Pan pipes type noise from radiators, what could be the cause?

[krav]

A friend of mine asked me to investigate what might be the cause of this rather musical radiator sound:

He told me that a plumber already bled the air from the system, so I am looking for any ideas that you guys might have.

Thanks for any help!

 

[muggles]

Is it definitely coming from the radiators? Sounds more like a ball valve to me. If it is definitely radiator noise, is it just one, a few, or all of them? What system type is it? Combi? Heat only? Sealed? Open vent? Is it a continuous noise or does it come and go? Can it easily be replicated, and if so under what conditions?

 

[krav]

The system is a closed one. With a regular Bulex gas boiler (i.e. not condensing and not combi).
Not all of the system makes the noise, nor does the noise happen all the time. It apparently happens at random, as I do not live at the property, I have not yet been able to make an accurate assessment of what the conditions are when the noise occurs i.e. recreate it.
It seems that only two of the radiators in the system make the noise and they are located on separate floors but directly above/below each other on the same side of the house.

 

[ianmcd]

do they have TRVs fitted ?

 

[krav]

Yes, there are thermostatic Radiator Valves fitted

 

[polesapart]

does the noise stop if the TRV setting is altered?

 

[Dangee]

Peruvian's, that's who I blame!

 

[ianmcd]

when the noise is present close the TRV and if the noise stops that is the culprit

 

[krav]

The tenants of the house seem to think that closing some valves sometimes makes the sound stop although which valve stops the noise apparently changes.
As there are only four rads that make the noise, i will replace the trv's on those ones and see if that makes it disappear
Thanks for the suggestions, I'll let you know what happens.
David

 

[ianmcd]

The tenants of the house seem to think that closing some valves sometimes makes the sound stop although which valve stops the noise apparently changes.
As there are only four rads that make the noise, i will replace the trv's on those ones and see if that makes it disappear
Thanks for the suggestions, I'll let you know what happens.
David

Modern TRVs are bi directional,
but older ones arent and if they are fitted at the wrong end then that noise will happen