Banging coming from boiler ....

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tombstone

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Good Morning!

I had a new Bryant boiler installed in my home about nine years ago. They didn't install an air removal device and used the old espansion tank (non-bladder). I have a two story cape-cod.

I recent had to resolder a connection to a radiator, replace a few bleeder screws and remove a radiator due to a remodel project. At the same time my boiler began to bang whem the burner warms up. When the boiler turns off and just the circulation pump is running all is well.

I've had 2 different companies come over to take a look. The first suggested that I replace the pump, a Taco 007 F5, which I did. The second suggested that the pressure in the system was too high and backed it down to about 17 psi. Well, the noises are still here.

My neighbor, a master plumber, suggested that we install a air removal device and replace the old expansion tank with a newer model with a bladder.

Can anybody else offer any advice? I hate to keep paying people to come over and take a shot at it.

I'm assuming its air in the system as it didn't do this at all before.

Also, some of my radiator bleeders don't allow the water to shoot out, it just drips. Could that be a source of my issue as well?

THanks for any and all advice to rid myself of this problem.

Jeff
 

Jadnashua

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Air extraction device and a bladder tank will help keep the pressures even and keep air out. Does your system have a reliable pressure gauge? When it is making noises, what is the pressure at that point? To keep from getting cavitation or boiling in the heat exchanger, you need to maintain a good flow with no air and maintain the proper pressure. Too low, and it boils, steam can ruin a boiler designed for hot water. A bubble going through could (it would have to be big) allow the heat exchanger to get hotter and let the next water flash.

What temperature is the boiler running at? Most modern ones don't run above around 180-190 (maybe a little warmer - depends). How hot is yours?
 

tombstone

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The temp. of the boiler is 180 degrees and the pressure seems to run at 20 psi during quiet times and when the boiler is banging/popping.

On the suggestion of the first technician who thought the flow was the problem, I did replace the pump about two weeks ago.

As I mentioned the system has been brought down, opened, closed and brought back up several times during the past few months.

If I'm not getting a nice stream of water out of a bleeder would that suggest that the bleeder is clogged and not letting the air out?

Thanks again! I certainly appreciate the assistance in trying to troubleshoot this.

Jeff
 

Jadnashua

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Do you get anything out of the bleeder? If you're getting air and water spitted out, keep it open until you get only water. If you don't have an auto-feed to replace water volume as needed, this would reduce the system pressure and the boiler may (should, depending on how low it goes) turn off. Air inside a hot water boiler is not your friend. Too much air can cause an air lock and prevent the pump from circulating water. This can cause the water in the boiler to flash to steam, messing things up. You need to get all of the air out and keep it out. I think a bladder type expansion tank and a good air scoop or extraction device would be my first venture. An expansion tank with an air/water interface would seem to just allow air to continually be absorbed and mess up the volume of the expansion available. I'd get rid of that variable with a bladder tank.

Sometimes, it is just easier to shut the boiler down, and have someone watch the pressure gauge, opening and closing the fill valve to keep the pressure say less than around 20# or so, and just go around and open bleeder valves until they all run with no air. The air will migrate to the highest point, but since some will be disolved in the water, it can take awhile to get it all out. Once you get all of the air out, the pump can move the water as designed. A 007, depending on the head pressure may not be able to pump through a large volume of air (air locked)- you have to fill the pipe with water first by purging it well.
 

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I have two bleeders that water just drips out of when opened. There is no air or at least not the hissing of air rushing out that I'm used to. I'm wondering if these two are prohibiting me from getting the remainder of the air out?

I do have an auto feed valve.

I am planning on having my neighbor install the tank and a taco vortech air seperator this week-end.

I have new bleeders I just haven't installed them yet. If I turn of the boiler and shut the valves leading to and from it along with the expansion tank valve will I be able to remove the old and install the new? In the past I've had to bring the boiler down in order to do so.

I just took a look at things again the the gate valve for the old expansion tank has a lot of corrosion on it - obviously indicating a small, albeit present leak. I was able to tighten up the packing nut a bit more and things seem to be good as far as the valve is concerned.

The banging persists but the radiators are making good heat.



Thanks again!
 
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Jadnashua

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Much prefer ball valves. If the boiler is off, and you can isolate the expansion tank with a valve, then yes, you can just remove the old one and replace with a new one. Double-check the pressure before you install it. They're normally set for around 14#, but if you run your system higher, it wouldn't hurt to bump it up a little. If the tank's pressure is close, but less than the normal pressure, it won't be flexing as much and can last a little longer while still doing its job.
 

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I took another look at the system pressure - it was at 20 psi. If I remember correctly, the rule of thumb is 7 psi per floor so I bled off the expansion tank and brought it down to 15 psi. I also backed off the autofill.

I was poking around in the joists in the basement and found two spots where the copper it corroded and one of them is dripping. I'm assuming that this, along with the valve, is a MAJOR contributor to my problem. The copper pipe used to plumb in the rads is 1/2 OD and it looks like the main pipes are 1". Would a plumbing supply house be able to supply those items?

Also, with March just around the corner, could I let this go and repair it off season? I have another tech scheduled to come over on Thursday, but I don't know what he'll be able to do that the other two weren't.

The other area of concern is the two bleeders on the rads that just let the water drip, as opposed to stream, out. I need to bring the boiler down to replace those and might as well replace them all.
 
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Krow

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2 things you could look at

1)Check to see at what temperature the water gets to when the pump kicks in . If its running all the time , Disregard this statement.

If it kicks in at 120degrees or higher, lower the limit to 115 or 110 degrees and see if that helps.

2) Is it possibble that the piping in your system is getting hot or warming up very quickly, therefore creating the pipe expanding noise. Lowering the pump limit could help in this case as well.
 

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The sounds I'm hearing are coming from within the boiler and not the pipes themself. If I press my ear against the boiler I can hear the "popping" coming from within.

Are the limits set in the aquastat?

I sleep horribly as it is and this is just compounding the issue.

Hopefuly I can make some headway.
 

Krow

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.

Are the limits set in the aquastat?
.
Yes

If this boiler is fairly new, there should be 2 limits (usually grey boxes)

The high limit is set anywhere between 180-200. When the water temp gets that high, this will stop the boiler to give it a chance to cool down (DO NOT ALTER THIS SETTING unless you have done it before)

The aquastat controls the pump. It will come on that the setting temperature from the stat. The idea is to get the water flowing out of the boiler before it has a chance to start banging (boiling). The water boiling would create banging
 

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If there is a leak in the system where it needs to frequently add water, and the water is hard, you will be adding calcium/lime etc. and could eventually coat the heat exchanger, insulating it somewhat. This could also be the cause. If the system is not leaking, the amount of minerals in the fill isn't that much, and this is unlikely to happen. There may be a de-liming procedure that could be done, but I'd make sure there aren't any leaks, the pressure and air issues are addressed first. The inspection procedure and cleaning might be a big pain, and may not be needed. See what the pros have to say...

You must be moving the water through the boiler while the burner is on, and an air lock could prevent that from happening.
 
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