Baseboard heat - auto vent? valve replacement

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Old 08-13-14, 05:52 PM
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Baseboard heat - auto vent? valve replacement

Hello.

I'm remodeling my kitchen and in the attic above the kitchen, on the baseboard pipes (which run through the attic to the bedrooms) is a Maid-O-Mist No. 66 Auto Vent (see images below, linked to Dropbox, I can't get them to upload here). It is clearly in need of replacement and I'd like to replace it now that I have easy access.

My question is is this the correct placement of this vent and is this the correct type of vent? Just about everything in this house was done incorrectly so I thought I'd check on this before I just swap it out.

Thank you

Image 1: https://www.dropbox.com/s/61mggaz763...812_081253.jpg
Image 2: https://www.dropbox.com/s/mflq3zoudv...813_204211.jpg
Image 3: https://www.dropbox.com/s/6j6h55smgc...813_204231.jpg
 
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Old 08-13-14, 06:09 PM
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If you have a conventional steel expansion tank (hanging up from the joists in the basement), you do not want any such air eliminators. If you have a bladder-type tank (looks like a propane cylinder), then, yes, you need a maid-o-mist, or equal.

From your photos, it's hard to tell exactly what has been leaking - the maid-o-mist or its connections.
 
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Old 08-13-14, 07:05 PM
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I have the bladder type tank. The maid o mist itself is leaking.

Does it need to stay in that spot or can I move it to more accessible location?
 
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Old 08-13-14, 08:12 PM
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Are you saying that there was no access to this attic space at all previously? and that there will not be when the remodel if completed?

No, in that case you don't want that there at all.

What kind of air elimination is at the boiler itself? THAT is where the vents need to be.

I can't believe you never had trouble with those pipes freezing.
 
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Old 08-14-14, 03:52 AM
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There is access to it but it's very difficult to get to. The boiler itself has a pressure relief valve, but the maid o mist is the only thing on the actual baseboard pipes for that zone.

We've only been in this house about 9 months, last winter was just about the coldest one I've ever experienced and the pipes didn't freeze, but then again this house is so drafty the boiler ran almost constantly.

So what is the proper placement of this vent? Supply line or return line? Very close to the boiler?

Thanks
 
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Old 08-14-14, 09:15 AM
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Well... there's a number of answers to that... " What's proper ... " is always debatable.

First though, let's talk about what that thing is actually capable of doing.

It is NOT capable of 'catching' air bubbles that are flying past it in a stream of flowing water.

If it's location is such that it's at a high point in the piping, and all piping slopes upward toward it, it MAY succeed in removing SOME air from the system on occasion. In other words, the only air that device will remove is that which can 'float' up under it when the water is NOT circulating.

Depending on some various factors, placing automatic air vents at the high points in a system can at times actually draw air INTO the system.

And they ALWAYS EVENTUALLY LEAK.

In order for that device to work properly it is mandatory that it is installed either on top of a properly placed AIR SCOOP, or on top of the boiler on a tapping that the boiler manufacturer has designed for the purpose.

Can you show us pictures of the boiler and associated piping around it?
 
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Old 08-14-14, 09:58 AM
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I'll get some photos of the boiler when I get home. It's very old and will be replaced this spring, I don't think there are any unused ports on it though.

The auto vent is about 20 feet (of pipe) from the boiler on the supply pipe, and it is a high point.

After replacing it (as well as a section of the base board) I assume the line will need to be purged of air. Is this correct? Is this done at the boiler or from the auto vent?
 
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