Breaker fight

[Rachel821]

Hi all,

So I have a solar system and recently upgraded my inverter and batteries. AGM (300ah) + ************/cheap inverter (3000w) to 400ah lithium batteries + nice voltworks pure sine inverter (3000w). Before the switch, there was a 300ah breaker installed between the two and it would trip anytime I turned on my 7gl hot water heater, even with the new equipment and bigger battery bank - the breaker still tripped. After doing a bit more research, I read that you don't necessarily need a breaker between these pieces of equipment, the inverter is built with adequate protections. We were also using a 5g wire which clearly wasn't big enough.

SO after the advice of voltworks, we replaced the wire with a 0 gauge, took out the breaker and everything has been running great since! Until I had a few people on social media tell me to put a breaker back in but increase to 400ah. I'm so sick of the conflicting information lol so I hoped to get more experienced opinions here. Is my equipment/tiny home safe? Or should I add some protections between my batteries and inverter?

 

[plh]

assuming it is a 12V system? 3000W inverter draws +/- 250A - probably more when the powered devise kicks in (in rush current). Plus losses at every crimp, connection, junction etc. Breakers protect the wires and prevent fires. 0 gauge is too small as well. Rated for 150A. Recommended is 0000 gauge according to most manufactures.

 

[DiploStrat]

Conventional wisdom is a breaker/fuse if run is more than about 18 inches. Size to protect the wire. (You can size lower for the load, if you wish, but never higher.)

 

[Rachel821]

assuming it is a 12V system? 3000W inverter draws +/- 250A - probably more when the powered devise kicks in (in rush current). Plus losses at every crimp, connection, junction etc. Breakers protect the wires and prevent fires. 0 gauge is too small as well. Rated for 150A. Recommended is 0000 gauge according to most manufactures.

If my wire is 4/0 and I just made a typo, I should be fine?

 

[DiploStrat]

Sizing the wire for the load is essential, but breakers protect you when the insulation wears through and the cable shorts. You don't want 20 foot arc welder under your truck. Hence a breaker within 18 inches of a power source.

 

[Rachel821]

The wire reads 0AWG but the thickness is of a 4/0 which is confusing. Diplostrat - I have no idea what you just said lol

 

[plh]

If my wire is 4/0 and I just made a typo, I should be fine?

300 amp breaker located within 18" of your battery

 

[carleton]

Rachel, 12v power is complicated and hard to learn, but if you stick with it it'll make you a better vanlifer: you can diagnose things on the road and fix as needed.

" Sizing the wire for the load is essential, but breakers protect you when the insulation wears through and the cable shorts. You don't want 20 foot arc welder under your truck. Hence a breaker within 18 inches of a power source. "
-Basically, you want a breaker of some kind close to your battery (in between your battery & inverter). Vans move and over many miles your cable can wear a hole, and without a breaker it can start a fire/etc inside your vehicle.

-W=amps X volts. So, 3000w Inverter/12v system= 250amps.
So that's where PLH is saying a 300Amp breaker is probably sufficient.

-Wire size: I always just use an online calculator, like this Online Wire Size Calculators & Tables
4/0 is what it recommended. But if you have a long distance voltage drop may be an issue.

Overall, all of us would need to know much more about your system to figure out what is going on, either a diagram or photos, and information about what water heater you have installed. Distances are also important: if you have a long run from your batteries to your inverter, that can also throw things off (voltage drop).

 

[jonyjoe101]

something else to look at is if the circuit breaker is not a true 300a circuit breaker. I had some 30a breakers that kept breaking at 22 amps. I had to replace with better quality breakers that could handle the actual amps.
I had to use a dc wattmeter to see where the breakers were breaking.

 

[OllieChristopher]

There are circumstances where its reasonably safe to omit a circuitbreaker. Without seeing precise detail of your setup, I wont say if its ok or not.
Regardless, if its not really needed, its cheap insurance to have and a handy method to disconnect the system for service or something.

This, and I will add in ALL circumstances it's better to be fused and have a disconnect. I would not ever use any kind of circuit breaker in a 12 volt system. Circuit breakers can fail. I'm all for the redundancy of fuses when building out a mobile system in a vehicle. I fuse for the wire and and additional (smaller fuse) for saving the component. And of course you want the fuse to blow at a lower rating than the wire.

Look at any fleet of flammable hazmat trucks and the smart carriers ditch the factory breakers and install fuses for safety.