A 100 watt CHE puts out just about as much heat as a 100 watt light bulb,
it just doesn't produce any actual light. So the CHE doesn't really have a
minimum distance, other than not being able to actually touch the bulb.
1st how are you measuring temps? And where are you measuring them?
What other lighting/heating do you have in place? UV, basking spot, etc?
If you mean that you are needing additional heat beyond the basking lamp
AND the CHE, then you can either add more lights/lamps or go to a larger wattage.
But I've rarely seen any enclosure that can't be gotten to the correct temp with a
proper sized basking lamp, a "cool side" lower wattage lamp, and a night-time CHE
(if needed).