Circuit breakers for inverters

[garfield28]

Hi all,

Been a while, I hope everyone is having a great day!

In have a question about inverters, I just installed a 1500W inverter in mine, and it seems to work fine for about 40 seconds or so and then it trips. I have a 150amp circuit breaker that I bought off eBay, and it keeps tripping, and when I feel the cable at the end that connects to the breaker it is really warm, but the end that is coming out of the inverter is fine. I have 35mm sq cable so it is way thick enough, I believe maybe the breaker is just garbage but not 100% sure.

Is a breaker or a fuse better do most think?

Thanks
Geoff

 

[Boots in Action]

Hi all,

Been a while, I hope everyone is having a great day!

In have a question about inverters, I just installed a 1500W inverter in mine, and it seems to work fine for about 40 seconds or so and then it trips. I have a 150amp circuit breaker that I bought off eBay, and it keeps tripping, and when I feel the cable at the end that connects to the breaker it is really warm, but the end that is coming out of the inverter is fine. I have 35mm sq cable so it is way thick enough, I believe maybe the breaker is just garbage but not 100% sure.

Is a breaker or a fuse better do most think?

Thanks
Geoff

From your description, and the fact that the INPUT connection is feeling warm/hot. I believe that the connection may be a high resistance point. Remember, an inverter pulls a lot of (12 volt) current to boost voltage up to 240 volts at whatever the AC current is required. If you want to run your toaster (rated at 1200 watts) that will draw around 120 amps at 12 volt from battery.. If the wiring is not good enough or the electrical connection/s not perfect, that will generate a "hot/warm" junction point. I would ensure that was not the problem firstly before moving to other areas that could cause a problem, Maybe check the rated 240v wattage of items being connected. Anything rated higher than 1300 watts is pushing the limits of a 1500 watt inverter IMHO. Breakers do get warm and weaken before tripping out and resetting but eventually fail to carry the full rated current, but fuses blow and need to be replaced each time current is exceeded

 

[jazzeddie1234]

Ebay breakers are pretty unpredictable at high current in my experience. They use heat (resistance across the contacts) to bend a bi metalic strip so warmth is fairly normal. However a poor termination right on the bolt connections will also cause heat and that trips the breaker early. The design of the bolt is very average and can be very difficult to get a good surface contact.
I bought several ratings on ebay and they tripped at very random currents - always below fortunately but very frustrating

In the end I changed the inverter to more reliable ($10 for 5 plus holder on ebay) ANL fuses. Maybe also get some 200amp ones in case the 150s blow on full inverter load.

 

[Drover]

2 B&S would be minimum as its about the max draw of the invertor, I think 1B&S gives the cable better protection, the breaker is to protect the cable from melt down ................... To test your breaker start of with a small load like a battery charger or light then progress up to the heavier load, you will find that things like a coffee machine will pull a stonking great draw at first and this will possible trip your invertor, ideally your load should only be about 2/3rds of the invertor capacity ...... ............. Have used a few of the Ebay breakers and no problems to date but an ANL fuse that @jazzeddie1234 suggested I think is a better option ............ of course assuming your using proper lugs on the cable and not dinky crimp jobs .....

You also may be just drawing too much, if its doing it with no load then the breaker is most certainly stuffed.

My 2 kva Genny will give a groan if I fire up the coffee pod machine at first, once its going it settles back down but that first draw of power is a biggy...

 

[garfield28]

Thanks for the reply men.

I have just watched the install process on the kings YouTube channel and I have just realised I have stuffed up, I have the circuit breaker closer to the inverter and it is meant to be closer to the battery, not sure that would be causing the problem you think ? I'm going to change it around though.

I'm using 35mm square cable as i have had to run about a meter or just over, so figured thicker cable would be better.

I think I'll go with the fuse too, because you're right about getting good contact, the studs on the breaker are 6mm and anything that is 150amp rated you would think would require thicker cable so why are the studs so bloody thin?

Thanks

 

[jazzeddie1234]

assuming your using proper lugs on the cable and not dinky crimp jobs

Yes this is an important point. I'm pretty experienced in wiring but 150amps was quick to show up a small resistance in my lug terminations. Takes a high powered soldering iron to do it well

 

[garfield28]

Yes this is an important point. I'm pretty experienced in wiring but 150amps was quick to show up a small resistance in my lug terminations. Takes a high powered soldering iron to do it well

So you recommend a ANL fuses?

