Loud bangs in boiler pipes, major flucutations in pressure


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Old 12-06-09, 10:37 PM
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Loud bangs in boiler pipes, major flucutations in pressure

I have an old Weil-McLain floor model boiler I'm not sure of the model but if it helps it's about 30-40 years old, it 31" tall and is gray/blue in color; is natural gas fired. It also runs 3 zones with copper tube/aluminum fin baseboard radiators. My zones are basement, 1st floor, and 2nd floor. My home is a 2 story wood frame house about 50+ years old.

Last year my pump gave me some trouble but got through the season. My zone valves also took some maintenance. They were old Dole HM2-3/4 zone valves

I just finished replacing the circulation pump. The pump was the recommended replacement according to Grundfos. The old pump was a 15-42F and the new one is a 15-58FC. I also installed 3 new Taco E075C2-3 zone valves. I also installed a new Honeywell Fv180 air vent. This air vent sits directly on top of the boiler. I also installed a new pressure temp gauge which is on the side next to the pressure relief valve.

After I completed installing the new parts I first bleed the system with the zone valves open but without the pump running. I then bleed it with the pump running. I have also now bleed the system hot. For clarification By bleeding I mean that I have gone to each zone and opened the bleed valves until no air was evident. Some time this meant many bucketfuls of water. I also opened the cap on the new bleed valve on top of the boiler.

My problem now its that the pipes near the boiler bang (like a hammer hitting them) and my pressure wildly fluctuates 5-20 PSI. My pressure will also build from 10(AVG) up to as much as 30 then my relief valve pops.

After the burners go off the air valve will then hiss like a pressure cooker for about 1 minute.

I initially had my accumulator tank set at 17 PSI but I was getting regular relief valve pop offs. i then lowered it to 10 and it helped. This has been going on for 4 days.

What am I missing here?
 
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Old 12-07-09, 01:57 AM
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I hope that you also replaced the safety valve on that beast of a boiler. It sounds like you still have air in the system.

I'd like to see some pictures of the boiler and piping. To post pictures you need to first upload the pictures to a photo hosting site such as photobucket.com or villagephotos.com. and then post the public URLs for the pictures (or album) here. More pictures are always better than fewer. Please have CLEAR pictures and have both close up pictures and ones from a far enough distance that we can see how the various parts are interconnected.
 
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Old 12-07-09, 08:30 AM
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While we wait for pictures, tell us what type of expansion tank is installed: a conventional steel tank hanging from the basement ceiling or a bladder-type tank (looks like R2D2)?

If it's a conventional tank, a separate air elimination device should not be installed.

With your wild pressure variation, I'm suspecting a water-logged expansion tank.
 
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Old 12-07-09, 10:18 AM
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Pictures posted

Pictures by komputatek - Photobucket

I did replace the relief valve last year and so far it stays dry after it pops (no weeping)

As you can see the expansion tank is a bladder type. I had read some of the other posts and was wondering if it might be part of the problem.

Thanks!
 
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Old 12-07-09, 10:30 AM
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I believe your expansion tank is waterlogged. You can depressurize the water side, and pump up the air side to 12 psi through the schraeder valve.

But if the bladder is leaking, that won't help for long. As old and decrepit as the tank looks, I would replace it.
 
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Old 12-07-09, 04:56 PM
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circ

Is the circ pump in backwards?
 
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Old 12-07-09, 05:18 PM
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While the tank may in fact be pooched, I doubt that's what's making the gremlins inside the boiler get out their hammers. Sounds more like there's not enough water in the system.

Or as Bilbo says, maybe the pump is backwards... or possible cavitating...

On the expansion tank... that appears to be a FILL-TROL tank and valve. You can't just replace that with a standard tank.

See FILL-TROL in this brochure:

Amtrol Extrol / Fill-Trol brochure
 
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Old 12-08-09, 11:51 AM
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Fixed!

Thanks to everyone. but special "kudos' to Bilbo. My pump was in upside down!.

The new pump looks nearly identical to the old one so I assumed (you know what happens when you assume?) it was the same direction of flow. I turned it over,drained about a cup of water out of the Fill-Trol tank, then set it's pressure; bled it out, and now it's working better than I ever known it to.

Thanks again. Now I enjoy a quiet, smooth running system.
 
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Old 12-08-09, 03:17 PM
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drained about a cup of water out of the Fill-Trol tank,
How did you drain the water out of that tank?

Bilbo, good catch!
 
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Old 12-08-09, 03:27 PM
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Drined out about a cup of water

I guess I really didn't get much if any from the tank, but rather about a cups worth spilled out when I removed the tank so this could have been just in the line or control head of the tank. I did shake the tank and heard no sloshing.

