Expansion vessel performance

[RK_London]

Hi...I need some help understanding an issue with my expansion vessel connected to my unvented cylinder. My understanding is the expansion vessel helps regulate the pressure in my unvented hot water system. Does the expansion vessel performance affect the central heating system?

Reason I ask is my installer is suggesting fixing a known fault with the expansion vessel as a way of solving my problem of banging central heating pipes. Just don't know enough to understand. Would appreciate if someone can help me out with an explanation

 

[cross thread]

On a unvented cylinder it may have its own ex vessel that is just for hot water expansion only

 

[RK_London]

That was my understanding - so there is no connection between expansion vessel and central heating system?

 

[cross thread]

Central heating may have its own ex vessel, heating ones are normally red ,and water white but not always

 

[RK_London]

Just have a white one - central heating has vaillant boiler - no vessel

 

[kidgreen61]

Your boiler may be a system boiler which contains its own exp vessel, the two are in no way connected.
The expv on your unvented cylinder is there to accommodate the expansion of the water in the cylinder as the water is heated, it should have no bearing on on HW performance.
Other controls on the cylinder however may affect preformance.