On 16/03/2013 11:53, Andrew Mawson wrote:
We've recently had a 'Continental' brand under floor heating system
installed which works very well indeed, however at times it whistles!

The noise emanates from the mixing / temperature setting valve on the
manifold and is at a very high pitch (top of the audio spectrum). If I
slightly adjust the setting, the noise stops, until (presumably) it
comes back to the new set point, when the noise starts up again. Has
anyone else experienced this with their system? I am about to contact
the manufacturers, but would like to be armed with more information if
it is available.

My own self installed 4 zone system used to be a bit on the noisy side.
The manufacturer said the circulating pump should always be set to speed
3 (fastest) but once 2 zones have shut down the remaining zones/circuits
are too restrictive for full power and can make a little noise.

I dropped it down to the middle speed setting on the pump a few years
ago and it's fine. Still managed to get recommended flow rates on each
circuit when all were calling for heat and it cured the noise completely.

I don't know whether the (my) mixing/blending t/stat would whistle as
the supplied temperature is and always has been set lower then the
manifold 'stat.

You could try dropping the boiler temp down to 60 degrees (or less) and
set the manifold 'stat a few degrees higher just in case and see if it
provides enough output from the radiators (I presume you have a mix of
radiators and UFH)

My own radiators give more than enough heat at UFH temp 55 deg. and
they're not particularly over sized.

Cheers
Pete@

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