I would use a breaker, rather than a fuse. The reason is that the breaker can also be used as your disconnect switch. The purpose of the breaker is to protect the wire, so normal loads are irrelevant. You need to look up the ampacity rating of your particular 2AWG wire. If it is rated for 90C then the ampacity is 130 amps. So the maximum breaker rating would be 130 amps.

Because you might not easily find a 130 amp breaker, it would be good to know the minimum breaker size as well. Now is when you can look at normal loads. 3000 watts divided by 24 volts equals 125 amps. So you don't have a lot of leeway on breaker size -- 125-130 amps.

There is no reason you cannot go larger with your wire. In fact, you might want to do that in order to minimize voltage drop. If instead you used 1/0 rated for 90C your ampacity would increase to 170 amps, and you could then use a breaker rated at 170 amps or less, and you would have less voltage drop.

That is the reasoning behind choosing breaker size, and those are some examples of your options. If it were me, I would probably go with 1/0 because I do not like to cut corners on fat wires. But there is absolutely nothing wrong with using 2 AWG as long as your breaker is properly sized.

Link to ampacity chart
Link to voltage drop chart