Kristalsdreamtrip
Well-known member
Can someone tell me what size circuit breaker I need for my little 400w inverter?
Size breaker for 400w inverter?
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highdesertranger
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What size wire feed the inverter? the fuse/breaker is to protect the wire not the device.
BTW in most cases fuses are better than breakers.
Make sure any breakers you use are rated for DC(Direct Current)
A lot of DC breakers are only meant to pass current in one direction
Most breakers are not designed to be use as a switch
Stay away from car audio stuff a lot of it is junk
Highdesertranger
BTW in most cases fuses are better than breakers.
Make sure any breakers you use are rated for DC(Direct Current)
A lot of DC breakers are only meant to pass current in one direction
Most breakers are not designed to be use as a switch
Stay away from car audio stuff a lot of it is junk
Highdesertranger
400W =Amps/12v so about 33Amp draw running, though it might have a surge of higher than that, possibly double (about 66A if surge is 800). Your documentation should tell you both these numbers. Then figure out how much of a run of wire you will be using to compensate for voltage drop, then size the fuse to the wire's capability. Don't use those silly little ciggy plugs unless you like the smell of melting plastic.
For example: 0-4' of 10AWG can handle up to 85A
Inverter under normal conditions shouldn't draw more than 70A
Fuse at 70A, that way if there's some sort of catastrophic failure at the inverter, the fuse will blow before the wire melts down.
If longer run than 4', go up a size in wire (down in number) to 8AWG for runs up to 10'
My inverter is 800W with a surge of 1200W. I have 6' of 4AWG protected by a 110A fuse.
For example: 0-4' of 10AWG can handle up to 85A
Inverter under normal conditions shouldn't draw more than 70A
Fuse at 70A, that way if there's some sort of catastrophic failure at the inverter, the fuse will blow before the wire melts down.
If longer run than 4', go up a size in wire (down in number) to 8AWG for runs up to 10'
My inverter is 800W with a surge of 1200W. I have 6' of 4AWG protected by a 110A fuse.
Kristalsdreamtrip
Well-known member
Thank you! I'm using 8awg for almost everything on my panel. It will only go a few inches
Kristalsdreamtrip
Well-known member
If I can ever figure out how to post a pic and how to resize it, I will post what I have so far. Ugh I'm horrible at all that. The instructions ions on here are very clear yet very complicated for my old brain I could probably ask my 13 year old autistic grandson to do it. He is a wiz! Haha
sneaks said:
I disagree with that.
A 400 watt inverter will be happy and safe with a 30 or 40 amp fuse. It will typically be used for laptop charging, power tool charging, TV watching, maybe the occasional miscellaneous other small items. Generally speaking, loads will typically be in the 50 to 200 watt range. It will not be expected to handle high surge loads, such as starting a motor, compressor, or microwave, like a 700 to 2000 watt inverter is typically used for.
If it blows a 40 amp fuse you are stressing the inverter and likely to damage it. In the case where an inverter does not have a built-in fuse, then the external fuse we add is also protecting the inverter, as well as the wires.
If the wire to this inverter will be rated to carry 70-100 amps, you may have 'oversized' the wire (which wont hurt anything, but don't put a 'ginormous' fuse on that large gauge wire, and then install this little inverter at the end without a properly sized fuse)
If you fuse a short run to the small inverter with a 70 amp fuse...and an overload, a short, or component failure occurs, a lot of burning and smoking can happen before that fuse blows.
As for posting resized images from a computer, I take a screenshot of the image while it is reduced in size in an image viewer, then I upload that screenshot image.
The screenshot is in a dot png format, also resulting in a smaller sized image file.
This process has a side effect of removing any private metadata from the original image.
The screenshot is in a dot png format, also resulting in a smaller sized image file.
This process has a side effect of removing any private metadata from the original image.
ldsreliance
Well-known member
It depends on what you are protecting. If you just want to protect the wire and prevent a fire, a 70A fuse is the ticket (assuming it is sized properly for that gauge wire and length of run). If you want to protect the inverter then that would not be a good size.
