ok so im trying to set up a tank for a bp that im going to get (yay!!) and i dont know whats wrong with the UTH's i have been using. i have a 20L and i got the appropriate size but when i turned it on and left it, a came back an hour later ans the glass wasnt even warm! i tried it without a thermostat first just because i was curious as to how hot they would get. i have tried two and the same thing happened both times. they were Zoo-Med Repti therm UTH's. i thought this was a good brand, so i am confused.

help!!

thanks