I have a myson apollo boiler it is either the 15/30b or 30/50b model.I have been having some problems with lately in january it went off altogether could not even get pilot to light,this was resolved by replacing the thermocouple. Then amonth later it went off again this was resolved by relacing the limit stat.Now aweek later it has failed again, ican get pilot to reignite burners fire up radiators and water begin to warm but after about 10 to 15 minutes it cuts out completely.The guy who installed the parts for me is out of town tillnext week i was just wondering if anyone could help with what the problem may be and what part may need replacing so i can order it.

petermac, March 2010

may be faulty pump or pump overrun thermostst. if the pump overrun stat is faulty it can stop power to the pump, and so the heat won't get out of the boiler.
i'd guess it's a slow pump however if it's running for as long as 15 minutes.
as you've already had the limit stat replaced i'd ask your engineer to replace the hi and lo stats at the same time, should only cost about an extra £10 - £15. from past experience i find it best to replace all the stats when one becomes faulty as usually the others are on the road out.

Ian, March 2010