1. The problem statement, all variables and given/known data Calculate surface temp of heat exchanger when it's heating the room with the known power of P. Room temperature T is also known, as is the heater surface area A. ε ≈ 1. 2. Relevant equations P = εσAT^4 is what I've been trying to use. 3. The attempt at a solution I've been trying to solve this with T = (P/σA)^0.25, but that's giving me negative surface temps which clearly can't be correct. I'm guessing the reported heating power P can't be the actual total heating power of the radiator, but I haven't been able to figure out how to go at it.