What are you talking about, a radiant heat panel or a ceramic heat emitter?

Radiant heat panels aren't designed for glass tanks and won't do much for one, and I have found that ceramic heat emitters get too hot. I would suggest that you get an infrared heat bulb. IR heat bulbs put out light that isn't visible to snakes so they can be left on 24/7.

Here is a good one: http://m.petsmart.com/mt/www.petsmar...3&lmdn=Reptile