I have a 6 year old Nordic ground source heat pump. Has been working well. Over past 2 weeks I have heard some screeching noise and now banging noise coming from the desup system. I have it looped through a separate buffer tank before the pre-heated hot water goes into my powered tank. The noise goes away when I turn off the desup pump. If I wait it starts up and there is no more noise. I have audio file with the recorded sound. It is attached to this thread. This is the latest- It has been cold and the system has been running a lot. We have not used much HW in the house over the past 2 days. and now the desup system is having a pulsing banging noise every 2 seconds. The water in the buffer tank is 140F. SO this is what I did. I used about 5 gallons of hotwater and the cold well water went into the buffer tank and the noise went away. Now the system has been running for 90 min and still no more noise. Hmmmmmmm Thoughts?