All of a suddne 40 PSI in a OLD hot water/radiator Boiler System?


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Old 04-12-14, 10:50 PM
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All of a suddne 40 PSI in a OLD hot water/radiator Boiler System?

Hello DoItYourselfForym!

Looking for a little insight here.

I recently purchased a home built in 1919, complete with a heating system of roughly the same age.

The gravity fed system is comprised of an old hot water boiler (natural Gas, probably converted from Coal), Five old style radiators, one hot water fin style baseboard radiator, and an old expansion tank (up near the attic)

I'll do my best to describe the system. I unfortunately have no way to take photos right now. The boiler is gas fired, has a pressure and altitude gauge, and a temp gauge. On the right side is the cold water fill, at the bottom. On the top is a pressure release, and the hot water send and return.

The expansion tank sits up near the attic, has a feed and return, coming into the bottom and side near the bottom. At the top of it is an overflow I assume, that leads to the roof. There is also a bleed spigot.

The radiators are the old style, cast iron I assume, with a bleed valve at the top, with water entering and exiting wither side of the radiator, on the bottom.

There is a hydrostat set to 170.

Aside from the valves on the radiators themselves, there are no shutoff valves anywhere in the system

When we bought the house a few months ago, all the radiators seems to work just fine.

During the process of a remodel, we replaced one hot water baseboard radiator, and I assume got air into the system, because that radiator never got hot.

So in an attempt to bleed the system (admidiatelly, I was not sure what I was doing), I hooked a hose up to the overflow, ran it to a drain, and used the fill valve to cycle water through the system, hopefully pushing the air bubble through. That did not work. Water did, however, drain from the roof, from the expansion tank.

Then I bought a radiator key, and did it the correct way, after some research.

Sometime between now and then, the water pressure has gone from 15 PSI or so, to 40 PSI, and now water leaks from one of the radiator valves (not the bleed).

I figured water had filled the expansion tank, so I drained that, and got a few gallons out. The pressure gauge still read 40. So I figured I would drain the system and start over. Then repressurize.

I drained what Seemed like 40 gallons or more of water from the system, via the overflow valve, and the other spigot on the fill side of the boiler.

I know at least some of the radiators had emptied, because I could gear water gurgling through them, and they sounded hollow.

I opened some bleed valves to releave whatever pressure there was, and air pushed out. I left all of them open for a while.

The strange thing is the pressure reading on the boiler gauge never really changed. Went to about 35 PSI. But not below.

I do not understand where this pressure reading is coming from. I guessed there must still be some air blockage somewhere, so I tried to refill and bleed at the radiators.

I opened all the radiator bleed valves, and turned on the fill. Air began pushing out the bleed valves, and one at a time, water, so as water began squirting out, of course I closed the bleed valves.

Boiler pressure was 50 PSI at this point. I figured there still must be an air bubble, so I fired up the boiler in the hopes to move it out. Pressure stayed about 50 PSI, temp went from 80 degrees to 140.

So what could be going on here all of a sudden to jack the pressure from the normal 10-15 PSI it was running at before, to the now overly high 40 PSI? And more importantly, what can I do to get it back to normal pressure.

Sorry for the overly long post, and thanks in advance for any help.
 
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Old 04-13-14, 02:56 AM
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Shut the boiler off and call someone!
 
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Old 04-13-14, 05:29 AM
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It would appear you have a defective pressure gauge.
 
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Old 04-13-14, 08:42 AM
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Read this:

http://www.doityourself.com/forum/bo...ure-gauge.html

If this is still a gravity system, it means that it is not a 'closed' system. That vent to the roof is the overflow at the top of the system. If this is true (and it may not be!) it's where your 'altitude' gauge comes into play. You need to have a good idea of the HEIGHT of the system in order to fill it to the proper pressure (feet).

It's 0.432 PSI per FOOT of height that you are looking to set. If it's say 35 feet from the gauge to the expansion tank, then you need to set the ALTITUDE to that, which corresponds to appx 15 PSI.

If you really had 40-50 PSI in the system, water would be gushing out that overflow... if it's not plugged.

I agree with Tom, you need a new gauge to start with and then go from there.
 
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Old 04-13-14, 09:11 AM
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Thanks for the reply.

I don't believe the gauge is defective, because it was reading 10 PSI, and the radiator valves were not leaking, now it reads 40-50 and they are.

As far as "calling someone", I wish it was that easy. So far everyone I have called dosent want to work on it because its 100 years old, and they just want to sell me a new boiler. It was, and still is working fine, aside from the high pressure.
 
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Old 04-13-14, 09:16 AM
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Hi NJ Tom,
Thanks, I posted before I saw your post.

I'll verify the gauge. Can I take the test reading off an open overflow?

I did see water coming off the roof at one point, so I know the overflow is there. I guess it could have become clogged. I'll see if that can be checked.

It's so mysterious, in that it read 15 PSI, and all of a sudden it is reading 40 now. I guess a clog would explain that.
 
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Old 04-13-14, 09:49 AM
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Can I take the test reading off an open overflow?
When you say 'overflow', I'm not sure what you mean? You talking about 'pressure relief' ?

You need to measure the pressure at the boiler, not up top, if that's what you mean.

There must be a hose spigot drain on/near the boiler? That's where you would install the test gauge.

It's so mysterious, in that it read 15 PSI, and all of a sudden it is reading 40 now. I guess a clog would explain that.
It's pretty clear that after 100 years or so, that gauge has given up it's ghost. Happenz... stuff breaks... usually takes less than 100 years though!

