Worcester 30si hot water fault.

[billski]

Worcester 30si combi boiler, hot water doesn't stay hot. Boiler stays lit & seems to be happy, diverter valve working as it should, central heating works fine. Flow rate at the tap is above what it should be, but it has worked fine for 9 years. Replaced tem sensor, even though it tested out okay on my meter, no change. Next I'm thinking plate to plate heat exchanger, but the flow rate doesn't seem restricted and it's not cutting out. Could the flow turbine be faulty? If so can I test in?
Appreciate your thoughts.

 

[ShaunCorbs]

Plate

Test the temp drop across the plate both end eg both heating and hot water sides of the plate

 

[billski]

Should the temp drop be minimal?
And could it still be the flow turbine?

 

[ShaunCorbs]

Should the temp drop be minimal?
And could it still be the flow turbine?

Should be decent eg flow 70 return around 20 is depending on hot water eg 50dc

No as it's staying fired

 

[billski]

Cheers I'll check. Are you thinking the plate could be blocked in the heating part then and not the dhw side of it?

 

[ShaunCorbs]

Yes with the flow rate being good hot water side so not block with lime scale etc

 

[shaky]

Flow restrictors can fail on theses letting the flow of water go above what the boiler can handle.