Vibration when first opening hot tap after u/v cylinder heating cycle

[ShaunCorbs]

Why are you getting a second expansion vessel fitted

 

[nashant]

Why are you getting a second expansion vessel fitted

Not second, replacement

 

[ShaunCorbs]

No issue with the expansion vessel also 35l you have a 400l unvented ?

 

[nashant]

What makes you say no issue with the EV? There has to be something making that noise, and one of the theories so far has been EV diaphragm reverberation. I'm pulling my hair out and have been abandoned by the company I paid £13k for a complete repipe of heating and hot water. I'm at a point where I'm willing to spend a few hundred quid just trying stuff, it's driving me mad

 

[ShaunCorbs]

Are the pressures equal in regards to ex and cold water - .2 bar

 

[nashant]

Are the pressures equal in regards to ex and cold water - .2 bar

The main varies between 4 and 5 bar over summer, it's dropped to 3 to 4 currently. Assuming Thames Water's winter pressure level. The pressure on the combi is set to 3, this is confirmed (I think) by the pressure on the hot being 3 bar at all times apart from immediately after a heating cycle. After a heating cycle the pressure on the hot rises to 4 bar. The EV is pre-charged to 2.8.

 

[ShaunCorbs]

On a flexi ?

 

[nashant]

On a flexi ?

Nope, piped. I thought I would test the reducing valve by running the cold on a different tap that comes off the main before the combi, then opening a hot this morning. Still get the noise, didn't make a difference. So it's not the pressure on the main that's causing the problem.

 

[ShaunCorbs]

Any pictures of the unvented and pipework ?

 

[nashant]

Is it fine to have separate components instead of a combo valve? If yes, can I confirm with you the order the engineer should be installing them? I know, I shouldn't need to, I should just let them deal with it. But my experience so far has been less than stellar, so would like to be able to verify what they've done.

So should be main -> pressure reducing valve/filter -> tee off for balanced cold -> check valve -> pressure relief valve -> tee off for EV -> into cylinder. That right?

Pics attached