It does seem that the system is an 'open' one if you have a drain to the roof, and that makes it physically impossible for the pressure to be any greater than 0.432 X HEIGHT. That's physics, and those laws can't be broken, but your gauge can! The only way you can have 40 or 50 PSI in the system is if the system is about 100' tall! This is not a 10 story home, right?
 
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Old 04-13-14, 10:30 AM
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Hi Tom.
Yes, I meant pressure relief.

So my question is can I measure the pressure with the test gauge on the pressure relief side of the boiler? Put the gauge on the pressure relief tube, and manually open the pressure relief valve.

This is a 1 story home, Boiler is in the basement. So I'd guess the elevation difference between the boiler and the expansion tank is 15' or so.

The house sits at 5,280 ft above sea level if that makes any difference.
 
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Old 04-13-14, 10:42 AM
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Hi Jay, I'm not Tom... call me NJ...

Sure, if you can securely attach it somehow and you don't have a hose bib drain on the boiler... isn't there one?

If the system is in fact 'open gravity', and there's 15' between the boiler and the roof drain, then you can't possibly have a pressure any higher than about 7 PSI.

Yes, the altitude above sea level does make a difference, but only a slight one. The 0.432 figure is valid only at sea level where 14.7 PSI is the 'normal' air pressure... and I'm a 'flatlander' so without googling I can tell you what 'normal' barometer is at 5K+ altitude. Let's suffice to say that it will be a little less, and so will the 0.432 PSI per foot number I quoted.
 
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Old 04-13-14, 11:03 AM
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Hi NJ,
Thanks, Sorry about that. Not sure where I got "Tom" from. Not enough Coffee this AM.

Yes, there is a hose bib on the right side of the boiler. It is connected to the pipes that lead back from the radiators, so I imagine it will be reading pressure of the whole system, not just the boiler itself, but since it is all interconnected, I guess that is OK.

I'll see what I can come up with and post back when I have some figures.

What would be the best way to see if the overflow at the expansion tank is clogged?

The reason I am wondering if it somehow got clogged is if I leave the fill valve to the boiler open, the gauge on the boiler (which could be broken) goes to 60+ PSI, but water is no longer coming out the overflow outside.
 
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Old 04-13-14, 11:32 AM
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The reason I am wondering if it somehow got clogged is if I leave the fill valve to the boiler open, the gauge on the boiler (which could be broken) goes to 60+ PSI, but water is no longer coming out the overflow outside.
We don't yet know for sure if you do in fact have what's called an 'open' system.

How does the pipe to the roof connect to the expansion tank? Is there any kind of a pressure relief valve between that pipe and the system?

Too bad you can't take pictures!
 
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Old 04-15-14, 11:45 PM
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Is it possible that instead of having an open pipe at the top of the system you instead have a pressure relief valve in the attic, with its discharge port going to the exterior? What is the PSI of your potable water supply? How do you fill the system? Are you going through a pressure reducing valve (PRV) and a backflow assembly like you should? If this old system has no PRV you could be putting potable supply pressure into the heating system. Even with the fill valve in the closed position it could be leaking pressure forward if the valve is defective, or you cold have a defective PRV. In either case you would ALSO need to have a plugged relief port or a defective/inoperative pressure relief valve that is not opening as it should at 30 psi. Seems like a perfect storm of conditions but long shots do happen, which is why everyone says that your gauge is wrong as this would be a much more likely scenario. Is your boiler system being used to heat potable water, with an indirect storage tank? A failed heat exchanger would also allow potable pressure to leak to the heating side.
 
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Old 04-23-14, 02:59 PM
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Update-Bad Gauge

Hi Fellas,
I just wanted to give an update and thank everyone for their input.

I went to the plumbing supply house, and picked up a 0-30 PSI gauge, hose bib adapter, and some valve packing.

As you expected, the gauge was bad (read 40 PSI disconnected). I replaced it with the 0-30 PSI one, and the boiler pressure reads 5-6 PSI cold. I rebuilt the radiator valve with new stem packing, and it stopped leaking. Bled the radiators, and we should be good to go once winter rolls around again.

Thanks again for the help. I neglected to take any pics, but next time I'm down there i'll try to take a few for those interested.
 
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Old 04-23-14, 03:24 PM
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Yeah, I knew that gauge was toast...

but we should be sure you really have a gravity system before saying 'fixed'.

Your system has NO CIRCULATING PUMPS attached, is that correct?

How are you filling the boiler now with the gauge issue resolved? Just open the valve until water runs out the roof vent?
 
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Old 04-23-14, 03:53 PM
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Yes, its Gravity Fed.
There are no recerc pumps, etc, and the boiler guy who inspected it, but didn't want to work on it, did say it was an old gravity fed system.

The boiler fill has a valve that comes in from the cold water house supply. I turned the fill on, and began to bleed the radiators. The gauge went to 30, and the Blow off valve on the other side of the boiler opened.

I turned the fill off, and the system seems to equalize at 5-6 PSI.

If I open the fill valve slowly, the gauge reads 10-15PSI, but once you close the fill valve, the system equalizes itself to 5-6 PSI.
 
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Old 04-23-14, 04:01 PM
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When the system 'equalizes' itself at 5-6 PSI, is there water coming from the roof vent?

Just wondering where that pressure is going... and why it's not venting fast enough to keep the relief valve from opening.
 
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Old 04-23-14, 04:16 PM
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I didn't have a chance to look at the roof vent, but my guess is there is some air still in the system and its compressing. I was going to run the boiler for a while to get the water moving next time im down, so the air will make its way to the top of the radiators.

I quickly bled the radiators, but didn't really run the bleeds as long as I think I should have, I was running out of time.

I'll post back in a few weeks.
 
 

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