"Graham." wrote in message
...

On Sat, 16 Mar 2013 16:10:35 -0000, "Andrew Mawson"
wrote:

"Brian Gaff" wrote in message ...

Some ordinary valves do this, its a kind of hiss with an hf whistle. I
always put it down to the restriction at the valve as its altered
causing
turbulance in the water.
Brian


Oh yes I'm sure that you are right - it's classic feedback oscillation.
And
I'm equally sure the solution is to increase the damping on the valve, the
problem is how, as it's a sealed module as far as I can tell.

AWEM

Is it possible the valve has been installed incorrectly, with the
water flow reversed?

I understand that some TRVs whistle if fitted to the return side of a
radiator.



No the plumber checked that today

AWEM