I have just permanently mounted a 2000 watt continuous, 4000 watt surge, inverter in my truck. I want to install a fuse in the B+ line right at the battery. Nowhere on the unit or in the instructions is a fuse size given. Now I know 2000 watts at 110 volts is 18.18 amps. But can I apply that to the DC side? If I use 4000 watts that is 36.36 amps. Does that mean that I should use about a 40 amp fuse?
Just in case anybody asks, I am feeding the inverter with 1/0 welding cable with a run of about 9 feet. It is grounded to the frame and I added an extra ground wire at the front of the frame directly to where the negative wire bolts to the engine.
What kind of fuse is best? My resources here are somewhat limited. Have seen some hefty fuses and fuse holders at Radio Shack which I presume are use for speaker amps. Will they do?
Thanks in advance for your help.

 

Your calculation is correct. The Wattage is applied to the DC side as well as the AC side. You would require the 40 amp fuse at a minumum..

You could use circuit breakers for 50 amps instead of a fuse. They have resettable breakers for 50 amps at most Heavy truck outfitters for stuff like cranes and winches. Maybe try one of those places..

J-eh

 

The input power is supplied from +12VDC. 2000W supplied from 12Vdc = 167 Amps (It will actually be greater, I believe the 2000W is specified to be the output, therefore the input will be greater than 2000W, nothing is 100% efficient)

 

LiL Dog, never occured to to use a breaker. Wish there was an aircraft wrecking yard near me 'cuz they would be perfect. The only thing that concerns me using a breaker is that it is mounted next to the battery (in the engine compartment) and therefore will get wet and hot.
I want to fuse it as close to the battery as possible because the thought of that 1/0 cable grounding itself out gives me the horrors.

 

Woops.. I didn't actually do the calculation.... :-[

Boy is that dumb.... I should have paid more attention..

J-duh..

 

when you are fusing you are doing so to protect the wire

fuse within 18" of the battery

according to this chart 1/0 wire is good for 350 amps

I'd go with a 200 amp fuse or breaker myself


if you go to one of your local car stereo shops they sell water/wheather proof under hood fuses/fuse holders and circuit breakers such as this




your local rv supply place should carry them too I believe

 

Thanks. No such thing as RV supplies around here. In fact, no RV's unless it is the occasional one passing thru.
If it is confirmed that the fuse needs to be as high as 200 amps, then does anybody see a problem with using a common household cartridge fuse? Like the one that goes in the breaker box. It would be easy to make a support for the holder for a fuse like that.
I will check the stereo shops tomorrow and see what is available but I know whatever is available will be way over priced.

 

Mexstan, I too have a very large draw on my electrical system due to my stereo...(see details below). I have a #4 AWG power cable running directly from the drivers side battery to my amplifiers under the rear bench. I use an in-line fuse holder with a 60 amp fuse by Phoenix Gold....

http://www.phoenixgold.com/inlinexs.html

The holder is siliconized to the top of my electrical box right next to the battery. It stays dry and protected and can be easily unscrewed for fuse removal/replacement.

Good luck and thanks for the Fwd: messages.

Tom

 

Another place to look would be solar suppliers. Try here : http://www.backwoodssolar.com/Catalogpages2/wiring2.htm
They sell fuses and circuit breakers for high amperage D.C. equiptment. Their phone # is 208-263-4290 they can help you size your fuses.
Good luck

 

billg, solar suppliers? Down here? You gotta be joking. Good thought tho. Sure wish we had something like that here as I will be needing some solar stuff soon.
Actually, most stuff is available but things are very hard to track down. The annoying thing is the high prices, specially if it was made in China. Then there is the wierd thinking down here on what to stock. Sort of like company 'A' only sells bolts and screw but no nuts. You have to drive across town to find the company that sells the nuts. Very, very frustrating at times.

 

Oops wasn't paying attention to your location. They have an online store. They might be able to ship to you.

 

I have all but given up on having stuff shipped down to me. Snail mail arrives no problem but parcels often just disappear. Courier is expensive. Customs routinly charge 30% for everything. So I wait until go north or sometimes arrange for a shipment to go to a known address near the border for a friend to pick up. It's slow but it works.

 

billg is on the right path. Go look at the solar powered web sites/FAQ's; you can learn all you want about fuze types and sizes. They're all about low voltages, HIGH amps. Pay attention to DC stuff, not AC. If you can order things from the 'net, you're golden. I've got them bookmarked at work.

Don't forget to add the lengths of the red and black cables when figuring out cable guage requirements. 1/0 and 2/0 can get expensive and needed when running lotsa amps. That's why I didn't permenantly mount my 2kw inverter. I think I was thinking about a 300A or so fuze but that was a while back. There was a good thread on the other site WRT this topic.

Also go look at boat supply stores (they do have boats there don't they?). They'll carry a variety of fuze types/fuzes and capacities.

I'd fuze it and switch it. Keep that cable as protected as you can; if it ever shorts out, it'll behave like an arc welder, and fuze or not, it'll find a ground.

 

Thanks for all the info. I am inland and up in the mountains. (6000') No boats here either. Well, maybe a few outboard powered things for the lakes.
It is because I am well aware of how that 1/0 cable will behave if it goes to ground unprotected that I need a fuse. Maybe this is overkill, but for most of the run I encased that 1/0 cable in a heavy plastic 'duct'. They use that down here to bury in concrete walls as a conduit for the wiring.

 

Well contrary to what some folks think, living up here in the good ole USA has some bennies, huh?