My hot water recirculator has stopped working. The Grundfoss pump is still pumping however there is no circulation?
How do you know pump is pumping?
I have a rotation tester that I got from The Grundfoss distributor. You hold it up to the end of the motor and it shows you which way the pump is turning and how fast.
If you know pump is working than I would suspect recirc line should be purged. suspect air pocket, this would stop circulation totally. Or impella problem.
Wallynut said exactly what I was thinking. There's probably an air pocket in the line.
What about the check valve?