For what its worth I had a 4x2x2 enclosed system within about 18 inches of an old fashioned Parkray ,which of course was only lit in winter same as a radiator . I had no issues that I can remember with heat. I also had a bigger tank in a SW facing conservatory which often got very hot , no probs there either. But obviously no direct sunlight on it . My conservatory is like a jungle room ,so its shaded but hot.