Hammer in CH pipes

[Mike P]

I have a 120,000 BTU cast iron boiler in a bungalow. I have loud intermittent water hammer in the CH pipes. All bar one radiator have thermostatic valves. The hammer can be eliminated by opening or closing a radiator valve but usually returns. The pump is at its lowest setting and I have bled the radiators. This is an open system (i.e. with expansion tank)
Any help please? and thank you in anticipation.

 

[ch4gas]

The problem you are experiencing is likely to be caused by the thermostatic radiator valves being fitted incorrectly, with the flow through the valves causing the the valve to vibrate as the valve starts to shut down.

 

[PGatHome]

I have a very similar problem which only started after I fitted a thermostativ valve to the radiator in my down stairs bathroom. when you say the valve has been fitted incorrectly, just what could I have done wrong?
I can only guess that I may have fitted it the wrong way around or fitted it to the wrong end of the rad ( flow side/ return side). Is there any thing else I need to check for as I hate getting up at 5 am just to twiddle the valve 2 to 3 times over half an hour as the system heats up

 

[weargas]

the pump hasn't been recently fitted has it?

 

[ChrisR]

The TRV is best on the flow end, though many current makers have some which are claimed not to mind which way the water flows.

Noise can come if flow is too high (close the valve down at the other end of the rad - try just 1/3rd of a turn open) or pump pressure is too high . If the pump setting has to be high to get the flow when a lot of trv's are open, the pressure can go up a lot when only one is open. Then you need a pressure controlling valve, in the shape of an automatic bypass valve, which opens at a preset pressure.

Noise can also come from nasty cheap valves with loose bits inside!

 

[vanman]

you might find that sometimes this may also be worse when the pipes on the system have not been secured, anything over 2mtrs without a clip or support may make the prone to vibrate even more.

 

[TheIce_Man]

The problem is most trvs are mono directional i..e. they can only be fitted on the flow or the return , you can get bi directional models that make no difference which side of the rad they are fitted to,could also be the ball valve in the loft causing the water hammer i.e. the washer plate loose.