heating water hammer at boiler

[alancoulson1]

wall mounted in garage gas boiler has started to suffer from bad water hammer on heat up really bad water surging can be detected in the flow line.
anyone any ideas, have checked and there doesn't appear to be any air in the system, pump is on the flow to a 3 port zone valve, has an auto system bypass valve fitted close to the pump. Flow to the cylinder is 15mm, heating circuit 22mm.

 

[Dan Robinson]

Can't beat a bit please and thank you.

 

[45yearsagasman]

pump workin?

 

[alancoulson1]

yes pump is set on speed 3, it was replaced in March this year

 

[Charnwood]

wall mounted in garage gas boiler has started to suffer from bad water hammer on heat up

That sounds more like kettling.

"really bad water surging can be detected in the flow line." Detected how?

 

[gas112]

What boiler ? could be boiler stat has gone and water is getting too hot and banging through the pipes

 

[alancoulson1]

OK well the boiler stat works fine, it is possible to feel the surging in the flow pipe near the boiler.
I think that you are correct its more likely to be kettling, is this caused by scale build up in the heat exchanger ??
the boiler is a Halstead 18KW

 

[Charnwood]

I think that you are correct its more likely to be kettling, is this caused by scale build up in the heat exchanger ??

Yup.

In hard water areas, lime scale deposits build up on the heat exchanger and restrict the flow of water.

When the flow of water is restricted (trapped in the heat exchanger) it becomes too hot and starts to steam, boil and therefore expand. This is what causes the noise and sounds like a kettle boiling, hence the name.

Other debris from the system (sludge) can also collect on and around the heat exchanger causing the same problem.

Kettling reduces efficiency and boiler life hence rectifying the situation is actually cost effective as opposed to a wasted outlay of funds.

It is vital to remember that only a Gas Safe registered Heating Engineer \ Plumber can work on your Gas Boiler.

 

[alancoulson1]

OK thanks Charnwood. I will have the system chemically cleaned as soon as I can have the heating on, I think for now I will switch the boiler off and use the immersion for hot water.
Does the company I use have to be 'gas safe' even though they wont be working on the gas side of the boiler, can I use a plumber to do the descale.