I wanted to add a fuse protection to a circuit. The device runs on 110V and draws close to 400mA. Checked my collection and found these (picture added below)vintage 1/2A 250V fuses collection. Are these fuses only meant for 220V circuits? Just wanted to clarify if its safe to use it in a 110V circuit or should I get another 1/2A fuse made for 115V specifically?

 

You are good. The voltage rating of a fuse is the max voltage you want them to break.

Obviously if the fuse cas break (open) at 250 volts it will also open for 110v.

 

The fuse rating is the maximum voltage, not the operating voltage, so using the 250V fuse in a 120V circuit gives you a good operating margin.

Conversely, you never want to use a fuse with a lower voltage rating than the operating voltage.

 

Thanks guys. So I'm good to go with it