Hot Water Boiler System: Can't bleed air out of system

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Old 12-27-10, 02:24 PM
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Hot Water Boiler System: Can't bleed air out of system

Hello,

I've been reading posts by some of the experts on here and am posting because I have a problem w/ air in my 3 zoned hot water boiler system. Zone3 is upstairs and when only that zone on, the rushing water noise is very loud. If I have the other 2 zones (Kitchen & Living Room) on, the noise still exists but is less of an issue. I bought this home in May10.

I've had 2 pro's out to look at the system. One suggested an air scoop and the other bled/drained each of the zones including the expansion tank. The noise went away for about an hr then came back just as loud as before.

I have an air seperator setup, but no bleed value, it seems to just be tying in the water supply to the boiler. I have floorboard radiators throughout the house and bleed values only and a couple upstairs. I have tried bleeding those valves and I get mostly water w/ what I presume is air 'popping' sounds. It doesn't help. Do you think an air scoop is way to go?

Here are the details of my setup:
Dunkirk PVWB-5D
18-20psi
185 degrees
Circ Pump = B&G
Inline Air Seperator = Bell & Gossett 1AS- 1 1/4 (No bleed value, seems to be used incorrectly)

Thanks in advance for any feedback or help you can offer.

Mark
 
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Old 12-27-10, 02:43 PM
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Originally Posted by mrandy7 View Post
Hello,

I've had 2 pro's out to look at the system. One suggested an air scoop and the other bled/drained each of the zones including the expansion tank. The noise went away for about an hr then came back just as loud as before.

I have an air seperator setup, but no bleed value, it seems to just be tying in the water supply to the boiler. Do you think an air scoop is way to go?

Mark
Not a pro but got to know what kind of expansion tank you have? Is it solid or bladder?

If solid which makes sense there are no (auto) air bleeders in the system, just manual at the rads. Solid expansion tank uses the air space to convert oxygen to nitrogen I think, which is why there is little rust in iron connections. That is how it is suppose to work, but if there is a leak then fresh water will bring in more air, if there is an auto bleeder then the air cushion in the solid tank will be lost. (but not in an hour I think)
 
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Old 12-27-10, 02:50 PM
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I am not sure what the difference is between bladder and solid expansion tanks. Mine is mounted above the boiler on the ceiling of my basement and if fairly large.

Only some of the floorboard rads have bleeds. All are manual.
 
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Old 12-27-10, 03:21 PM
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That is solid, no bladder as the water expands it is cushioned by the air space against the water, no bladder separating them. Only bleed method is manual. (no auto air separator)

What is the pressure of your system?

When I bleed my 3 story building I had to bring the pressure up to 25 to get the top floor moving enough water to push the air out, continually topping up with fresh water to maintain that pressure as I bleed rads. When done brought pressure back to 18. (also had drained the expansion tank earlier for another issue)
 
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Old 12-27-10, 03:26 PM
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Originally Posted by mrandy7 View Post
...and the other bled/drained each of the zones including the expansion tank.
Please post photos of your system. http://forum.doityourself.com/electr...your-post.html

I'm very curious what your mean by the serviceman "bled/drained the expansion tank"? Make sure your photos include the expansion tank and everything that connects to it, including the air separator.

Has the noise been going on ever since you moved in, or did it start more recently?

Best to read and post the pressure and temps two ways - with the system hot and with the system cooled down to room temp or a least to about 100 deg.
 
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Old 12-27-10, 03:37 PM
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The serviceman basically drained each zone a few times and then drained the expansion tank as well. There is a value and a hookup for a hose on the expansion tank. Here are some photos of my setup:

11.30 - furnace 002 | Flickr - Photo Sharing!
11.30 - furnace 003 | Flickr - Photo Sharing!
11.30 - furnace 004 | Flickr - Photo Sharing!
11.30 - furnace 005 | Flickr - Photo Sharing!
11.30 - furnace 006 | Flickr - Photo Sharing!
11.30 - furnace 007 | Flickr - Photo Sharing!

Thanks for the help. Let me know if there are any other shots you need me to take.
 
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Old 12-27-10, 04:02 PM
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Draining the zones or the expansion tank would accomplish nothing unless air came out. I suspect you were had.

See the red air separator? The top connection should go to the bottom fitting of the expansion tank, with the piping sloped up all the way. Where it is makes no sense to me. Presently, the bottom of the expansion tank is piped up to the relief valve line - not much air to be separated there!

The pressure reducing valve should be piped directly to the boiler.

We still need pressure and temp readings, both hot and cold.

Before you call any other serviceman, check references and make sure they have extensive boiler experience! Somebody 50+ years old, named Clarence, Elmer, or equal. (Nobody named Kevin.)
 
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Old 12-27-10, 04:13 PM
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System pressure is between 18-20.
 
