sime 90 combiboiler no c/heating

[oldboy]

I can get hot water but no centeral heating.
I have bled all the radiaters.The water pressure is 1 bar
The pump sounds as if it is turning, and it gets hot with the temperature rising on the dial, but the radiaters stay cold.
The heating worked fine in the winter, but I have just drained the system to fit a new radiater, could there be an airlock?

 

[Agile]

I think you may have missed a word out of the boiler model name.

It sounds as if the diverter valve is jammed or stuck or the actuator is failed ( if its the model with an actuator ).

Tony

 

[oldboy]

Hi
thank you for the reply. The boiler is a SIME super 90 plus. why I think that it might be air in the system is that the hot water is ok but the c/h does not fire up, as if there is an airlock, but i am probale wronge.

 

[Agile]

It does sound suspicious.

Have you left one of the isolating valves under the boiler closed? Please check whatever you think!

You say the pressure is 1 Bar but did the gauge go to zero and did you increase it to 1 Bar?

I suggest you increase it to 1.5 Bar. Presumably you have bled the air out of the refitted rad?

Tony

 

[oldboy]

Hi Tony
I did not close any of the isolating valves, but drained the system through a radiater drain plug, so the system was dry. I then filled the system up to 1 bar, but maybe I did it too fast. I will drain the system again and fill it slowly to 1.5 bar. I will let you know the result. Thanks again for you help.

Roy

 

[Agile]

No dont drain it yet again!

I have seen this several times where DIYers want to drain a system again.

Thats the last thing you should do.

Just repressurise it to 1.5 Bar.

There is a possibility that the AAV in the boiler is not operating or the pump has not been bled of all the air.

Tony

 

[oldboy]

Too late I'm afraid. I did drain the system, and refilled slowely to 1.5 bar.
The heating system still does not work. What happens is that the c/h burner ignites sometimes, the temperature goes up to about 50, there is LOTS of banging in the boiler and the pilet light goes out, The other thing that happens is that allthough the pump is working there is no heat transfere to the nearest radiater, The boiler starts no problem for hot water.
Roy

 

[Agile]

It still sounds as if the diverter valve is jammed in the DHW position.

Tony

 

[oldboy]

Hi Tony

WelL, I have got the heating working again. I went back over everything that you had mentioned about what the problem could be. It was an isolation valve to the boiler that I had left closed, and I can not remember shutting it off. It just goes to show that one must check every thing, because the brain plays tricks. Thank you again for all your help in resolving my problem

Roy

 

[Agile]

It does sound suspicious.

Have you left one of the isolating valves under the boiler closed?

Please check whatever you think!

Tony

That why I said exactly that three days ago.

Unfortunately in spite of me saying "please check it whatever you think" it has taken you three days to check it.

Thats why women are so good at finding boiler faults. They look at the simple things first.

Anyway I am pleased that at last you have followed my advice and got it working again.

Tony