Sander17, the high temperature is localized, and at the back of the switch away from combustibles. The dissipated power is probably no more than 15 watts at the highest, and the device is rated to 120. I would imagine it glows red hot at that rate! Any traditional rheostat will dissipate heat in this way. An extra point is that the heat sink is in the air flow of the fan, and is cooled by that. It operates happily for an hour with no localized excess heat. You make a good point, though. I made the mistake of holding the heatsink while testing the circuitry!
Nick
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