Central Heating Problems - Over temperature, knocking pipes

[Rich147]

Hi

Please excuse my ignorance.
I have a problem with my conventional central heating system.
The boiler (Ideal classic FF280) occasionally (every couple of days) trips on over temperature. Prior to tripping the central heating pipes make very loud banging and knocking sounds for a few minutes. Once the boiler has tripped I can reset it by depressing a small black button the side of the boiler but the boiler will not re-start until it has cooled down (usually the following day). Once reset the cycle is repeated with the boiler tripping again within a couple of days. Several parts (temperature switch, gas valve, fan) within the boiler have been replaced along with the central heating pump and 3 way valve.
I'm considering replacing the boiler but not sure if this will resolve the issue.
Note, when the boiler is running all the radiators get to a good hot temperature.
I would very much appreciate any suggestions as to what is causing the problem and best solution.
Also if I do replace the boiler would you recommend a conventional or system type?
Thanks, Rich.

 

[Riley]

Who replaced the bits I would be tempted to get the engineer back as he clearly hasn't fixed the issue

 

[Riley]

Oh and welcome to the forum :smile:

 

[gassafe]

Flush the system with cleanser

 

[Sparkgap]

Check pump speed? Sounds like not enough flow and getting localised boiling.