Noisy heating

[robatwork]

System is Vaillant system boiler feeding a Megaflo and central heating system upstairs and UFH downstairs. Controlled by 2 separate thermostats.

The upstairs rads get hot very quickly which is great, but the water passing through is very noisy. The rads all have TRVs and if they are on 2-3 then the noise dies down, but of course the rads don't get hot.

How can I get the heating to be less noisy? Bled the rads a few times - no air.

thanks!

 

[MeldrewsMate]

You could try closing the lockshield (manual) valve at the opposite end of the radiator. You will notice the change in noise immediately. Start with the lockshield open only half a turn from off, then leave it for several minutes. There should be a discernable temperature difference between the hot end and the very hot end (TRV end). If not close the valve a quarter turn at a time until there is, if there is then open it a quarter turn at a time, leaving 10 mins between each adjustment. You are aiming for about 13C temperature differential between flow (in) and return (out).
The final adjustment will be specific to YOUR system and YOUR radiator (bigger rads open more than smaller ones, towel warmers generally only 1/4 to 1/2 a turn from closed.

Once that has been done reassess the noises. If still not acceptable you may have to install an automatic bypass valve (ABV), though if you can adjust the pump speed (on some system boilers it's a parameter that can be changed to do this) to a lower setting this may also alleviate the problem. Be careful though, as you may need a higher pump speed in the depths of winter. An ABV is generally a good idea in any case.