I'm not sure that breaker is the best as I did buy it from eBay, but I like the fact that with a breaker you can just reset it, if I'm away somewhere would be easier than trying to find or replace a fuse if it did burn it out

 

[jazzeddie1234]

So you recommend a ANL fuses

Yes for an inverter. Two reasons - the inverter fuse is often the largest in the circuit and acts as the master fuse, an inverter blowing a properly rated fuse is likely to need more than a simple breaker reset.
All my 10 to 50 amp circuits (including solar) have breakers that can act as an off switch. Very handy. Below 10 amps I stick with common garden blade fuses as I want them fast acting.

Just remember that if the ANL is both master and inverter fuse then add on the extra demand when the inverter is at full go - eg say 150amps plus another 50 =200amps.

This is mine with a slightly under size fuse but I never use 2kw

 

[Drover]

The info that rings bells with me is you are wanting to draw 150a over a metre with 35m square cable which is roughly 2 B&S, now that doesn't give a lot of room to play with if your trying to draw near its max loading somewhere between 160/180a depending on the data sheet, I would be looking at 1 B&S really, 210 odd amp rating so a bit of leeway, important if your going to be running the invertor at near max load that is .....

The fuse/breaker should be near the battery then the fuse will trip before the wiring melts BUT you should do an audit on your power needs and really if your max draw wants 1kw then the minimum size inverter I would use would be a 1.5, if its more then a bigger invertor, you certainly don't want to be running near max nor trying to run a toaster and coffee machine at the same time ..................... A soldered lug like this is the best way to go.

 

[garfield28]

Yes for an inverter. Two reasons - the inverter fuse is often the largest in the circuit and acts as the master fuse, an inverter blowing a properly rated fuse is likely to need more than a simple breaker reset.
All my 10 to 50 amp circuits (including solar) have breakers that can act as an off switch. Very handy. Below 10 amps I stick with common garden blade fuses as I want them fast acting.

Just remember that if the ANL is both master and inverter fuse then add on the extra demand when the inverter is at full go - eg say 150amps plus another 50 =200amps.
View attachment 69612This is mine with a slightly under size fuse but I never use 2kw

Thanks for the info Jazza,

The way I've set mine up is I have fuse box connected to a 50amp breaker for all of my smaller 12V accessories, and the inverter I was running the 35mm positive cable directly from the inverter with the breaker to the battery. As I say though the cable on the breaker post was quite warm, not sure if that is because I have a short run of cable from the inverter to the breaker, and a longer run of cable from the breaker to the actual battery... I have since read that the breaker or fuse needs to be as close to the power source as possible, which now intended to do and I will replace the breaker with the ANL fuse I just hope it doesn't go burning out all of the time and I have to replace them when I am away remotely.

The info that rings bells with me is you are wanting to draw 150a over a metre with 35m square cable which is roughly 2 B&S, now that doesn't give a lot of room to play with if your trying to draw near its max loading somewhere between 160/180a depending on the data sheet, I would be looking at 1 B&S really, 210 odd amp rating so a bit of leeway, important if your going to be running the invertor at near max load that is .....

The fuse/breaker should be near the battery then the fuse will trip before the wiring melts BUT you should do an audit on your power needs and really if your max draw wants 1kw then the minimum size inverter I would use would be a 1.5, if its more then a bigger invertor, you certainly don't want to be running near max nor trying to run a toaster and coffee machine at the same time ..................... A soldered lug like this is the best way to go.
View attachment 69613

Thanks Drover

What is 1 B&S in sq mm?

The cable that Kings supplied with the invert is way smaller than the one I replaced it with so I would have thought 35mm sq was overkill but, looks like I am wrong.

I could make the cable shorter from the battery to the inverter but it just won't look as pretty, should that be something I should look at doing so that I have a shorter cable run?

Also, I have used those lugs you suggested I should use Drover, but the hole on the one that is connected to the breaker was slightly oversized because the damn breaker studs are only 6mm, so I used about an 8mm lug and added a flat washer underneath and over the top to try and make it better contact, actually do you think that could be an issue also?

