Constant Air In Towel Rail

5 Nov 2008
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United Kingdom

I have a Vaillant EcoTec 831 Combi, with 8 rads.
I seem to always get air in the towel rail which is the highest rad in the system.
If I run the heating for a few hours the towel rail will go warm then I have to bleed air out of it to get it red hot again.

The sealed system has a bottle of Fernox F1 which has been in for about 7 months.

Do I have a problem?
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Not necessarily a fault.The next time you have to bleed your towel rail hold an inverted glass to collect the gas that is vented, then try to light the gas.If it ignites then you have hydrogen forming in your systen and it may require a flush and the addition of some chemical treatment.I doubt that it's air as you have a sealed system and the internal pressure is above atmospheric.Make sure that you top up you system pressure after bleeding the rads.
Does the system pressure drop to zero when it cools down? If so, your expansion vessel may be flat as in tyre, or the diaphragm may be punctured.
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Do the hydrogen test as suggested earlier.If your system was brand new it may be disolved oxygen but you don't mention it as a new system.

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