Boiler knocking

[oldskoo1]

Hello

I'm looking for some advice on a knocking boiler. The boiler is most likely kettling I think.

Within a couple of mins the ideal classic ff380 begins kettling. The system was drained last year and the system water was clear. I've drained a bit off and still clear.

I still hear the kettling when the hot water comes on. Pump makes no difference but has to be on speed 3 as it is a 3 storey.

I'm thinking the heat exchanger is dirty and air bubbles possible the issue. Or maybe pump cavitation?

Is fernox the solution here? I assume the rads are the only easy way in so might wait until the autumn. The kettling should be ok until then?

Thanks

 

[45yearsagasman]

If your system water is ok and you have ensured pump is ok, then introduce some "system silencer". Fernox or Sentinel produce it and is easily added direct to a rad and circulated to the boiler. I've used it many times with success.