Changing from 12v to 24v circuit

Hey guys, I need some help. I’m changing a 12v circuit to 24v. I’ll include a fuse for safety but I’m not sure if a 20 amp fuse would do or if I need to go higher.
Thanks so much for your help
While Phil's point is fairly direct, it would help in us knowing why the change
to 24V (assuming nominal battery voltage supply).
In many cases it is more economical to run 12v systems through a 24/12v converter
especially if 24v kit is not available.

In doing that you would look at each device to work out power consumption,
giving you the supply current and a size of fuse to consider.
R = V/I....assuming the load stays the same then solve
current should come down....just measure the current or like David says look at the rated current on the device/s
usually, the manufacture gives a recommendation of blow...slow blow...rating