Hi
Great forum btw!
I have a Vaillant EcoTech 418, S-Plan system, 2 zones (HW unvented cylinder + CH), installed 1 year ago. Standard 3 speed Grundfos pump.
The system seems to work, but boiler periodically (say once a month) cuts out with error F72... "Flow and/or return NTC fault".
I've now...