Many thanks for the replies, will post wiring pics in the morning. Have held the set and ch buttons for ages, repeatedly, and I get nowhere. Old unit was 8 pin backplate with links and new one is six terminal that says it doesn't need links as they're internal.
Hi,
Problem: Original controller (Horstmann H527) was no longer controlling either the heating or hot water. It was powered up, lights were on but when it was supposed to be running either function there was just a low, electronic, hum coming from the unit and the boiler wasn't firing up.
I...