ECN Forum Forums General Topics of the Trade General Discussion Area Protecting old fuse panels with 20amps?

When was it practice to upgrade service, and protect old 120volt subpanel feeders with 20amp 1 pole, and leave 20-25 amp fuses in the screw shells, some with 14ga. wire. And that was Ok? I've seen dozens of places in the SF bay area? shouldn't I put in 15 type s fuses?