there are ones by finnex that i have tested that do for sure and the pro heat titanium heaters do as well( both use a seperate temp. controller) I have been running one of the finnex heaters for the past 3 years. there are others but like i said i wanna check once i go into work so i am not giving wrong info.hope this helps you believe me. I was only tryin to help by the way.
I would be interested to know as well....I need a couple of good heaters!!!