If they are supplying the Buderus with the built in reset controls you wonÂt have to change or replace anything other than adding a spring loaded differential bypass valve. The reset control will activate the circulator on drop of outdoor temperature and adjust the water temperature up or down to match the load so that the control valves stay open (which is what control valves are supposed to do) and in the event of overheating (solar gain, kids come home with the soccer team, cooking in the kitchen) then the thermostatic valves you have will modulate closed, the resulting rising head pressure on the circulator gets applied to the bypass valve and it opens and bypasses flow back to the boiler - voila  constant flow variable temperature systemÂ.it doesnÂt get any simpler. If you want some fine tuning  order the boiler control with a single RTU for control feedback  locate it in a representative area  kitchen/nook is generally a good place. A few more details to consider beyond this discussion but a competent manufacturers rep or contractor can handle it. Benchmark for bypass valve: Danfoss, Braukmann or Oventrop.

Well I've done some more research on this and other forums and educated myself some. Apparently a 2-speed pump still works for solar by priming the panels w/ the high speed and then switching to the slow speed for circulation. Currently I'm leaning towards and intelliflow 4x160 pump with the EasyTouch controls. I've read the online manual for the easytouch and it seems like it handles the solar aspect well. I'm going with the 4x160 pump because I like the adjustibility and want to ensure I have correct flow through the floor cleaning as well as adjustibility on the spa jets. Sounds like it'll be a hell of a system. Now I just hope the PB doesn't try to rape me on the price.

A 2 HP pump does push too much water for a 1.5" line. I don't like to see more than a 1.5 HP when the water path has a 1.5" line feed. If there is no spa or water feature, a 1 HP will be ample on most pools. If there is a large distance between the filter and pool, a 1.5 HP may be needed. Replacing the back half of the pump can be done fairly easily. For most Haywards, split the pump halves. Replace the impeller, diffuser(with gasket), seal set, seal plate housing gasket, and motor to the most approriate size. No plumbing changes needed. Scott

Thanks for the reply. I actually just made another post (http://ths.gardenweb.com/forums/load/pools/msg0722274229075.html) probably while you posted this. I would like to run solar most of the time. In South Fla I pretty much leave it up to the current control (Aqua Solar) when to run, which is pretty much any time the roof temp is 20 degrees higher than ambient temp. Many times that is full 8 hour day. My latest concern is if I do just use a single speed like Whisperflo, I am concerned at some of the pros here warning against AO Smith motors which apparently are now used on Whisperflo. This is a real head scratcher and I don't want to rush into a $500-$1000 mistake. In other posts and forums I do see some people using VS/4x160 on lower/medium speeds successfully with solar. Mine is only a 1 story and short piping. As far as automation, I prefer to do it on my own if the Intelliflo protocol is open, rather than spending alot extra on redundant control systems.