Small lesson for all.
There is a technical difference between a "Safety (Disconnect) Switch" and a "Disconnect Switch". All Safety Disconnect Switches are disconnects, but not all disconnects are Safety Disconnects. A "Safety Disconnect Switch" is defined under UL98 and requires features not found in all of the cheap little rotary disconnects you can get from IEC manufacturers. The little rotary disconnects are UL508 listed as suplementary disconnects, meaning they can ONLY be used in circuits where there are other proitection devices up-stream that will limit the fault energy. Think of them as "isolation Disconects" as opposed to Safety Disconnects. One big issue is the action of the switch itself, hence the "One Armed bandit" side arm lever mechanism you see on most UL98 Safety Disconnect Switches. Other issues involve wihstand capability, opening under fault conditions, visible blades etc. etc. Bottom line is that you can use a Safety Disconnect Switch anywhewre, not so for a UL508 rotary disconnect.
All that said, Safety Disconnects come in standard sizes that relate to FUSE sizes. All fuses of a particular type will be the same physical size from .1-30A, then another size from 31-60A, another from 61-100A etc. etc. So 30A is always the smallest size they make, even in non-fused versions (because they really only make one switch and just don't add the clips). I find it hard to believe however that a 30A fused disconnect will have terminals that ONLY accept #10 wire; I think you read something wrong. That yould mean if you had a 5A fuse, you would still have to run 10ga wire? Preposterous. #14 is the smallest field wire, that's why the Sq. D switch, and every other switch I have ever seen, will accept down to 14ga wire, but no smaller. No legal need to go smaller.
