Central heating shock arrestor?

[Mister Banks]

For quite a while now I have had issues with water hammer when the central heating pump turns off. This is on a pressurised system with a Worcester Bosch Greenstar 24i boiler. I have seen that you can buy shock arrestors for water hammer but they all look to be for cold water supply and not central heating. My boiler has an expansion tank so should this provide the same function as a shock arrestor?

 

[Mottie]

For quite a while now I have had issues with water hammer when the central heating pump turns off.

I don't know what setup your system is but with or S plan system we always used to get a loud bang when ever the water or heating shut off. I eventually traced it to the automatic bypass valve - must have been sticking slightly. I wasn’t too concerned but after some work on the system I refilled it with fresh inhibitor and it stopped! I can only assume the inhibitor had some kind of lubricating property.

 

[ianmcd]

Check any zone valves you have are installed in the correct direction, if wrong way round they will still work but some clunk when closing

 

[Mister Banks]

I don't know what setup your system is but with or S plan system we always used to get a loud bang when ever the water or heating shut off. I eventually traced it to the automatic bypass valve - must have been sticking slightly. I wasn’t too concerned but after some work on the system I refilled it with fresh inhibitor and it stopped! I can only assume the inhibitor had some kind of lubricating property.

It is an S plan system with an ABV. I wonder if the ABV needs adjusting, when the ABV activates the boiler rattles!

 

[Mister Banks]

Check any zone valves you have are installed in the correct direction, if wrong way round they will still work but some clunk when closing

The valves are installed the correct way.

 

[Mister Banks]

Just checked the setting on the ABV, it’s set to 2.75. I have tried to check if this is the correct setting but I don’t know the speed setting for the boiler pump or what the boilers minimum flow rate is.