I have that exact same panel - and you should be able to feel the warm water coming in the return when the sun it out. The panel itself should be cool when pumping water through it. If it is hot it means the valve is closed or defective. The valve itself is kind of a PITA - mine is on the ground and it gets bumped of moves on its own. I'm in northern Ohio. My pool water got up to 92 this week. (18 x4 ).