baxi combi instant 105e - noise problem

[dreamcatcher]

After the hot water tap is turned off there is a noise from the boiler that lasts anything from a few seconds to several minutes. This only happens when the CH is also on. The noise sounds like it is a valve trying to open/close. The DHW and CH pressure differential valve diaphragms have both been checked and they are fine. Everything works as it should except this noise.

 

[Baxmax]

High pitched whistle/screach Divertor valve

 

[dreamcatcher]

it's more like a clanging/clunking/rattling sound.

 

[elexgas007]

can you check the expantion vessel ,it sound like it's full of wather rather than air--does the presure guedge move up as the boiler starts up?

 

[dreamcatcher]

it was the expansion vessel and we had it fixed a few months ago