Radiators sucking air, over added water, drained tank, now no heat

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Old 12-27-10, 04:54 PM
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Radiators sucking air, over added water, drained tank, now no heat

Hi forum: I'm new here, and may have gotten myself into some hot water - so to speak... I started by simply wanting to bleed my radiators, in a 2 story house, plus basement. Boiler in the basement is an old Hydrotherm with an expansion tank above it in the ceiling.

I ground floor was fine. Upstairs, I was getting only air, no water. The air would peter out till there was no more pressure. Then I noticed that they were sucking air in. So, I added water to the system and kept running up and down to bleed and add more water. Then I read advice to another diy-er re pumping up the pressure to 20psi or so - and I did that and finally got a good flow going in all radiators. I balanced the pressure by releasing some water from the faucet at the bottom of the boiler and got it down to about 12-14psi cold. When I turned up the heat, I got great heat in every room. But, the pressure really rose - and water came out of the pressure release valve/hose (at least that works...). I kept draining water out of the bottom of the boiler, seemed to get it at a good psi (12-15) - but the pressure kept rising with the heat on - and flipping the pressure valve.

A heating guy told me that the expansion tank should be empty and suggested I drain it completely. So, I took about 5 gallons out of there.

Now, I have no heat. And the boiler doesnt seem to come on at all.

Can I be helped? Thanks so much! -diywannabe in DC
 
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Old 12-27-10, 05:19 PM
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Your conventional expansion tank is water-logged. It will have to be drepressurized and drained until air is freely sucked in and the tank is full of air. The procedure depends upon your valving. But to further advise you, we need photos of your system. http://forum.doityourself.com/electr...your-post.html

If, as I suspect, the tank is water-logged, your draining 5 gal of water from it wouldn't help - if anything, probably make it worse.

Why did you start all this by bleeding air? What was the problem?
 
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Old 12-27-10, 11:25 PM
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Hi Speed 30 - Thanks so much for replying. The original problem was that the second floor wasn't getting much heat. So, I was just trying to bleed the radiators and only got air, then nothing, and some sucking air in. So, I was adding water to increase the pressure. But after I bled the radiators, pressure was too high and I couldn't seem to find the equilibrium to get a safe consistent pressure in there while it was hot and cold.

Space is quite tight, but I'll do my best to post some pictures. Here's what I was able to get - hope this helps: Flickr: reisendorf's Photostream

Thanks! - r
 
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Old 12-28-10, 08:44 AM
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You have a valve in the line leading to the bottom connection to the expansion tank. Here's the drill:

Turn off the power to the boiler, and cool the system down to 100 deg or so.
Shut that valve.
Drain the expansion tank from its drain valve until air is sucked into the tank and it is completely empty.
Open the valve and adjust the system pressure to 12-15 psi. Turn the power on.

Happy New Year.
 
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Old 12-28-10, 09:17 AM
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Thanks Speed. I did the drill - drained the expansion tank till I got just a drip. Shut the drain valve. Then turned the fill valve to the expansion tank back on. But, the pressure now reads 22psi. And when i put the boiler back on, it started to rise, so I shut it off again. Isn't the valve to the expansion tank supposed to stay open at all times? It was open before I started fiddling with it. Or are you suggesting that that valve is closed after I reach 12psi? Also, if its 12psi cold, will that rise when the heat is on? Thanks again! (its 58 degrees and dropping in here... so very much appreciate the help).
 
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Old 12-28-10, 10:15 AM
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Originally Posted by diywannabe202 View Post
I did the drill - drained the expansion tank till I got just a drip.
You have to drain until you hear air replacing the last bit of water - glub, glub, glub. The tank can form a vacuum preventing air from going out. Then shut the drain valve and re-open the shut-off valve below the tank. If you drain through a hose, it might not drain completely - drain directly into an open bucket.

The valve below the tank is to be shut only during the draining process - at all other times, it must be open.

If the tank is completely drained and full of air, and the cold temp at about 12 psi, then the pressure hot should be less than 20, more like 16 psi.
 
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Old 12-28-10, 11:22 AM
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mastertech

ok Im assuming this is a hot water boiler.The expansion tank above the boiler is to allow the boiler to breath basically. The boiler strictly circulates the hot water throughout your system to give you a radiant heat.The boiler s biggest problem you will have is air trapping in the system.each radiator should have a bleed off either a manual or a auto air bleedoff.It also is good to have a bleed-off at the highest point of your system.The air will trap right there.You made comment of some radiators not heating up,well an old trick to get rid of air is to cycle the circulating water pump off and on,This will allow the air pockets to move along inside the system.once the air is removed,the radiators should all be heating up with no problems.Your expansion tank also will allow air to trap in it as well.You dont want the exp. tank to fill up and give you a water logged condition.The whole point Im trying to make here is where the water is supplying the boiler,well those are usually preset at a certain pressure for your boiler system.If the boiler keeps water-logging and filling your tank ,that valve may not be shutting down for you automatically to maintain the pressure on your system.The valve may be trickling into the boiler to cause it to run at a higher pressure.
 
