Typically, you'll know fairly fast if it's too tight. Degrees of too tight:
First the machine may groan a little and the pedal will get noticeably warm.
Then it may start to run without touching the pedal.
The hissing and crackling noises will start shortly after that and the pedal will be starting to get downright hot,
then... uh well I don't know because that's where I unplug them and take the pedal and run for the kitchen sink or stove so any resulting fire is contained.
Also, the pedal shouldn't generate heat when the pedal hasn't been pressed. That's one way I test them. I plug the pedal into the machine and the wall and leave it sit like that when I'm cleaning the machine. If it starts warming my toes when I touch it or a cat sidles up to it and cuddles up, I know it has to be adjusted.