Does baseboard piping need an airvent at the top of the system?


Old 12-29-13, 06:26 AM
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Does baseboard piping need an airvent at the top of the system?

I noticed people have air bleeders on their radiators but I don't have any on my baseboard.

I have one taco auto air vent on the fresh water supply side of my boiler.

I have a two story, two zone house where the boiler is in the basement.

If air moves to the top, would it make sense to add at least one air vent on the second floor? Would I add it to the supply side or return side of the loop?
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Old 12-29-13, 08:38 AM
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Air vent is not needed... If you have air upstairs you have another issue...

Low pressure in the boiler.
Current air vent not working

Take a pic. Is the current air vent attached to an air scoop?

I assume you have a bladder type expansion tank?

Whats the make and model of the boiler?

What does the boiler gauge read? Temp and pressure?
Old 12-29-13, 08:40 AM
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Hi M3at...

IMHO, it's never a bad idea to have MANUAL bleeders at the top of a heating system. Even the AUTOMATIC FLOAT TYPE are OK, but only as long as when not in use the vent caps on top are kept CLOSED during 'normal' operation.

Vents at the top of system are very handy when initially filling, or refilling after service, because as the system is filled with water, the air can be released at the top, rather than having to force it back down by pump or purge.

The reason I say auto vents are OK if kept CLOSED when not being used to fill or refill is because eventually they will LEAK... it's a fact of life... and since they are often hidden away where they can't be seen, and usually leak slowly, by the time the leaking is discovered, damage can have occurred... wood rot, damaged carpeting, mold, etc.

Do not be tempted to use the ones they claim as having any kind of cellulose 'disc' inside... those are the worst!

I believe that the best place for any kind of high bleeder is at a DOWNSTREAM point in the piping where the flow turns DOWN on an elbow.

Another reason to not use auto-vents at high points is because under certain conditions they can actually SUCK AIR IN. If system pressure is low for example, the top of the system can actually be BELOW atmospheric pressure, and the vent will suck. Sometimes when a pump starts up the pressure at the top of a system can momentarily drop below atmospheric... vent will 'gulp' air.

I have one taco auto air vent on the fresh water supply side of my boiler.
I think you've posted pics of this... but I'm not sure what you mean by 'fresh water supply side' ?

MOST air vents I've seen installed on systems are in totally useless positions on the piping. Seems guys just stick them anywhere sometimes. Fact is that the vent will only collect any air and do any good if it's located at a spot where air bubbles will naturally float up under the vent.

An IDEALLY piped system will need only ONE air vent. This vent will be located on a properly installed air scoop (or be part of a 'micro-bubble' type of integrated scoop and vent, such as the SpiroVent type.) The expansion tank on this system will be hanging from the bottom of this scoop, and the pump will be 'pumping away' from the scoop... and this setup preferably on the HOT SUPPLY OUT of the boiler.

With the above setup, there will be little to no chance that air will collect in the high loops and will be efficiently eliminated from the system by the single, properly positioned, air vent and scoop.

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