What is the pressure in your loop?
Based on what you have posted, I would suspect either the DXM2 control board is not outputing the proper signal to the variable speed pump, or the pump isn't responding appropriately to the control signal.
Watch the following video on Waterside Analysis Procedures on vFlow Units and follow the procedure shown to see if the pump is responding appropriately to manual demand control signals.
https://www.youtube.com/watch?v=OfjHznrx0T0 The following troubleshooting guide is also useful:
http://www.climatemaster.com/geothe...-pumps.pdf Climatemaster literature for the TZ 22 series heat pumps including the troubleshooting guide can also be found here:
http://www.climatemaster.com/geothe...rature/tz/