Worcester Bosch 27 Ri only running at 7kw output

[ronco]

hi
Got a customer where installed above boiler 9months ago and has been working fine. They called complaining that the rads and hot water not getting very hot especially when both were on together.
Checked system and boiler and found after doing a gas rating check it was only running at 7kw, gas supply to boiler when running is 21mbar.
Called out Worcester under warrantee , they say boiler is fine, poor flow through heating system and cylinder is the cause.
Flow only reaches 50c and boiler runs with out stopping, no noise and system has a new 15/60 pump, and return pipe gets hot.
The boiler seems to be stuck in low rate, as 7kw is the lowest output setting on this boiler, 27kw maximum.
Worcester engineer was called back and says he has changed gas valve, heat exchanger, PCB, and thermostats ect with no effect.
any thought would be welcome
thanks

 

[ShaunCorbs]

did you power flush the system ?

 

[ronco]

yes power flushed when fitted, also fitted magna-clean.
original 15/50 pump was replaced with 15/60.
flushed system through again and cleaned magna-clean ( although wasn't dirty ) between the Worcester engineers visit

 

[ShaunCorbs]

yes power flushed when fitted, also fitted magna-clean.
original 15/50 pump was replaced with 15/60.
flushed system through again and cleaned magna-clean ( although wasn't dirty ) between the Worcester engineers visit

what did the pump look like?

 

[thompsonbrown]

If your gas registered inform Worcester of your gas valve fault and ask them to sort it out.

 

[gassafe]

Does it ramp up when placed in max on service mode?

 

[Dotty]

Right. Tmi for open forum.