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Discuss System sucking in air - suggested fix is convert to closed - looking for more info in the Central Heating Forum area at

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Hi everyone,

I'm a newbie here, a layperson homeowner, stopping by in desperation to try and get a better understanding of my options regarding a diagnosis.

I have a conventional gravity heating system (cold water tank).

British Gas put in a new boiler and replaced most of the other bits (pump, condenser, flue) back in 2011.

The current boiler is a Worcester Greenstar 18Ri.

Over the last few years I have had nothing but problems. First the pump became really noisy. Then the boiler kept getting a flashing light and turning off.

I have had the same heating engineers working on it for at least three years and have had done everything they said needed doing. I must've spent at least £2000 so far.

I've had the boiler serviced every year, the pump replaced twice, a full power flush, new 3 way valve, several new rads, a magnaclean, new programmer and finally a new condenser.

And yet, still the blasted boiler keeps turning off with a flashing blue light.

Now the engineer is saying that the issue is that the system is sucking in air because the original pump was installed with "not enough head room". Apparently the newer pump is more powerful and is now causing the sucking in of air.

Every time it has happened I have to wait for them to come out and get rid of the air at £90 plus VAT per time. Plus we are without heating for the whole time which is a major issue as my mother is 72 and a cold will put her in hospital.

We were desperate the last time and Coronavirus had just started so we got another guy out cause he could come quicker. He said the same thing. He bled the system, turned the pump down, showed us how to reset the boiler and told us to see how that went. He said if having the pump set lower didn't solve the issue then the best choice was to convert the system to a closed system. At a cost of at least £500 not including VAT.

And then of course Coronavirus hit properly. It's happened again twice in two days and now I'm stuck.

I've googled converting an open system to a closed system but I can't find anything about it except for the more modern Megaflo type setups.

I'm hoping someone here can maybe explain a bit more about it...?

What does not enough head room even mean?

Is converting the system really the only thing that can be done?

What's involved in a conversion?

What are the implications of converting it with regards to maintenance and servicing etc?

Neither of the current engineers are able/willing to explain any of this in laymans terms.

I'm sick of throwing money at this problem. Then next time I do I want to be sure it's going to be the last time for a good long while.

Can anyone help me understand? Any help would be greatly appreciated. I've got a bunch of photos of the setup.

Thanks for reading my post.


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