Main Combi HE needing high flow rate to trigger DHW

[virgil]

Hi everyone - not been on here in ages, but know someone will have some sound advice

My Mother has just had her Main Combi 30 HE serviced by her regular guy - Expansion vessel needed recharging and all seem well but after he left I found there was no hot water unless the taps were turned fully on, and the shower head needed removing to allow a high enough flow rate to trigger the DHW.

Had it looked at again and the Flow 'switch' cleaned out (hard water area) and I had the diaphragm replaced just because he was 'in there' and seems a little better, but we still need to turn the taps on more than seems normal. Manual says DHW at a minimum of 2.5l/m but requires 4l/m to fire the boiler for DHW.

As with all these things we didn't have measurements from before...it just seems the tap rates need to be excessively high to fire the DHW...

Plumbers we've had say its as good as it gets....

Any thoughts??

Thanks

 

[Chriswareham]

when you turn on the hot water dose the pin move out to activate the miroswich?
doses the heating come on when the hot water is call for? run hot water with heating cold dose the flow on heating get hot

 

[Chriswareham]

make sure that the micro swich is not loose