I have one automation controller, a Pentair EasyTouch, that controls everything, including solar. It pairs with my Pentair 3HP IntelliFlo pump, SWG and all the valve actuators (also Pentair) and temperature sensors than are required to heat, sanitize and clean my pool. I can control everything at the pad, from inside my home on a wall mounted controller and on any of my computers and mobile devices, including from anywhere in the world. Pentair also makes a newer version controller, the IntelliCenter, that does all that, too.
If it's in the budget, that's what I would recommend.
You can certainly run a pool manually, even solar, and with a smaller, less expensive pump. But you'll be running to the pad several times a day to do so. Or you could go with Pentair's SolarTouch, for control of the solar heating system only. I don't have any experience with that unit, but I've heard it is difficult to program. Pentair also has something called SunTouch, which I just today discovered. Perhaps that is an improved version of the SolarTouch. Sorry, I don't know anything about that one, either. It looks like it can do solar, pump and SWG. I would recommend you download the available owner manuals on IntelliCenter, EasyTouch, SunTouch and SolarTouch. Read 'em, and gain a full understanding or what they each can do (any can't do). I wish I had gotten that advice before I purchased my EasyTouch PSL4. I didn't know at the time what that could do, or what I would later want it to be able to do. It turned out to be the wrong unit for me (I've since upgraded). Pool automation is like buying a computer: you first figure out what current technology allows (in terms of what functionality is possible), then you decide what of all those capabilities you want for yourself, then you figure out what controller can do all those things at a price you can afford.
@mas985 can help with the mechanics, but I expect 2" PVC will be fine. I avoided all calculations by installing a FlowVis flow meter. With my solar panel manufacturer's spec for optimum flow rate, a variable speed pump and the flow meter, it was a very simple matter to adjust the pump's RPM to achieve a flow rate that assures me of the most cost effective heating possible. I also used the manufacturer's specs to determine how many panels I needed for my size pool. I didn't delve into things like heat loss or pump head. I use 8 panels for a 12K gallon pool and get a 5-10° bump on most "swim season" days. I don't heat my pool year-round. 3HP could probably serve my panels if they were across town! OK, that's a slight exaggeration, but with a 3HP variable-speed pump, you'll pretty much be covered.
That's pretty much what I know about the subject! That, and what I learned about plumbing solar heating systems from the following website (along with some other internet research). I installed my system myself, using the very highly-regarded Heliocol brand of panels, and saved myself about $7K. Heliocol has an excellent system of connecting and mounting panels, which has so far proven maintenance free. If you poke around on h2otsun, you'll find some excellent diagrams that explain how solar works, and how best to install the panels and plumbing.
The state of the art in the adaptation of solar pool heating to various roof types and pool mechanical systems.
www.h2otsun.com
That all said, I used all premium products. My Pentair gear and the Heliocol panels and even the black UV PVC I used on the roof come with a permium price to match their quality...
