Worcester 30si pressure rise

[kozak1968]

Hi, I have an occasional problem with a 6 year old si30. When the hot water is turned on the pressure goes up to 2.5 bar. The tap runs cold then when the tap is turned off there is a banging noise as if something is trying to move then the pressure drops back to 1 bar. Any ideas ?

 

[Mike Jackson]

could be faulty pump or expansion vessel.


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[danny@phase]

Same answer as mike, pump or expansion vessel.....

 

[kozak1968]

Thanks will give it a go

 

[Millsy 82]

Also check Plate heat ex and diverter valve for blockages/sticking. Wouldnt have thought it would be expansion vessell unless it only does it when htg is up to temp.

 

[gasmarc]

well it could be a variety of things , I had an expansion vessel last week that i pumped up to over 3 bar in no time then the pressure just dropped to zero in one go,

 

[dancinplumba]

Also check Plate heat ex and diverter valve for blockages/sticking. Wouldnt have thought it would be expansion vessell unless it only does it when htg is up to temp.

it will still do it with dhw and even quicker

 

[Millsy 82]

The only times I have seen it happen on dhw it was a blockage somewhere usually in the plate or bypass pipe as ch circuit would also take up some of the expansion unless it was a very small system.

Thats the reason I would personally check the plate for blockages before I would check the expansion

 

[dancinplumba]

divertor closed to ch circuit, boiler goes to full flame, heats up boiler rapidly, water in boiler expands quickly, due to pump or blockage in dhex or main hex

 

[Millsy 82]

The diverter valve is closed but its on the return by the pump which means the flow to ch still open so unless the ch is piping hot it will allow for some expansion.

 

[dancinplumba]

carnt expand up return, path is closed as divertor closed you carnt compress water

 

[Millsy 82]

Its the flow thats constantly open not the return the return has the diverter valve in it.

If the heating circuit is at 1 bar it will not stay at 1 bar when the boiler is at 2.5 bar even with the diverter shut

 

[dancinplumba]

no it wont, but it will get there faster on dhw

 

[glenno1]

when you run hot water is there any temp rise in flow and return pipe