Unvented Cylinder Noise

[adorableade]

I have a new unvented system installed a few months ago. It has started to sometimes make a loud vibrating sound when a hot water tap is first turned on. The noise only lasts for a few seconds.

The installer has been out a couple of times and solved the problem for a bit but it keeps coming back. I think he was altering the pressure in the expansion vessel.

I have (on his advice) been recording the mains and EV pressure to see if there was a pattern. Last time the mains was at 2.8 bar and the EV at 3 bar. After running the tap and having the noise the mains dropped to just over 2 bar and the EV to 2.6 bar. Sometimes I have had similar readings but no noise!

Any ideas for me to suggest to the installer to cure this? He seems to be at a loss now and not keen to keep coming back. Should there be such a fluctuation in the 2 pressure readings? Should the EV pressure be lower to match the mains?

Any advice that I pass on would be appreciated. The cylinder is a stelfow 210 run off a Worcester Bosch Greenstar 30. The installer is G3 qualified.

Cheers

 

[mickyg]

match the EV pressure to the working pressure of the system.

 

[adorableade]

Cheers for the super fast reply micky. I guess he set it to 3 a that is what the manual says. The mains seems to fluctuate between 2 and 2.8 bar. What should the EV be set at to cope with that?

 

[dcawkwell]

Drop the expansion vessel pressure it is only a tyre valve at the top

of the expansion vessel. Let a few lbs out should sort it out.