Here's the idea.
The "Humidistat" kicks on the fan when the humidity gets above 70%. I've got all that wired up well and good.
What I want is to add a 'switch override' (LEFT, diagram), so I can manually turn on the fan when needed, humidity be damned.
My thinking is to run a wire between the HOT (B) and LOAD, with a simple switch.
Normally the circuit will be completed only when the humidistat connects B to LOAD, and on to the fan, and out.

Will it blow a fuse, connecting the HOT on the Humidistat, directly to the LOAD?
I think it won't matter at all if its not above 70%, but wonder if it will still be OK if the hot current goes both ways, from B to load through the device, and also through the switch.
Since it still can run out to the fan, and on to the neutral wire.

I'd test it out, but I thought I'd ask first, because I don't want to bust the humidity detector.
Anyone?

 

Your override switch is shown as wired correctly and will do what you want.

Instead of a switch..... you could use a mechanical spring wound timer. They come in times from 15 minutes to hours. An hour would be a good time to use.
Tork 1 hour timer
Intermatic 1 hour timer