Combi Boiler NEw problem - blockage?

[John Stanwell]

Boiler comes on and after a minute or so goes out. On both heating and hot water. Sometimes the overheat needs resetting, sometimes not and the pump runs and the cycle repeats.

I think there's a circulation problem, but not sure what else to try. I've bled all radiators, magnaclean and pump, the pressure is 1.5 bar. Anything else I can try / do? Thanks for your help.

 

[ianmcd]

Make and model of your boiler might give us a head start

 

[John Stanwell]

Combi boiler. Baxi 80. Not condensing.

 

[John Stanwell]

More info: some of the rads heat up - some hotter than others, some have always taken longer, and boiler is now cycling, coming on for a minute or two and going off, always had trouble with 2 rads in back bedrooms, think it is balancing issue but we have lots of 15mm drops. Overheat doesn't seem to trip now.

 

[ianmcd]

Diverter valves on these can be problematic, run a hot tap with the heating switched off and see if the heating flow gets hot if it does the Diverter valve needs servicing

 

[John Stanwell]

Thanks for replying. Some of rads have cold spots and have for a while, but getting hot now, just a little slower than before. Might get a cleaner and put into system, X400 or something like that

 

[CWHEATING]

Sounds like the pump to me.

 

[John Stanwell]

Pump's only been in 4 months, is a Grundfos on speed #3 setting!