Baxi DuoTec 28HE Hot water Temperature problem

[Geordie68]

Hi Everyone,
I had the Baxi DuoTec 28HE boiler installed 8 years ago on to an existing system of 5 rads, also 2 new rads were added and the system was flushed during the installation, it has been quite reliable, but just recently I am having problems with the Hot water side. When I run the bath the hot water tap flow has to be restricted quite alot to maintain a hot flow, the boiler seems to hunt up and down just to meet the small amount of flow, the boiler temp goes up to 80-83° then the burner rolls back for a few seconds then it cycles back up to the same temp then rolls back again. I think the heat exchanger is the problem, the boiler can easily supply the heat but it is not easily being transferred to the water so is shutting down and then starting the cycle over and over. Any help would be appreciated please.

P.S. just like to add changing the temp setting on the front of the boiler makes no noticeable difference the boiler still cycles up and down constantly, no problems with the radiator side at all.

 

[gigz]

Blocked plate heat exchanger.

 

[Geordie68]

Thanks gigz, thought as much! will have contact the plumber and fit a new one, and get the system flushed again.

 

[gas112]

no need for a new one remove and clean it by filling it with brick acid for 20 minutes then flushing it out under tap

 

[Geordie68]

Excellent gas112, will do that cheers.