Central heating overheat

[Chris999]

I have a floor standing oil boiler (Worcester). Header tank in attic.
The overheat cut out was turning off the boiler.
The CH engineer has replaced the solenoid, heat sensor and electronic control. he cited failure of the solenoid.
Now the system is overheating, turning down the boiler thermostat seems to cut off the burners, but the CH system still gets too hot . The domestic hot water heats correctly. tank stat set at 60
The header tank also gets hot, there is a 9" space between water level and overflow pipe.
I drained some water out of the rad and it was black but not sludge , that I could see.
I did wonder if the symptoms had been fixed but not the problem in other words was there an original overheat problem that caused the solenoid to fail?
Anyone have any ideas that might help?

 

[twgas]

Sounds as though you've got asystem fault rather than a boiler problem. Black water indicates sludge, blockage, pump (due to sludge build up) failure etc.

 

[Agile]

I nreally wonder if he has done the right thing!

Slowly drain off some water whilst operating the CH until it runs clearish. At a drain rate of 2-3 li/min that can take an hour or two. ( Dynamic draining ).

Then add some Sentinel X800 to the header tank and then run off about 10 litres whilst running the CH ( to ensure it gets from the F&E tank into the system.

Run the system for about 10 hours on heating and then repeat the dynamic draining until it runs clear.

Hopefully that may clear some of the sludge in the system and might have made an effect on the symptoms.

Tony

 

[Chris999]

Thanks for the info.
So the money is on sludge not a boiler fault.
Is it worth getting the Boiler thermostat checked?
Chris