Furnace saga continues

I started a new thread on this because the old one was getting too long. You can get the background here:
http://groups.google.com/group/alt.home.repair/browse_thread/thread/52abfb9055f6267c/b8bd99bad0ef69ac?lnk=gst&q=coustanis&rnum=1#b8bd99bad0ef69ac0
http://groups.google.com/group/alt.home.repair/browse_thread/thread/6c6386e6d2177ea9/7039eff338195ed1?lnk=gst&q=coustanis&rnum=4#7039eff338195ed1
Ok, the room that has the radiator pipes in the concrete slab has been isolated and I put about 22 pounds of compressed air into it. After 4 or 5 days it had lost most of the pressure. In a day or so it will probably be empty. I assume then that there is a leak in that room unless there is some other furnace phenomenon that would cause a system to not hold compressed air. Since I don't see any water I assume it's in the concrete pad.
BUT...
The furnace it still losing pressure. Since all the pipes are either visible or within the walls if this wood and sheetrock house, I would assume that if there were an additional leak that I would see a wet wall, a puddle or water dripping from a ceiling. I see no water. Someone in a previous thread said it could be a bad expansion tank. The expansion tank is brand new and was installed after this pressure problem started. The auto feed valve is closed and has always been so, even when the system was not losing pressure. I'm not sure what to do next or what to check. I can isolate another loop but I'm wondering if it's a leak at all in this part. Does anyone have any ideas?
Thanks for all the help so far.
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coustanis wrote:

http://groups.google.com/group/alt.home.repair/browse_thread/thread/52abfb9055f6267c/b8bd99bad0ef69ac?lnk=gst&q=coustanis&rnum=1#b8bd99bad0ef69ac0
http://groups.google.com/group/alt.home.repair/browse_thread/thread/6c6386e6d2177ea9/7039eff338195ed1?lnk=gst&q=coustanis&rnum=4#7039eff338195ed1
This may verge on the drastic level, but consider draining the system until just the boiler is full (all piping empty).
Then pressurize the piping (and the boiler) with air. Run it up to 30 psi. Over a couple of days you should be able to get a feel for how much air is lost (or not). Even a chance you could hear the air whistling out.
If it does lose pressure but you can't find where, consider adding mercaptan to the compressed air so you can smell the leak.
Jim
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Your connectors or your valve may have a leak also. Check them with a bubble solution to be sure they are not part of the problem.

You don't have a furnace, you have a boiler. Furnaces heat air, boilers heat water.

You are probably correct.

At least twice I've suggested you leave the valve open to be sure all the air is purged. Have you tried that? Seems as though no. Another poster, hvacmedic, also stated the valve should be open and gave a detailed reasoning behind it all. Listen to the pro.
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I believe it will overpressure if I do that but I will do it tonight. If it over pressures I'll replace the auto fill valve and let you know what happens. I'll also get some detergent / water mix and check the connectors. Thank you for the suggestions. I do appreciate it.
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A couple of weeks ago, either you or hvacmedic suggested a web site. I looked for the thread but I guess it expired. Would you mind listing it again? I could google but I want the one you mentioned. It's probably a good site. I want to read up on proper setup of the auto fill valve and air purge valve. For example, should the red cap on the air purge valve be open or closed. I've kept it open so air can escape.
I know I'm probably getting teadious for you by now. Thanks for your patience.
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My plan for today is to set up the system properly. To me that means:
Open the auto fill valve and check that it adds and closes at proper pressure. Replace if necessary. It has a slide handle on the side and a locking screw adjustment on the top. I have no idea how to balance these out. I'll google but it's hasn't been much help. My assumption is that the slider handle stays all the way open and I adjust the open / close point with the screw on top. I'm sure it's out of adjustment because the screw turns somewhat freely. It wasn't locked.
Pressurize the expansion tank to equal boiler pressure. I'll have to go get another pressure gauge. My tire gauge doesn't read low enough.
Set up the auto air purge valve. Is the red knob (escape vent) left open or closed. If open, I can hear air hissing either in or out depending on if I am adding or removing water from the boiler. If closed, will it purge?
I will continue to google this stuff but so far all I get is people trying to sell me things.
Again, I appreciate your patience. If you ever get to Maryland, I'll buy you a beer or 6.
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I took off work today to mess with this.
I replaced the boiler feed valve. The old one had the adjustment screw loose and it was easier to spend 40 bucks on a new one that was factory set. When I took the old one off I saw that it was heavily damaged by electrolysis. Some of it's internal parts fell out through the fitting holes. After install I left the new one in the auto position with the isolation valve open as was suggested.
I verified that the expansion tank was good by checking that air, not water came out of the snifter valve and that it's pressure equaled the boiler pressure.
I isolated the entire second floor of the house by cutting and capping. I know this sounds extreme but it only required two cuts and two caps. Total time for that was 10 minutes and 3 bucks. This allows me to have no pipe connected to the boiler except what I can directly see.
Closed the air purge valve at the top of the system.
I filled he system to 20 psi. The feed valve kicks in at 12 psi. If it maintains 20 then I fixed it. If it drops to and holds 12 then I assume I still have a leak somewhere although I can't imaging I have a leak that I can't see, at this point.
Nothing to do now but wait a week and see what happens.
Look folks, I know I've been a pain in the ass with this. I get that way when confronted with expensive things I don't understand. I learned a lot and saved a pile of money. I needed to learn this system. I couldn't go and spend a hundred bucks an hour every time the system burped or did some weird thing.
I do appreciate the patience and the advice. The offer for beer still stands.
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Which doesn't change the fact that I have a leak in the pipe under the concrete slab but, that's a separate issue I'll deal with that later, after I get the main system set up properly.
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If the valve was not part of hte problem, it certainly was ready to fail. Smart move to replace it now.

Is al lthe air purged?

Real beer, none of that "lite" crap. We don't drink cheap beer either.
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Probably not. I'll purge it manually every day or or so until no more air escapes.

Not a problem. I'll go as heavy as you like. And as much as you like.
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coustanis wrote:

http://groups.google.com/group/alt.home.repair/browse_thread/thread/52abfb9055f6267c/b8bd99bad0ef69ac?lnk=gst&q=coustanis&rnum=1#b8bd99bad0ef69ac0
http://groups.google.com/group/alt.home.repair/browse_thread/thread/6c6386e6d2177ea9/7039eff338195ed1?lnk=gst&q=coustanis&rnum=4#7039eff338195ed1
Just out of curiosity, did you blow (or suck with a shopvac) the water out of that loop before you pressurized it?
If not try doing so and see if your leakdown rate increases because air can escape through a leak faster than water can be pushed out by air, and you might, just might, be able to hear it hissing out.
It does sound like your worst fears will be realized and the leak is buried under the concrete floor, so you'll have to replace the piping with some above slab stuff.
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat \'57 EE)
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