Ideal Class FF240 - Kettling?

24 Sep 2008
Reaction score
United Kingdom
Hope someone can help me with this little problem. I have an Ideal Classic FF240 gas boiler, which feeds central heating and hot water.

There is a cold feed in the loft and a hot water tank. It has a Honeywell v4073A valve and Grundfos 15/50 Selectric 130 pump.

The whole system is about 8 years old from when the house was built.

Recently, I have started to get a banging noise from the boiler when it has been running for about 20 mins from cold.

It isn't really loud but is noticeable and something doesn't seem quite right. I think the term is kettling? Nothing has been changed or added to the system recently so not sure why it has suddenly started. It is not a constant bang, it does it every 20-30 seconds or so. Sometimes you hear running water through the feed pipes too.

The rads are fine - warm up nicely, and hot water is fine too. I have tried bleeding the rads but no trapped air.

I have tried turning down the thermostat on the boiler (currently at 4) and when I do the banging is certainly reduced but still there.

Finally, the pump is on setting "2". If I increase to "3" the banging does reduce and is quiter/less often.

Any ideas before I call a plumber in to take a look?
Sponsored Links
Could be air accumulating - see if there's a vent point by the cylinder.
Could also be the boiler thermostat failing, a slow pump, or sludge building up n the system. A surface temperature thermometer is about the only way you can be sure.
take the head off the pump. i bet you will find debris in the pump impeller.

If this is the case then replace the pump. You could clean it and would work for a while but they usually give up a few months later.

Open vented systems which have not had new inhibitor added every couple of years are common to corrosion.
Open vented systems which have not had new inhibitor added every couple of years are common to corrosion.

i wonder why it is that inhibitor requires replacing at such regular intervals.

i seem to recall the old mb1 i used to use in the 80s had a life of perhaps 20 years if never drained.

the march of progress eh, a wonderful thing to behold. :eek: :confused: :) :D :LOL:
Sponsored Links
Thanks for the advice. There is a vent point by the cylinder and when I opened this gradually a fair bit of air came out....

I will take the head off the pump too and have a look. I added inhibitor when I moved in about 8 months ago but doubt the previous owners did at all!

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local