I believe that does not hold true for ECM motors. even if it doesn't, the ECM pump's maximum draw is typically significantly less (like half) that of a PSC pump of equivalent power.

I have to admit I'm not using ecm pumps yet and have no argument with them or the energy savings and ease of incorporating them into the design. I have installed a lot of centrifugals with vfds and understand how they work as I went thru Toshiba's vfd school years ago. Anymore I am slow to adapt to new products as I have experienced a few such as Glowcore, Pulse, Complete heat, Voyager, and at the beginning of my career the first generation of condensing furnaces and later the fist variable speed fans. I guess I'm getting old and don't like service headaches. I'm not calling ecm pumps a service headache and we will use them and have when speced on commercial projects

Multiple pumps, old style expansion tanks...why not a coal stoker? It is easy to tell the armchair and learn-by-google from the real-world innovators. I saw GlowCore as a stepping stone to a better view.

We have been using the TACO Variable speed delta T pumps on a lot of projects lately, big and small.
Very reliable, I can increase pump size for a wide range of applications and they will ramp down to almost nothing. So a lot of ground can be covered with one pump and a hand full of zone valves.
Dan
PS happy post T day all, still on left overs here..