Searcher is right in that the pump is oversized IF you direct all the flow through the panels either way they're hooked up, series or parallel. As we said, the trick is to flow enough water through the panels to do the job but no more.

This statement "To look at it another way, if you would put a 2 HP motor in place of the 1.5, you would not move any more water but you would raise the pressure considerably more." is not totally true. At higher pressure you would move more water but in your situation you don't need to do this. Through any pipe or restriction, higher pressure = higher flow.

Does operating at a higher pressure hurt the pump? I'm not really sure but I tend to say slightly. I think the shaft seal is in a high pressure area and if that is the case then running at higher pressures would increase wear and decrease seal life. Motor bearings aren't affected. Running at higher pressure is a waste of electricity however.

I stand by my statement that either a series or parallel hookup will work but parallel is preferred. There is a slight thermodynamic advantage of parallel over series. A simple way to look at it is in series the first panel is preheating the water for the second panel. You get maximum heat transfer (or absorbtion) when you have the largest temperature differential which means you want the coldest water through both panels. Thus parallel wins. In a practical sense, hook them up whichever way is easier and cosmetically better.

Al