We have old and largely past it central heating system which I am loathe to replace because I think we'll shortly be selling the house. However, one of the radiators has always required bleeding. The pipework is microbore, and all of the radiators are what I understand to be double entry valves - that is, they have two pipes entering from one end.
My thoughts are that there is a loose connection on a radiator valve, a pinhole in a radiator or a leaking pipe somewhere, but consulting a couple of heating engineers has yielded no useful information. I wonder if anyone has any ideas? I have assumed that the leak must be between the radiator and it's immediate predecessor on the circuit otherwise the air would just accumulate in the previous rad?
Second query: what size of boiler in BTU would you expect to see in a large 4 bedroomed house?
On many old sytems there is just one rad which collects all the surplus air in the system. Various theories can be advanced such as this is where the water slows down and releases disolved air. None are over convincing. I take the line that this is something which just happens. Air gets into the system via the feed and expansion tank, minute leaks at the valves etc. Some of the internal corrosion in the rad will also produce air. Provided none of the rads are leaking water, I would leave alone beyond regular bleeding.
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