hot water heating

[saccounty]

I have a hot water boiler used for heating a building it is popping off on the saftey which is 30psi. Boiler is 14psi when cold. I checked the expansion tank cold it is 12 psi. Boiler operating temp. is 160degerees. I have drained the boiler and refilled making sure there was no air left in system and the air vent is working and is at the highest point in system. I replaced the pressure regulator on the feed water line thinking that it might be leaking by when the system is off but did not have any effect. it is set at 12psi also. Any ideas where to look at next.

[fishface]

What kind of expansion tank is it? If it has a bladder in it check to see if the bladder has not broken. If it is broken the whole tank will be full of water. If it is an old style with no bladder check if it is water logged. If it is, isolate the tank from the system and drain out the water then refill the system.

[simpleman]

And dont be surpise the tank could be to small,Lots of
not size properly tanks out there.

[saccounty]

thank you for your replies. The expansion tank does have a bladder and there is no water in the sight glass, also it does have a valve to check air pressure which is where I am reading the 12psi. I don't suspect it is the wrong size because it has worked for many years like it is, wth no problem. Do you know how to size them I could look into that.

[airworx]

are you using the quick fill valve to fill the system.
expansion tank should have half a sight glass full of water.
i would check to see if the tank fitting is stopped up and also check the pressure reducing station to see if it is set properly or if it is even working.
most prv,s are 12 to 15 #s. you ar popping off because you are over filling and tank valve is probably stopped up.
expansion tank is ok i would think by your remarks.

[Diceman]

So what is the pressure when it gets hot? Over 30 lbs on a reliable gage? Could be a bad relief valve, I change lots of them, they get all gummed up with crap.

[saccounty]

thanks airworx and diceman I am using the quickfill valve to fill system and the expansion tank only has a sightglass to see if the bladder broke I assume, not the tube type that runs vertical which I am familiar with. The pressure is about 32 lbs on a guage when it's hot then it pops off . So I assume the guage is good. Thanks for the info.

[Diceman]

Do this. Drain boiler down to about 12 psi. Shut off incoming water supply, make sure it is off tight, not any water leaking in, and fire it up. If it still builds rapidly and blows your tank is kaput and I think it was undersized from the get go.

[saccounty]

diceman I'm going out to do that right now.

[saccounty]

diceman I drained it down to 12psi, shut off the water, fired it up, and it did not build pressure rapidly so apparently it's not the tank and it was just overfilled. When I opened the fill valve no water went in (there is a water meter just for the boiler) but it is hot now and water expands when heated so the test will be tonight when the water is cold. Earlier when I drained and refilled it was cold. So thank you this leads me down another path.

[Diceman]

You are somehow letting too much water into it, the prv is is messed up, got something stuck in it or something like that, hard to tell from here.
Not sure what you mean about the test and water being cold tonight??

[skorch]

question? the expansion tank, did you quickly open it (ie: screw drive or such) to see if water comes out? think you are getting to technical now. need to go back to basics. re-check that expansion tank.

[kenb]

by any chance is there a tankless domestic hot water coil leaking in this unit?

[snipe70e]

I seen many PRV that will leak through even when new. If you are comfortable try this, shut off the make up supply when the boiler is hot and check the pressure before it fires up in the morning.

Most expansion tanks are not valved up right. You should have a valve to isolate the tank, and a valve to drain the the expansion tank, so you can test the tank.
Len

[Noel Murdough]

The key clues here, that are not being discussed....

He has a water boiler, with a gauge glass.

His tank is full by this glass.

He drained water out and checked for pressure how? He did it with system pressure NOT isolated.

What does this mean?

To me, it shows a lack of understanding of even the basics.

I think there is NO diaphragm tank.

I think it is a conventional expansion tank, with a gauge glass on it. I think it has no air in it. I think it has water in it at 12 PSI cold, because the GLASS IS FULL.

I think you could drain water from it all day at 12 PSI and it STILL would have no air in it.

What do you guys think?

Noel

[cynic]

Think you are right Noel.... wonder if that air vent has anything to do with it filling up.

[bobby7388]

Originally posted by Noel Murdough
The key clues here, that are not being discussed....

He has a water boiler, with a gauge glass.

His tank is full by this glass.

He drained water out and checked for pressure how? He did it with system pressure NOT isolated.


What does this mean?

To me, it shows a lack of understanding of even the basics.

I think there is NO diaphragm tank.

I think it is a conventional expansion tank, with a gauge glass on it. I think it has no air in it. I think it has water in it at 12 PSI cold, because the GLASS IS FULL.

I think you could drain water from it all day at 12 PSI and it STILL would have no air in it.

What do you guys think?

Noel


If that is the case then the tank can be charged for testing through the airtrol(not brand specific).
Keeping in mind that the water level needs to be taken down below the airtrol inner tube, or 1/2 gauge glass for good measure.