Boiler starts up, runs for 10 seconds then stops. Actions taken, check and cleaned pump head. ( does run and no debris in inpeller) isolated all but two rads which are i know are clean and tried running and have sentinel x800 the system, when it initially happened i did give the pump a little clout and it worked for a day, then it now never runs for more than 10 seconds and then does the F22 or ocxasionally f24 error coded. I think that leaves debris in PHE or faulty pump, NTCs, PCB or powerflush needed. Any ideas guys, have i missed anything, Next step is engineer but just posting this first for any reaction. Many thanks, HNY!!!