A fuse and holder from auto parts store is fine. On closer inspection you'll see they are usually rated 250 volts.

If the zone board already has a fuse and that’s all the transformer runs, then you might consider a properly sized fuse on the transformer’s primary side winding.

IMPO

SR

Thanks Klem1, I will pick on up today.

fsq4cw - I did not see any fuse on the zone board at all. When you say put a fuse on the primary side you are saying to also fuse the transformer input power source correct?

That would be the best way to protect the transformer itself. Fusing after the transformer secondary winding will protect everything down stream after the transformer but not the transformer itself, unless it's otherwise protected. You can fuse both transformer windings (primary & secondary) but the questions become what value fuse (amperage) and whether to use fast blow, slow blow or time delay fuses of the correct values. Voltage does not matter, you can use 250v.

IMPO

SR