Worcester Greenstar 28i junior DHW problem

[Midge Gaunt]

Ok so I'll try keep this brief.
DHW is warm but never hot enough for a bath.
When you increase flow from tap, the boiler ramps up but water is still luke warm.
I've cleaned the primary exchanger with a good flush, nothing really came out, was quite clear.
I've changed the secondary plate exchanger for a new one, changed the entire flow sensor and housing as was leaking.
Changed DHW thermistor and cleaned the diverter valve. Water does not leak into CH when running hot water.
What am I missing?
It's almost like the flow to heat ratio is wrong, as the boiler increases output when the tap flow is increased but just not quite enough. It used to run perfect.

Amy ideas? Many thanks in advance.

Midge

 

[cross thread]

How water should raise 35 degrees with a flow of 11 litr per minute,what’s yours ?
Also check for a faulty mixer tap / shower valve passing cold into the hot.
One way to test this is isolate the boiler cold inlet and after a while no water should come out of the hot tap’s

 

[CBW]

Is the stepper motor moving fully?

 

[Midge Gaunt]

Hi thank you for the replies.

The stepper motor moves ok as far as I can see.
I can isolate any mixers or taps in the house at source (I plumber the house) so I will isolate all except one and test it, don't know why I didn't try that.
Flow rate I'm not sure, I will check and report back.
Not worked on a boiler in many years, but it's my dad's so can't leave it. Gave up on gas safe years ago so am a bit rusty.

Thanks for the help.

 

[Midge Gaunt]

Problem sorted!
It was the shower mixer tap in the bathroom.
It was old so after diagnosis I just changed the whole thing. Can't thank you enough for the help!

Cheers, Midge