Hi Peter - I have the same setup, and get an itermittent "En" - Yes - not E1 or E2, but En (E with a little n) error on the Atlas display. Any ideas ?
I have a Geyserwise to circulate the water between geyser and roof-top tubes, but find it is actually quite noisy - It's in the roof above my bedroom - I don't normally hear it unless I'm having a Sunday nap 🙂