Off grid inverter AC out breaker

[ns31]

Hi all, just wondering what form of breaker/protection people use on the AC output cables that run from their inverters to the CU/board?

I'm thinking... the AC out of inverters is usually rated up to 50 amps, but if for example, in your board you had two rcbo's rated at 32a, then running both of these could overload the cable (depending on the gauge) and the inverter?

In houses there's a fuse on the cable that feeds the mains supply, so surely the cable from the inverters AC out needs a fused connection as it's effectively a new mains supply for your off grid board.

Also, do inverters themselves generally have an auto cut off if the ac output is overloaded? If so, the cable itself wouldn’t need protection, providing it was the correct gauge to handle the load. Thanks

 

[Rednecktek]

Hi all, just wondering what form of breaker/protection people use on the AC output cables that run from their inverters to the CU/board?

I'm thinking... the AC out of inverters is usually rated up to 50 amps, but if for example, in your board you had two rcbo's rated at 32a, then running both of these could overload the cable (depending on the gauge) and the inverter?

It really depends on the size of the inverter, but a lot of times you just bring it to a breaker in the box, maybe a jumper on a double breaker to feed both legs of the panel. Wire is usually calculated for the amperage being sent over. Other times people will install a breaker just off the inverter and then takes the wires right to the main lugs in the panel. One way or another there's a breaker involved.

In houses there's a fuse on the cable that feeds the mains supply, so surely the cable from the inverters AC out needs a fused connection as it's effectively a new mains supply for your off grid board.

There is?? Every panel I've ever seen has a breaker bolted to the main bus bars, but I've never seen a fuse on the PUD drop.

Also, do inverters themselves generally have an auto cut off if the ac output is overloaded? If so, the cable itself wouldn’t need protection, providing it was the correct gauge to handle the load. Thanks

Yes, when you start overloading an inverter it usually has an alarm or self cut-off to protect itself.

 

[ns31]

Thanks, do people run their AC out to a mains switch in the board? Or direct to an RCD?

 

[Rednecktek]

It seems to be about 50/50 whether people take it through a separate breaker to the main lugs in the panel OR run them to a double slot breaker right inside the panel. Best practice would be to use a separate breaker close to the inverter so it protects the wires between the inverter and the breaker panel.