Potterton Suprima 50 noisy

[locomtion]

My Suprima 50 is around 8 1/2 years old but has now developed kettling or banging through the pipes just as it reaches its peak heat before shutting off. I have run a descaler through it and bled everything, I also changed both the thermister and overheat stat but the problem is still there. I have tried different pump speeds and have had to turn the boiler temp right down to make the problem more bearable. I now leave the hot water/heating on constant to keep it warm, as the evening goes on the boiler cuts in and out with no drama as the temperature is constant and doesn`t need much heat top up, however have a shower and the boiler cuts in to warm the cylinder the banging is back. I`m no engineer but have done all the plumbing on this system and its been fine for around 8 years, I`m thinking maybe the heat exchanger is restricting the flow and causing the problem.
Sorry to go on, just wanted to state all the facts.

 

[gstens baxi]

The noise you describe is probably due to a build up of system debris in the heat exchanger. Try fernox system restorer or equivalent. Either that or remortgage and fork out for a system power flush.

 

[locomtion]

Thanks for that, thought it might have something to do with the exchanger

 

[Agile]

It may well be lime scale in the heat exchanger!

If you can measure the temperature accurately on the flow and the return to the boiler then you can find out if the flow rate is adequate. It should be no more than about 15*C ( target 11*C ).

If more, then blockage or pump fault or design fault.

If about 10-15*C then its lime scale and clearing it is tricky without specialised experience of using the right chemicals.

Its also possible that the gas burner pressure is too high but that really needs a CORGI engineer to check it.

Tony Glazier