I see your a bit of an experrt on the later duo tec, i am an engineer but this is the first duo-tec GA i have come accross with a hot water fault. I would very much appreciate a little insight from yourself. I have cleaned the inlet filter and inspected the flow turbine which appears to revolve freely. the inlet connection has a blue flow restrictor in it ,however her is the fault . When the mains supply is on full i get around 18lpm at the tap but the boiler wont fire and no red indicator on the Hes but If i reduce the flow rate down to 9 lpm the appliance fires up fine with a constant red led on the top of the hes. have you come accross anything similar.?