Bleeding hotwater radiators - Conflicting Instructions


T

thekmanrocks

There are many well-intentioned articles on how to bleed your basic hot water radiator heating network.

Most recommend bleeding when system is *relatively* cool(is off or hasn't fired in a while).

Where they differ most is the starting point. Some suggest moving from radiators closest to boiler(1st floor) to the farthest(IE 2nd flr). This site - http://www.ehow.com/how_6382979_do-air-out-heating-pipes_.html suggests the opposite!

Does it matter?

Also, I was told that after a good bleed job none of my radiators should ring like bells when knocked on with my fist. Some of mine do, even though they are evenly heated side-side and top-bottom. Does that indicate trapped air bubbles?

And how do I remedy those?
 
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T

TimR

There are many well-intentioned articles on how to bleed your basic hot water radiator heating network.



Most recommend bleeding when system is *relatively* cool(is off or hasn't fired in a while).
You want to bleed when the pump is not running. Moving water can keep the air away from your bleed points. So turn off the system or just the pump if you have that option.

Then, bleed from high points first, because you're likely to get more air out faster. But with the water not moving, it probably doesn't matter much.

You'll need to restart the pump and repeat the process several times, because there's always a little air trapped in low points.

But don't bleed more water than necessary. Any water you release will be replaced from the makeup valve, and some air will come in with it, so you're fighting yourself.

In theory it should be better to bleed when warm, because warm water dissolves less air than cold. But I suspect the difference is not enough to make much difference. The air that is causing problems is mostly not dissolved anyway.

As far as ringing like a bell, I can't imagine a system with enough air to affect that still working.
 
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