Sanity check please on circuit breaker

[DaGoose13]

So, I have a Growatt 24v 3000tl lvm inverter (https://watts247.com/product/spf-3000tl-lvm-24p/) and I'm trying to figure out what circuit breaker I would need.

I was looking at this https://www.amazon.com/dp/B07B8BX3P2/ref=twister_B07DF7RSDV as I shouldn't be able to get more than 80amps from the inverter.

This is the chart they put in for the cutoff. Will this work or do I need something bigger? Thanks.

 

[DaGoose13]

One thing that I forgot in the original post. These are the batteries that I'm using https://www.amazon.com/gp/product/B08K7HZ6KZ

They should be able to handle 200 amps in.

 

[rmaddy]

What will this breaker be used for? Is it intended to go between the battery and the all-in-one or act as a PV disconnect between the solar panels and the all-in-one?

Between the battery and the all-in-one you need a 200A Class-T fuse.

For a PV disconnect you should use a DC rated 2-pole breaker that can fully handle the max PV input voltage of the all-in-one.

 

[DaGoose13]

It's intended to go between the battery and all-in-one. Would a lower rated Class-T fuse work, since I won't be able to push or pull that much amperage from the battery with that all-in-one?

So, for a PV disconnect, I would want something like 150v for the current all-in-one, since I think it's rated up to 145v?

 

[rmaddy]

It's intended to go between the battery and all-in-one. Would a lower rated Class-T fuse work, since I won't be able to push or pull that much amperage from the battery with that all-in-one?

It's a 24V 3000W inverter. That can result in up to 150A being pulled from the batteries. For that you need at least 1AWG wire. 1/0AWG would be even better. Then you need to protect the wire with a 200A fuse. Since you have a 24V LiFePO₄ battery bank the fuse should be a Class T fuse. You can probably get away with a 175A fuse but 200A is better.

So, for a PV disconnect, I would want something like 150v for the current all-in-one, since I think it's rated up to 145v?

A breaker rated for only 150V might be cutting it too close. No sense stressing the breaker so close to its max voltage rating. But then again, if your solar panel array will max out at say 120V then such a breaker would be fine. Post a link to whatever breaker you think you might get.

 

[chess-equality]

It's a 24V 3000W inverter. That can result in up to 150A being pulled from the batteries. For that you need at least 1AWG wire. 1/0AWG would be even better. Then you need to protect the wire with a 200A fuse. Since you have a 24V LiFePO₄ battery bank the fuse should be a Class T fuse. You can probably get away with a 175A fuse but 200A is better.

The general rule is 125% (or was it 120%?) of the amps rating of the device / wire.

But what if you do not plan to use the maximum 3kw load?

It's intended to go between the battery and all-in-one. Would a lower rated Class-T fuse work, since I won't be able to push or pull that much amperage from the battery with that all-in-one?

 

[rmaddy]

The general rule is 125% (or was it 120%?) of the amps rating of the device / wire.

Actually no. You determine the max amperage being pulled from the batteries as inverter max wattage / battery low voltage / 85% efficiency. That gives the max current so you can choose the correct wire size. Then 125% times that value gives you the fuse size. So 150A for the wire size (1AWG or 1/0AWG) and then 150A x 125% = 187A fuse. Round up to 200A.

But what if you do not plan to use the maximum 3kw load?

It's better to wire and fuse for the hardware. You may not plan on using all 3kW but why limit the hardware? You may want to take full advantage or maybe a future user will. Cheaper and easier to do it right the first time.