Ariston Microgenus 27 MFFI - Overheating boiler please help!

I've been looking everywhere for a user manual for this boiler online but it's impossible. Bought 4 year old house, my system was totally drained so refilled, bled radiators etc. everything was ok initially & heating worked for few days.

Now however when turning heating on the boiler fires up but the temp continues to rise until it shuts off after 30-60 seconds! It's as though water's not being pumped around the system or something. Rads stay cold and I need to run hot water tap to reduce temp in boiler (water is super hot!)

Can anyone help me with this? I can't take another week of wearing my coat and scarf in the house!

Thank you

does the flow pipe to the rads get hot? could be a seized or choked pump if it was left dormant for a while.

Thanks for your swift reply.

Do you mean the pipe just underneath the boiler? If so then yes it does get hot. It sounds like the pump is running even after the flame is shut off.

Niall