400A Class T fuse.

Personally I wire up inverters that are 2000 watts and up with 4/0 cable. The cables need to be as short as possible, and locate the Fuse near the battery. I also use a battery switch rated for 350A continuous inline on the positive wire, so the power to the inverter can be killed.
A good cable choice for the automotive market is welding cable, but I cant use it because it wont hold up in the marine environment.

I mostly use AGM batteries because they are sealed, and don't vent out explosive/corrosive gasses when charged or discharged.
Do not mount inverters next to wet cell batteries for a serious fire hazard exists.

Most inverters are not rated to be IGNITION PROTECTED.