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Old 12-27-10, 04:18 PM
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Yes, I agree. Both servicemen that came out were basically guessing at the problem. I've learned more on this msg board than either of the previous trips.

Pressure is currently 18 and temp is 185. How long would I need to shut down the boiler for to get the resting/cold temp and pressure?
 
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Old 12-27-10, 04:23 PM
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Originally Posted by mrandy7 View Post
How long would I need to shut down the boiler for to get the resting/cold temp and pressure?
Go by the temperature gauge on the boiler.

But, if I'm correct, until the system is repiped, any fixes will be temporary. Others here may chime in, too.
 
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Old 12-27-10, 04:26 PM
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Originally Posted by Mike Speed 30 View Post
See the red air separator? The top connection should go to the bottom fitting of the expansion tank, with the piping sloped up all the way. Where it is makes no sense to me. Presently, the bottom of the expansion tank is piped up to the relief valve line - not much air to be separated there!
Mike my system is piped at the pressure relief valve going to the expansion tank too! I'm guessing 40 years ago they had a different thought process. But what mine does not do is have that sloped line, nor is there an air separator. From research lately question why one boiler had auto air bleeds and the other none. I found some clues to why not, and basically it is that the heat changes the air to a non oxygen gas within a couple of days that will not corrode iron fittings.

Correction it is not on the pressure release but the cold water fill were it belongs (sorry Mike)

So on a close system with no issues (leaks) why is there an air separator?
 

Last edited by grumpy_guy; 12-27-10 at 04:46 PM.
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Old 12-27-10, 04:29 PM
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Originally Posted by grumpy_guy View Post
So on a close system with no issues (leaks) why is there an air separator?
To continually remove air from the circulating water and put it back into the tank. Air continully gets into the circ water from either make-up water to the system or from air-laden water expelled from the tank during heat-ups.
 
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Old 12-27-10, 04:29 PM
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Since I bought the home in May, I haven't had to run the boiler until Oct/Nov and the noise has been present the entire time. Here is a list of what the previous homeowner had done as a requirement for my purchase of the home.
  • Cleaned Boiler
  • New 1 1/4 ball valve
  • Relief Value
  • Pressure Reducer Valve
 
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Old 12-27-10, 04:41 PM
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Since the seller replaced the pressure reducing valve as a condition of sale, I'm wondering if the strange piping arrangement might have occurred then?
 
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Old 12-27-10, 04:46 PM
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My home inspector put this in his report...
"Improper discharge pipe on TPR valve, this should be metal."

I believe that along w/ check of Carbon Monoxide were what was done prior to my purchase. I have a copy of the invoice and is was about $1,100 for the items in my previous post.

But yes, I suppose it's possible.

The note on the service invoice also says "repped expansion tank". Not sure if I'm reading that correctly though.
 
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Old 01-01-11, 09:29 AM
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I was finally able to get the 'resting' temp & pressure for my boiler.

Resting:
100 degrees
18 psi

Running:
185 degrees
18 psi

Based on what Mike says below it seems whoever did the setup of my system didn't know what they were doing. Can anyone confirm I have the correct fix documented? It sounds like the relief valve being hooked to the expansion tank is pointless since the expansion tank handles excess pressure. Instead, the air seperator needs to hook to the expansion tank w/ sloping up the entire time.

What would need to happen to the existing relief valve? Can that just sit off the boiler w/o a hookup anywhere else?

Thanks so much for all the great help and Happy New Year.
 
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Old 01-01-11, 10:29 AM
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Yes, the relief valve can be left as is, but the line presently going up to the exp tank should be plugged or capped. The relief valve needs to be connected directly to the boiler with no shutoff valve in between. You can put a normally-open shutoff valve between the air separator and the exp tank - that will make maintenance easier.

You'll be depressurizing and partially draining the boiler to correct the piping. While you do that, replace the boiler's pressure/temp gauge. Evidently, it is shot. The pressure should have increased in going from 100 deg to 185 deg. Get a Winters (or similar) tridicator with temp range up to 230 deg or so and a pressure range of at least 30 psi.

Good luck.
 
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Old 01-01-11, 12:33 PM
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invoice also says "repped expansion tank". Not sure if I'm reading that correctly though.
How about REPIPED ? it seems pretty clear to me that the expansion tank was probably connected to the IAS originally. Why it was moved to it's present location is anyone's guess.

There is nothing wrong with the water feed line tee'ing into the line from the IAS to the expansion tank.

The up slope to the tank does not need to be that extreme. An inch per foot is more than enough. The piping to the tank should be 3/4" pipe.

Looking at the pics, the hot supply coming out of the boiler heads back toward the wall, then to the left, then up, then to the right and the IAS, further to the right and then up again... that's really whack... and it appears that whole run of piping is 'sagging' too. The weight of all that pipe filled with water shouldn't be supported by the boiler or itself... there should be a support strap going up to structure from the area of the elbow to the left of the IAS. In fact, it should probably be LIFTED a little bit.