Thanks

 

[Boots in Action]

Thanks for the info Jazza,

The way I've set mine up is I have fuse box connected to a 50amp breaker for all of my smaller 12V accessories, and the inverter I was running the 35mm positive cable directly from the inverter with the breaker to the battery. As I say though the cable on the breaker post was quite warm, not sure if that is because I have a short run of cable from the inverter to the breaker, and a longer run of cable from the breaker to the actual battery... I have since read that the breaker or fuse needs to be as close to the power source as possible, which now intended to do and I will replace the breaker with the ANL fuse I just hope it doesn't go burning out all of the time and I have to replace them when I am away remotely.




Thanks Drover

What is 1 B&S in sq mm?

The cable that Kings supplied with the invert is way smaller than the one I replaced it with so I would have thought 35mm sq was overkill but, looks like I am wrong.

I could make the cable shorter from the battery to the inverter but it just won't look as pretty, should that be something I should look at doing so that I have a shorter cable run?

Also, I have used those lugs you suggested I should use Drover, but the hole on the one that is connected to the breaker was slightly oversized because the damn breaker studs are only 6mm, so I used about an 8mm lug and added a flat washer underneath and over the top to try and make it better contact, actually do you think that could be an issue also?

Thanks

@garfield28 , the issue with placing a good washer (brass?) under and on top of connector lug is that there is always some sort of air gap, and the contact point/s between lug and stud is still not 100%. To transfer high current (amps) on to contact points fully, you may need to modify terminal/s so that there is more contact made. Even drilling out a bigger eye on a smaller sized lug as long as it can accept the heavy wire and has substantial metal contact area.

 

[garfield28]

Thanks Boots

I'm thinking this could be part of my issue. I should add that the washers I used are Stainless steel too, is that a problem?

Think I'll just get the ANL fuse and connect it closer to the battery than where it is now.

 

[Drover]

1 B&S is about 39mm square, 210-210amp, so a hefty bit of lead .............. I'd do the fuse bit first and then see what happens but again even moving the breaker/fuse close to battery may not stop the terminal getting hot, if it still does then it points to a heavy load so you may be putting too much on the unit............ @Boots in Action idea about drilling out the lug hole is spot on also the invertor cable should be the first lug on the battery terminal, should sit flat on the face of the terminal so it gets the best contact and first dib at power ........... there are probably tech terms to use but eh !!!!!! ....................... ideally then you should only have one other set that goes to a bus bar or similar distribution terminal, the less hanging off a battery the better.................

What are you trying to run from the inverter anyway ???????

My Invertor while only 600w (800w ?) is only for charging laptops, drill batteries etc the cables looked a bit on the small side to me but since my unit doesn't get anywhere near half throttle its not a biggy ...................... I can run it and my solar panels supply the power as the battery doesn't move off 100% .......

 

[garfield28]

I was testing on a induction cooktop but running at 1200W

 

[jazzeddie1234]

We use our 1.5kw (150amp ish) microwave in short bursts a fair bit. And the toaster most mornings. And a hair dryer (not for me...) . My objective is to have the same experience in a free camp as a camp ground. Then we don't have to adjust our meals too much. I don't have the room to carry a bbq so it's mostly electric and gas oven...or camp fire

The inverter came with twin cables between lugs and I cut then as short as possible. Washers are not as good as it adds another junction for all that current to cross. I would try for a really good flat between the lug and bolt. The ebay breakers often have the flat slightly recessed for some crazy reason so I have seen people file the body down to expose the full surface

 

[Drover]

I was testing on a induction cook top but running at 1200W

Did a bit of 101 on them for camping, well 1200w would be about the max setting for a 1500w inverter thats for sure, bit power hungry if doing a long cook and they draw the power in cycles so not a continuous draw down like a coffee machine but still a big chunk from the battery but with decent solar set up be good I think, though I would want plenty of storage if using one for evening meal ......................

If 1200w was the max setting I would prefer a 2000w inverter then the unit doesn't have to peddle as hard .................. I won't mention these cook tops to a certain someone as she might get ideas, they want me to fit one in the house so not going to let on she could have one for van, then again when I mention a new inverter and some more lithiums she will change her mind .......... though she does like gas cooking anyway....

We don't carry a barbie anymore since getting the Jeep and no great change in style from park to bush really, we do most of our cooking on a small burner outside, change electric kettle for gas kettle though micro wave would be nice sometimes , if desperate could just fire up the Honda..........

Old folk so gone are the days of big cook ups sadly.... 2 bangers or small steak is about it with rabbit tucker, quite sad really...............