Just a question to this though. I have my system pressure set to 17 psi but when it heats up it goes to 27-28. Is this Ok or does this Fill-trol need replaced? or is there still another problem? The relief valve hasn't popped once.
 
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Old 12-08-09, 04:56 PM
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Bilbo Is the circ pump in backwards?
Hey!! This sounds rather familiar! I had the exact same problem. As for the pressures, from what I have learned on here, is that from cold system pressure, hot system pressure will be 5-8 psi higher, and anything over 25 is not exactly desired. But maybe it could vary in this application.
 
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Old 12-08-09, 05:44 PM
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Originally Posted by komputatek View Post
I guess I really didn't get much if any from the tank, but rather about a cups worth spilled out when I removed the tank so this could have been just in the line or control head of the tank. I did shake the tank and heard no sloshing.

Just a question to this though. I have my system pressure set to 17 psi but when it heats up it goes to 27-28. Is this Ok or does this Fill-trol need replaced? or is there still another problem? The relief valve hasn't popped once.
Oh... you removed the tank from the system? and then set the pressure in the tank to 12 PSI with an accurate tire pressure gauge and re-installed?

You said the gauge is new?

You probably don't need 17 PSI when the system is cold. 27-28 is getting VERY close to the relief valve pressure... too high. I would not expect 10 PSI swing from cold to hot on your system.

How did you 'set the system pressure to 17' ?
 
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Old 12-09-09, 06:34 AM
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System pressure

I did initially set the tank pressure to 12psi with a tire gauge, but I then raised the pressure on the boiler gauge (by adding air to the tank) once the system was charged with water and purged of air. The boiler gauge showed 10psi when I had the 12psi charge in the tank.

The side of my boiler has an old hand written note on it showing 17psi. I was told several years ago that this pressure was right for the height of my house. My house is vary tall. This boiler is in my basement so from basement floor to the 2nd story floor baseboards it is about 22 ft. It takes a 40ft ladder to get on my roof.

If there is still a problem, I'm open to fixing it, but so far it's been great.
 
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Old 12-09-09, 03:02 PM
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raised the pressure on the boiler gauge (by adding air to the tank)
So after looking at the brochure, you definitely identified your tank / valve as a Fill-Trol... that's what I was after, and wondered.

22 feet from boiler to tip-top radiator shouldn't require more than 14 PSI. Given that it seems that your expansion tank is on the marginally small size (evidence the 10 PSI swing cold to hot), that 3 PSI might could 'make or break' whether the relief valve dribbles or not.

What seems strange to me is the you have that much pressure swing. With fin-tube baseboard throughout, there really isn't that much water in the system. The tank size you have should be large enough to limit the swing to maybe 5 PSI or so. I would think your tank was beat if you didn't say that you removed it and didn't feel any water sloshing inside. strange...
 
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Old 12-10-09, 07:38 AM
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you definitely identified your tank / valve as a Fill-Trol...

I did look it up on the internet and there is also a label on the tank identifying it as such.

Is there a possibility that the Fill-trol valve - the one the tank screws to is bad? What does it do? Should I replace the whole Fil-trol assembly? If I replace it would you recommend a direct replacement or convert it to a standard tank?
 
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Old 12-10-09, 02:57 PM
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The Fill-Trol is actually a pretty neat idea... I think there's a cut-away diagram that shows the 'plunger' that is installed in the expansion tank. What happens is that if the system pressure drops for any reason, the membrane in the tank will move up and push the plunger out, which in turn opens the valve a smidge, and feeds some water in. So, your system pressure will always (theroetically) match the air charge in the tank, which is the way it is supposed to be. There's no guessing if the air charge in the tank is low with this system, because you will also have low pressure in the boiler... the system pressure will more or less 'track' the pressure in the tank.

BUT, what it also means is that you MUST use the Fill-Trol type tank as a replacement, and you won't find them at HD or Lowe's. It also means that you will pay more for the replacement tank, IF you can even find one locally.

It sounds as though the system is working, and as long as the pressure relief valve isn't opening, you should be OK... but I would consider dropping a few PSI ... back to say 14, just to give you those few extra PSI of 'headroom'.

There is also a possibility that your existing boiler pressure gauge is not accurate. I hate gauges! Ya think ya can trust them, that they are your friend, and they turn around and stab ya in the back!

If you were to do some rework, I would recommend replacing with an off the shelf backflow preventer, pressure reducing valve, and standard tank. But it ain't exactly broke, so don't reinstall the operating system just yet! Might just be a missing dll file. Wait... I'm gettin' confused!
 
 

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