Whether the load types of the functional parts of the fuses to be merged are consistent, and only the electrical appliances with the same load type can share the fuses.
This should be easier to understand. If one is a resistive load using a fast-blow fuse, and the other is an inductive load using a slow-blow fuse, if the fuses of different load types are combined, the consequence will be a shared fuse. It is impossible to protect these two functional parts normally, and the fuse will also lose its function. Therefore, functional parts of different load types cannot share fuses.
The size of the load current of the functional parts of the fuse to be merged. Generally, a separate insurance is set for large currents, and the high and low current circuits (current difference above 5A) do not share a single insurance.
This point is actually also from the perspective of cost. If the fuse is combined with the functional parts with too large current difference, then correspondingly, the original small-diameter wire is equivalent to increasing the fuse, so it is necessary to increase the wire accordingly. Specifications to match the increase in fuse capacity will eventually lead to an increase in cost, and the common fuse will lose its meaning.