Worcester CDi showing incorrect pressure?


5 Aug 2008
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United Kingdom

I have a Worcester CDi configured as a system boiler into an S plan system. Only the heat flow and return are connected on the boiler, not the DHW.

Above my OSO tank I have a filling loop and pressure gauge. This pressure goes up when I open the fill loop and went to 0 when I drained the system.

So far so simple. However the boiler pressure gauge shows 1.5 bar regardless of the system pressure. I can't find a second fill loop anywhere. Any ideas what pressure this is showing and does it need any mantainance?

I can't see an external expansion vessel anywhere so I presume the boiler one is used.

Also, any idea why you might fit a combi instead of a system boiler? The tank is older than the boiler so it was never used as a combi.


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The boiler pressure guage has a very small diameter capillary tube and it is common for this to be blocked where it connects to the hydro block hense the pressure guage reads constant

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