When I bought my house with oil fired boiler and radiator heat, the system constantly became airbound. As long as it was cold and the boiler ran, it was OK. But if it got warm for a few days and the boiler didnt run I had to bleed the radiators. This ammounted to once a week. Sometimes every other day. The "pros" said leave it alone and just bleed it. Then I saw a friend install the same system in a house he bought that was electrically heated. The guy did the installation over the summer. I saw a widget on the boiler I didnt know what it was. He told me it was an automatic air bleeder. I found out I could get them in a size to replace the air chambers on my radiators. 11 in all. Also, I installed a diaphram type of expansion chamber to replace the old expansion tank.
It works great! No more problem. I wonder was installing the auto bleeders on each radiator overkill?
Gas, Oil, solar and renewable service and installation in Devon UK- Please note my advice is not based on USA regulations as I am UK resident. Therefore I will try to avoid posting where confusion may be caused or make that clear.
Over time auto bleeders are guaranteed to leak. In fact depending on the system and placement, can often let air in as system cools. Proper placement of one air eliminator near boiler, the bladder tank will help, but most importantly operating pressure and pump sizing and placement are critical to solving air problems.
I agree as to "why do you have air in the system"???? Once you fill a boiler system up you should not have air in the system ever again. In a perfect world anyway.
Don't patch the result fix the problem!
You solved the symptoms, now you have to find the disease and cure it. The most common source of air in radiators is a bad seal on the pump which is tight enough not to leak water, but does SUCK air in when the pump is running. The fact that the air vent on the boiler eliminated the air problem indicates that the air is getting into the system at, or before, the boiler. If your pump is on the return, or ahead of the air bleeder on the feed, that only reinforces that diagnosis.
I like to install one of these at the boiler it's called a spriovent and it does the job better than any other automatic vent.
quote Ignorance can be fixed. Stupid is forever
Or its sister axiom. If you think education is expensive, you should try illiteracy.