When the connection to water supply line is removed to change the tank piping would be the time to add that support strap, and lift that pipe a bit... in other words, 'preload' the support strap a tad...

Yeah, capping or plugging the current pipe to the expansion tank would be acceptable, but I would probably remove that Rube Goldberg setup and put the relief valve directly onto the nipple out of the boiler. Although, it could be helpful in the future to have a 'purge valve' at that point... in which case, leave as is, and thread a boiler drain into the top of the tee in place of the pipe to the tank.

OH... almost forgot... did I hear Mike paraphrasing my Mantra?

NEVER TRUST A BOILER GAUGE! I have no doubt that part of your problem stems from the fact that your gauge is toast. If it doesn't move off 18, that's a really good clue right there.

If that gauge was trusted by your repair guy, he was chasing his tail. You might not even have 10 PSI in the boiler... and that would certainly account for air noises...
 
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Old 01-01-11, 12:51 PM
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Thanks for the info guys! I really appreciate it. Do any of you know any quality boiler guys in Chicagoland you could recommend? Is there a way for you to ballpark and estimate for me? I'm guessing anything that involves moving pipes will run close to 1K.

Happy New Year
 
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Old 01-01-11, 12:53 PM
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Why on earth would there appear to be a dielectric union used to connect the expansion tank to the system?

By the way, the plugged connection at the bottom of the IAS would be an acceptable place to pipe in the make up water as well.
 
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Old 01-01-11, 01:36 PM
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It looks to me like a half-day job for one plumber. You can guess their hourly rate better than us. Plus maybe a couple of hundred for material. He'll need to come first to plan the job and identify the necessary material, including a replacement temp/pressure gauge. If everything seems stabilized, as least temporarily, maybe you can wait until spring and do the work yourself when you're not under the gun, winter-wise? Probably now that you've got the exp tank filled with air, it could be OK until spring - but avoid tempting fate my monkeying around by chasing noises, etc., unless necessary.

To find somebody to do the work, check with others that have hot-water boilers. From the looks of your photos, you must live in a somewhat older neighborhood - where most everybody has the same type of heat. Or watch for a plumber's truck coming or going to your neighborhood, and interview him on the spot. Any 2-flat or 4-flat in Chicago likely has hot-water heat - and there will be plumbers showing up periodically. This job should be well within the capability of a one-man show - the big companies might not be too interested. Be prepared to fend off sales pitches for a whole new boiler.

As Trooper said, use nothing smaller that 3/4" pipe from the air separator to the exp tank. (Not sure, but that rogue pipe that needs to come out may be only 1/2".) And yeah, just remove that union and the rogue pipe, and thread in a valve or plug into the tee in its place. Such a valve could serve as a purge valve, but the manual lever on the relief valve can accomplish the same function.

Re: the dielectric union. Totally not necessary, but maybe the Rube that put it in thought he needed a union someplace in that line, and only had a dielectric type with him. Since the line is soldered copper, no union was necessary at all.
 

Last edited by Mike Speed 30; 01-01-11 at 03:23 PM.
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Old 01-01-11, 03:29 PM
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Looks like another DE union at the reducing valve up top...
 
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Old 01-01-11, 04:45 PM
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Originally Posted by NJ Trooper View Post
Looks like another DE union at the reducing valve up top...
Hmm. Yeah, just after the auto fill valve. Hard to understand the thinking.
 
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Old 01-02-11, 07:56 AM
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Another theory about the dielectric unions. Perhaps the person who did the work was an apprentice plumber who had replaced gas-fired water heaters. Since those heaters typically have a sacrificial anode rod, dielectric unions are regularly used, presumably to localize the cathodic protection to the water heater itself. (I don't know how effective the dielectric unions are for that: the water heater tank is still electrically connected to the gas piping - which winds up being connected to the plumbing system, one way or another.

Maybe the theory is that with iron higher (by about 0.5V) on the electromotive series than copper, dielectric unions are called for at any steel-to-copper connections to prevent galvanic corrosion? Under that theory, one could need several dozens of dielectric unions throughout a home's plumbing or heating system. Obviously, that is not standard practice and doesn't seem to be necessary.

P.S. Another source of recommendations for plumbers, etc., is to go to a good, locally owned hardware store and ask them for a couple of names.
 
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Old 02-03-11, 09:29 PM
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With the type tank you are working with, you should have the tank about half full of water,
shut stop valve pump 12 lbs. of air into the top part of the tank. Out the top of your air separator you should have a auto bleeder. charge your system, get the air out of system.
and then when you have the system up to your 12 lbs cold pressure, open the tank value. This tank is not there to bleed air into. It is there so when water is heated , it can expand into the tank and pressure will go up some. When the water cools off the water will leave the tank some and the tank will go back down to the same water line.
The feed value should go in the return line between the boiler and the first stop valve.
Paul
 
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