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Old 12-28-10, 01:15 PM
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Thank you Speed30 and Mastertech! I think this did it. I drained the expansion tank COMPLETELY. Gurgled for about 20 minutes until there was nothing left at all. Then, I closed the drain valve and opened up the fill valve. And the pressure went from like 0 to 9. Now, its stable at 10psi and its been running for the past hour. I checked all the radiators and drained the tiny amount of air that was still in them and alls well. Is 10psi enough pressure? You think the job is done? Any reason to have a pro check it out? Thanks so much for the great advice. Seems like the full drain was the key! -r
 
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Old 12-28-10, 03:26 PM
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The pressure should be at least 12 PSI when COLD, and it should increase when hot, maybe as high as 20 PSI... but DON'T TRUST THE BOILER GAUGE!

If you don't have enough pressure in the system, you will have the same problem with the 2nd floor not getting heat eventually.

Try adding about 5 more PSI to the system and see how that goes.
 
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Old 12-28-10, 04:41 PM
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Hi Trooper - thanks for the input. I'm getting good heat upstairs, right to the top of all the radiators. So, no need to do anything, right? If I do have to increase the pressure, how do I do that? This is what got me in trouble to begin with. I had it at about 12 cold, but it was going up to 40 hot. Thanks. -r
 
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Old 12-28-10, 05:48 PM
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If you were to want to do anything at this point, the first step would be to verify that your pressure gauge ain't lying to you... they do that often.

If it was going to FORTY hot, it's almost a sure bet that your gauge is off... if that's how high it went before the relief valve opened, I would trust the relief valve... which is at 30... but given the uncertainty, I would do some checking.

First, if the relief valve is over five years old, simply replace it first chance you get.

Next, if you can find a 0-30 or 0-50 PSI gauge at a plumbing or pool supply (don't bet on HD or Lowes having them, but they might), you can make adapter to go on one of the boiler drains. Screw gauge on drain, open drain, read pressure, close drain.

HD or Lowe's may have these in the lawn sprinkler section:


image courtesy plumbersurplus.com

The gauge that comes with it is useless for low pressure work, so remove that gauge and install the lower pressure one... these go for about $10 around here.

Does your system have a PRESSURE REDUCING VALVE that automatically fills the system?
 
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Old 12-28-10, 09:57 PM
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Thanks Trooper. Its been flipping the relief valve pretty consistently when hot and releasing a gush of water each time. And just this morning was dripping when it reached around 30 cold. (That was before I flushed the expansion tank again). I'll work on getting another test gauge though.

I do see what looks like a pressure reducing valve attached to the back of the boiler - looks like this but old and a bit of corrosion on the outside:


image courtesy tanklesswaterheatersdirect.com

If I do need to add pressure, is it by adding water with the water valve that feeds to the boiler?

Thanks for all the great help from you and all the other experts out there! - r
 

Last edited by NJT; 12-29-10 at 09:51 AM.
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Old 12-29-10, 06:23 AM
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While you are looking for gauge parts, also pick up a new pressure relief valve. Once they blow a few times they tend not to hold as well.

Yes that's how you add water, with the pressure reducing/fill valve.
 
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Old 12-29-10, 10:00 AM
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Let's recap...

You fully drained the expansion tank, and everything was fine... for a time ?

You should not need to drain the expansion tank again, it can't possibly lose it's air cushion in a day or three... so save your trouble there...

You are saying now that the pressure relief is still opening? at 30 PSI on the gauge?

I'm with Xiphias, replace the RELIEF valve.

I suspect that the reason that the pressure is now going too high is because the (pictured) REDUCING valve is leaking through.

There must be a 'shutoff' valve upstream of that reducing valve.

AS A TEST, let the boiler get cold. Drain pressure from a boiler drain until you are at 12-15 PSI. NOW CLOSE THAT SHUTOFF VALVE that feeds water to the boiler. MONITOR the system for a few days and watch the pressure gauge. If everything is now stable, you probably will also need to replace the REDUCING valve ...
 
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Old 12-30-10, 06:00 AM
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Hi All: Some of this is out of order.

I did drain the expansion tank twice - but first time I stopped while it was still gurgling. The second time I left the hose in place until it was 100% drained.

After that, everything has been working fine for a couple of days with no spiking of the pressure and no opening of the relief valve. But, the pressure appears to be slowly rising. After the 2nd drain, it was at 10psi. But over the past 2 days, has been rising slowly - and now is all the way up to 29psi.

Unfortunately, I'm hanging up my wrench for now. This is a rental and I've put the call in with a service co to take care of it from here. I can open and close some valves, but when I need to start replacing parts, time for me to call the pros. (On the house I own, that's another story - and may have to be back soon for that one.)

I presume they will replace many of the components recommended and more - like the expansion tank too to the more modern type.

Again, I appreciate the amazingly professional advice I've gotten here. I've never seen anything like this, with such advice at your fingertips. It is so tough to find pros with the patience to fix these old houses - seems they quickly jump to replacement. Thanks so much! -r
 
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Old 12-30-10, 09:08 AM
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This is a rental
And as such, you should have told us that heads up... and we would have told you never to even take the wrench off the hook... the equipment isn't yours, and you should not have touched it in the first place.

Good Luck! (and don't tell the management that you messed with it...)
 
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Old 12-30-10, 12:56 PM
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I believe he owns the property and rents it out.
 
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Old 12-30-10, 04:04 PM
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Why do you believe that Droo?
 
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