Any inverter worth beans is going to have a fuse on it, though, so protecting the inverter probably is not necessary.
Any inverter worth beans is going to have a fuse on it, though, so protecting the inverter probably is not necessary.
ldsreliance said:
Many of the larger inverters (above 500 watts to about 3000 watts) do not have a user-replaceable fuse. Some of the mid-sized (like the OP 400 watt) inverters do have a fuse, some don't.
And yes, most if not all of the inverters in the smaller capacities (75 watts to around 300 watts or so) DO have fuses either in the unit itself or in the cigarette lighter power plug if they use that type of connector.
Since the OP asked, my assumption is that there is no fuse on the unit itself. But there might be, and in that case the inline fuse could probably safely be upgraded to, say, 50 amps or even more, depending on wire size. In fact, if the OP's 400 watt inverter has a built-in fuse, say, 30 to 50 amps, then it is reasonable to install an actual DC circuit breaker (75-100 amps) in place of an inline fuse, again, assuming sufficient wire gauge.
ldsreliance
Well-known member
I agree. Like I said, it just depends on what you are trying to protect. I think newbies just think that they need a fuse, any fuse, in there and they are good to go. But it needs to be properly rated, properly sized, and you have to have a purpose in mind for it.
I looked up the top 10 results for 400w inverters in Google. Check the specs. 400W is continuous. Most will surge to 600-800w, and we have no idea what she is going to connect to this inverter. It could be something minor or it could be a continuous max draw with random spikes. My 800W will hit 90A for a half a second when tossing the switch, then will settle down, and that's with nothing connected to it. I have a shunt on that circuit. Yes, my inverter has dual fuses 100A from the factory, one on the feed, on on the earth. Neither have ever blow, but when I dropped a butter knife and it landed just right on the small exposed part of the lugs not covered with the nuts, it blew my fuse at the battery instead of welding it across the terminals and melting down my rig.
It isn't any different than a compressor fridge that hits 2-3x the draw for a few seconds when it kicks on. If you don't mind replacing the fuse every couple of times, then go for it. I'd rather not. Size the wire to be safe for the max draw of the unit, then size the fuse a little smaller to protect the wire, as close to the battery as reasonable. I'm not saying run 00g and a massive 300A fuse, but staying within the manufacturer's parameters for the device. Decide what you feel is the acceptable risk.
It isn't any different than a compressor fridge that hits 2-3x the draw for a few seconds when it kicks on. If you don't mind replacing the fuse every couple of times, then go for it. I'd rather not. Size the wire to be safe for the max draw of the unit, then size the fuse a little smaller to protect the wire, as close to the battery as reasonable. I'm not saying run 00g and a massive 300A fuse, but staying within the manufacturer's parameters for the device. Decide what you feel is the acceptable risk.
^^^ What he said. You guys, I tell you just wire it with the gage recommended or what came with it if it will reach without extending it. Most small inverters won't have room where the terminal attaches for anything bigger than 8 gage. My 350 watt pure sine wave inverter came with 12" long 10 gage wires with clips. You stated it would be a short run of just inches (be sure your inverter is isolated from the possible fumes from the battery if using lead acid batteries). Try to find a fuse holder that has an eye terminal so you can attach it directly to the accessory bolt on the military type battery terminal and attach your positive wire to the other side of the fuse holder. The fuse holder will hold normal spade fuses up to 40 amps. What I did was install a 25 amp fuse and it worked fine for the small loads I had like a charger for my computer or GPS unit. The wires after several hours never got hot and the fuse held. If the fuse had blown I would have put in a 30 amp fuse and checked the wires again after several hours. This is what you do if you don't know what you are dealing with. It is possible to calculate using the charts and tables as well as the information on the inverter to determine the maximum current limits based on the length of the wires and the loads the inverter was designed to carry and you should do that but until you furnish that info to us no one can tell you for sure what you need. People here are a very good at looking up and finding specs but just are not very good guessers. Pictures would really help.
