Poor man's variable speed pump

How do the Grundfos change speed? Are they PSC motors with additional windings? I never took one apart.

They appear to be just as you say - PSC with multiple windings. Interesting that this thread resurfaced one year later to the day from its last posting. The circulator has been working fine since I started this thread.

I'm now playing with a commercial variable speed controller that looks like a very cost effective way to provide a high degree of control for PSC circulators as well as most fans. Reports to follow at some point in a new thread.

I assume the point of this is to have automation control? I mean computer controlled via digital or analogue interfaces? For a manual speed control I just use the quadrac off a cheap dimmer and add a 40W resistor and a triac and I'm off and running. Depends on the draw of the device as to what components you use. I even made a remote control for the old man using this method . In our case it controls the big blower motor that vents the compressors outside. It responds to the same remote control we use for the gas pumps. It literally interfaces by changing the position of a cog up or down to change the output to the blower. He can't handle a computer worth beans but a two button remote is right up his alley (up, down). I could use the same method to control it from anything with a hard wire interface. I know the approach depends entirely on motor type and tolerances.

After doing more research. A common way of controlling a PSC motor for multiple speeds is using different tap locations on the capacitor winding. Makes sense.

Another way to control it is voltage. PSC can go down to 50-60% in voltage and still run well. I wonder, multiple speed settings combined with variable voltage at each setting - sounds like a controller to me. I think the EKO fans do something similar.