Problems with Central Heating system.

[Peter James]

I de-aired the Central Heating system today, a thing I need to do about once a month. I did so from the towel rail in the bathroom, the highest point in the system.

Following a suggestion from someone on this NG I lit the escaping air with a match as the air was flowing out following the loosening of the drain screw. It lit up like a gas welding torch and caused me to all but jump out of my underpants.

Is there an expert on this NG who can tell me what this would indicate? And any cure for the constant need to de-air the system.

The system is 20 years old from new, but with a new Worcester Bosch Greenstar

25i boiler that is one year old. Peter

[newshound]

It means you are collecting hydrogen in there. So, you are corroding steel. That might mean that the inhibitor is depleted.

Do you need to repressurise frequently? That would mean you either have a leak or that you are expelling water from the relief valve (perhaps because the expansion vessel has failed, although that is less likely on a one year old system).

[Tim Lamb]

In message [e-mail]>, Peter James [e-mail] writes

An expert will be along shortly but meanwhile.. Hydrogen is what is left after internal radiator rusting has removed the O2.

System needs topping up with anti-corrosion fluid.

[Harry Bloomfield, Esq.]

Tim Lamb formulated the question :

'Inhibitor'!

If the system is rusting the likely the water will be filled with debris too. Time for a thorough flush out, or maybe even a power flush, a refill then the inhibitor.

[Roger Mills]

As others have said, it's hydrogen - which indicates corrosion.

But if you had a new boiler a year ago, didn't the installer do a system flush and then add inhibitor? If that had been properly, you shouldn't have this problem after only a year.

Is it a vented primary system, or is it pressurised? If the former, it could be leaking and introducing fresh oxygen in the top-up water. Or it could be pumping over and introducing air. If the latter, there could be a problem with the pressure vessel. In this case, you would be aware of having to re-pressurise it frequently.

[Fredxx]

Pump over would aerate/oxygenate the water and the last gas I would expect to come out of a vent would be hydrogen.

I would also suggest adding inhibitor pretty smartish, perhaps by adding a magnetic trap if the system doesn't already have one and filling through that if the system is unvented.

[Roger Mills]

Yebbut - the oxygen would encourage corrosion which, in turn, would produce hydrogen.

Agreed.