Many of us love to run our pedals at higher voltages. However, some pedals simply won't work properly, or at all, with the wrong voltage. Here's an over-exaggerated video of what happens when you run 18v to the Tumnus, Tumnus Deluxe, or other pedals that have a charge pump internally which boosts the voltage.
Also, some of you may wonder why I toasted a perfectly good pedal. Two things with that:
1. It was actually 2 pedals. Multiple camera angles and all that.
2. Both pedals were already screwed up from someone running 18v through it.