If the switch is rated for 30 Amps, and your lode is less than that, you are good. (wall plug in your house is 15A in most places, usually 20A in your kitchen and garage in most modern housing)
These switches are made (generaly) for single phase (120V circuit) switching, however this one is rated to 277V. So you could switch all the way up to a 240V heating element with it at 30Amps.
In general, it will depend on what the circuit breaker/fuse is rated for amp-wise. THe fuse/Curcuit Breaker should be rated to blow at an amperage lower than any of your devices... otherwise you switch will become the fuse....
The only thing to consider on this switch, is that you will be using it in a wet enviornment, so you could have issues if water works it's way into the swtich. If you position it so that it does not get wet, you should have no worries.
One last note, make sure you use the wire size rated for the amperage you will be carrying. 14 awg wire is not suitabe for 20A or greater loads, so use 12 awg or even 10awg if your amperage for the circuit requires it.
Good luck!