Let's say you have 12psi in you system. That gives you 27.72 feet of head. Unless those baseboard tee's are high than that and leaking, you won't suck air.
Originally Posted by Equito
What i'm saying is your getting air in the system. Unless any components is above 28 feet, assuming your system is at 12psi or greater, you are going to leak water not suck air into the system. So the only other way air gets in the system is from makeup water or osmosis through the walls of the non ferrous components of the system. With half way descent air elimanator the osmosis is no problem. But with sustain makeup water, lots of time the air elimanation can't keep up. The oxygen will go to the highest point of the system. If that highest point of the system isn't run through the air elimination it will slow act like a air custion and prevent the water regulator from filling, hence the pressure is ok.
I hope you are following this. lol
Except for the "feet of head" construct, I think I understood all of that. Thanks. While the BB ts are not 27 feet higher than the furnace, they are about 6 ft higher, and 20-40 feet away from the furnace - but whether that makes a difference, I don't know.
Originally Posted by ascj
The system seems to maintain 18-20 psi at rest, and pops to 21-22 while operating. Right now, for example, the burner/pump have been off almost an hour, the boiler's at 130 F. and the pressure's at 20.5. If it doesn't seem to ever drop anywhere near 12 psi, never mind below it, does that suggest there is no leak? Or only that the make-up system is keeping the psi up?
The most knowledgeable tech (the one that figured out that running the upstairs baseboards would flush out the air and stop the Low Water Cut-off from cycling the burner on/off) had a light bulb go off when he heard we hardly ever used the upstairs baseboard heaters. In his opinion, the simple lack of use caused the condition, and not some defect in the system. He didn't seem to think it was unusual, in other words.
I appreciate the explanation and input. Any new thoughts are appreciated.
Air is getting into your system, some how.
And not using the upstairs, isn't causing you to have air issues at the boiler.
Tell them to do a proper check on your expansion tank.
As Beenthere stated, lack of use doesn't cause air to accumilate in the system. With the pressures you stated, there is also, no way of the system to suck air through a leak. So the only thing I can see, is there is a leak you can't see, that is bringing in an excessive about of makeup water(oxygen bound) in a system that can't get rid of it. And from the pictures, it looks like the only place you can't see a leak is the concrete floor tubing. Does concrete causing copper to leak, NO. But some ingredients in the concrete can. Also when tubing can't expand properly, it with cause leaks.
i thought the extrols were supposed to be mounted upright. anyone know if that's the case?
I have never heard that. The only issue I have found with them mounted horizontally, is it puts alot of stress at the 1/2" coneection without the tank being supported properly.
Originally Posted by fenian
Extrols should be mounted with their connection pointed up. By positioning the tank in this way any air that might get to the tank will migrate back out to the system and be expelled as it should be.
With an automatic water make up any leak that might be in the system will not show up, because as soon as any water leaks out it's replaced with fresh water.
Only system I ever saw that "generated" it's own air/gas was an aluminum block boiler that had improper antifreeze installed in the system. Something in the makeup of the antifreeze was interacting with the aluminum and was creating a gas inside the system. I don't believe your system contains anything that would cause this.
The other conditions that can cause air to become loose in an otherwise sealed system is actual boiling of the water in the boiler itself. This can be caused by low water flow through the boiler, not enough pressure being maintained (don't always believe what the pressure guage says) or blocked passages can cause to much heat/btu's to be delivered to the water side (in small concentrated areas) causing the temperature of the metal in contact with the water to cause surface boiling even at correct pressures.
Air isn't magic. It's either being generated, interjected or pulled into the system. Trick is finding out which.
Use the biggest hammer you like, pounding a square peg into a round hole does not equal a proper fit.
For this furnace owner, the real trick is finding a tech who's expert with these systems. Thanks for the input - the Extrol mounting attitude was news to me. See http://nspgweb.com/ads/graphics/281AM0334_642031.pdf at very bottom-left of p. 3.
Originally Posted by firecontrol
Getting too technical for the open forums.