Ideal Class FF240 - Kettling?

[sjmorgan]

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?

 

[ChrisR]

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.

 

[snb]

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.

 

[spacethegas]

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.

 

[sjmorgan]

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!

 

[cypher007]

did you solve the problem?

whoops just seen how old this thread is.