ok i read alot of these forums there are so many shit engineers out there its unbelivable,
1stly does the hotwater run hot then cold ? and then possibly hot, if it does its a clogged or scaled up plated heat exchanger, the boiler reaches max temp due to bad circulation through plated exchanger, shuts off!. mains water through other half of exchanger cools temp, boiler fires up again so on and so forth. in badly clogged up plated heat exchangers. boiler will lock out on over heat, and u wont be able to reset untill temp has come down. another reason may bey a weak pump not able to circulate water quick enough to exchange heat with dhw inlet through plated heat exchanger, same symptoms as previous.its obvious its not diverter. as problems due to diverters are usualy rads getting hot when you turn hot tap on,(letby) boiler not firing up on dhw demand,and in the case of lots of early turbomax boilers the rubber ball and end of rod gets stuck in opening as it swells typically as valve is in dhw mode all summer. 80% of my breakdown work is sludged up systems that knacker pumps trvs aav,s. you want to save money in long run. get a trusted gas engineer to come once a year and clean drain and add inhibitor to your system, regards GASBOILERDOCTOR
gasboilerdoctor, November 2010
