Pump Sizing Question

[mas985]

I think most controllers that control solar will switch to high speed by default. I know for sure that mine, AquaLogic, will definitely do that.

As for head curves, is the pump you are considering on this page?

The single speed and two speed versions will have the same head curve on high speed. Low speed is simply a scaled version. But looking at these pumps, I would like to see a little more flow rate at 50' of head. But you might ask the forum if anyone is using one of these pumps for a two story solar install. But if you want to be safe, I would go with an IG pump. Something like a 1 HP SuperPump, I know would work.