Grindng noise from central heating

[DaveDiyNot]

Earlier today my central heating pipework start to emit a loud grinding noise. I traced it to the radiator in the entry area, which I only turn on when it is really cold.

The thermostatic valve was shut and the noise disappeared as soon as I opened it a tiny bit.

I would really appreciate any ideas.

Thanks

Dave

 

[MeldrewsMate]

To confirm my impression of your complaint; the radiator is normally shut off, and it was shut off at the time that the noise started (ie the state it had been in throughout the milder weather. You had done nothing to change its state BEFORE this noise started.

In response to the noise you opened the radiator valve slightly (the first time you had touched it for several days/weeks/months), and the noise stopped immediately.

If that is correct?
When turned on, which end of the rad gets hot first? The TRV end, or the non-TRV end?
It may be that the TRV has reverse flow and, as it gets near to it's set temperature, the venturi affect (more correctly the Bernouilli effect) causes the TRV plug to vibrate above its seat. Test for this by opening the valve just enough to stop the noise; as the room temperature increases the noise will recur, and altering the setting again (up or down) will silence it.
The solution is to fit the TRV to the other end of the rad, or change it for one that allows bi-directional flow.

 

[DaveDiyNot]

Sorry. My brevity was misleading.
I had turned that radiator on for several cold days before today but today I started up the boiler with it turned off and it had been running for quite a while before the noise started. I’ll try your suggested test tomorrow morning.

 

[DaveDiyNot]

The TRV end gets hot first

 

[DaveDiyNot]

And when I shut the TRV off no noise!!!
That is an overnight change.