It comes down to this:
If you start with a fuse rating that is purposely too 'small'...you will blow that one and you might go to the next higher rated fuse. Repeat if necessary, UP TO THE SAFE LIMIT of the wires or the inverter instructions. So you blew a couple of fuses and had to throw them away. Meh.
But on the other hand, if you install too large of a fuse ('large' meaning higher ratings that you should use) and something really bad happens, you might be explaining that to the first responders flooding the smoking remains of your van.
So, I play it safe and purposely derate small and midsize inverter fuses.
If you start with a fuse rating that is purposely too 'small'...you will blow that one and you might go to the next higher rated fuse. Repeat if necessary, UP TO THE SAFE LIMIT of the wires or the inverter instructions. So you blew a couple of fuses and had to throw them away. Meh.
But on the other hand, if you install too large of a fuse ('large' meaning higher ratings that you should use) and something really bad happens, you might be explaining that to the first responders flooding the smoking remains of your van.
So, I play it safe and purposely derate small and midsize inverter fuses.
Kristalsdreamtrip
Well-known member
That makes sense. I'm a newbie but I'm trying not to be "that" newbie, haha. I put that 400w inverter somewhere. I seem to have misplaced it but I will find it. I don't know if it is fused or not. I'm sure I don't have instructions anymore but I will download them when I find it. I'm using 8awg everywhere for very short distances on a board. This is the guy I watch mostly
There is a type of extra non-conductive tape or putty (I can't remember), that can be used to cover and protect any exposed terminals/connectors/wires so they don't risk getting touched by anything metal. I want to get some but not sure what it's called exactly. Does anyone know?
Every once in a while I hear a phrase that sticks in my head. I'm not sure where but one is "you don't have to buy meters/fuses. You should only meter/fuse the things you care about" or something close to that.
There is a type of extra non-conductive tape or putty (I can't remember), that can be used to cover and protect any exposed terminals/connectors/wires so they don't risk getting touched by anything metal. I want to get some but not sure what it's called exactly. Does anyone know?
Every once in a while I hear a phrase that sticks in my head. I'm not sure where but one is "you don't have to buy meters/fuses. You should only meter/fuse the things you care about" or something close to that.
Kristalsdreamtrip
Well-known member
Kristalsdreamtrip
Well-known member
I worked! Thanks for the help, the screenshot method worked, yay!
It would help to also have a picture of the inverter, there should be a tag or label to give us an idea if it is fused. If possible a picture of what you plan to run with the inverter as well. Your battery specs would be helpful also. Just some concerns from the picture, like bungee cords and uninsulated battery connectors should be reconsidered. I would try to arrange the batteries to where all negative terminals were in a line and all positive terminals were in a line, it is awful easy to have a short if they are positioned next to each other like that which is never a good thing. If you want take a picture of the back side of the board as well, we will be glad to make suggestions.
PlethoraOfGuns
Well-known member
400w, draws 33amps, few inches of wire between inverter and battery, 8awg with 40amp fuse, done, safe, will work. If it doesn't, then you'll safely know and those few inches of wire are not a big deal to upgrade.
Kristalsdreamtrip
Well-known member
I will do all that in pic now that I can! Stay tuned. Thanks so much
Kristalsdreamtrip
Well-known member
This is the newest of some 30+ drawings and pics of some of the exact equipment I'm using. I still cannot find my 400w inverter so I was gifted this one I'm showing. It's only 300w but should be plenty enough for my needs, I think. I'm hoping this shows a better battery arrangement as I think you were describing. Also, the bungee cords are just temps until I work this out right. I have regular battery straps and covers for much of the wire connections. As you can see, I am still not sure what to do with which meters. I have 4 different types and I'm picturing them. I greatly appreciate all the feedback and advice I can get. I'll list all the appliances I'll possibly be using tomorrow. My daughter did buy me the Kuppet compressor fridge so I'm happily selling my igloo cooler on facebook. I hope all these pictures work
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https://www.dropbox.com/s/dfq0h8x2xwv12ys/screenshot_20210614-125012.png?dl=0
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https://www.dropbox.com/s/jii4mfn19y16w13/screenshot_20210614-124836.png?dl=0
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