Harmonic Combustion Noise

ced48

Anybody had any luck getting rid of harmonic combustion whine? I have a Lochinvar WH55 that whines a little a 23, 29, and 38 percent fire. I have adjusted the pressure differential to factory specs, and the fan has been replaced. These steps both helped, but these 3 levels persist. Wish I could just bypass them like some of the commercial boilers can do. Unit is running on LP-

Tim McElwain

How much pipe on a horizontal run to the unit do you have? It is a good idea to have about 10 feet of at least 3/4" pipe on the horizontal to the unit. How close to the second stage regulator are you? Again at least 10 feet or more from the regulator.

ced48

Tim-I have about 20 feet of 3/4" pipe run on the horizontal-I only have one regulator, which the propane supplier assured me would be fine, small unit, Problem?

Tim McElwain

That should be fine, what kind of combustion readings did you get? Sometimes you can adjust with a little less O2 and CO2 up and whine will go away. Just watch your CO reading while doing this and stay within factory specs.

Ironman

I've had this problem with a lot, if not every WHN that I've installed. Adjusting the throttle screw to the higher or highest CO2 allowed in the specs solved it on all of them. Most, if not all were on LP.

ced48

I adjusted the throttle screw right up to 11 percent, and even a bit higher, without any success. It was then that I attacked the pressure differential adjustment. I was lean, and I adjusted it so it wavers in bounds of the factory specs, max of 11 percent CO2, min of 10 percent. Going higher on CO2 did not stop the problem, had to try. My thoughts are that a lot of these boilers might have the same problem, but are mostly run in the higher end of fire. I bought the smallest fire tube boiler out there, and new I was 50 percent oversized, but with the 5-1 turndown, I thought I could squeak by without short cycling issues. I was more or less totally successful, except for this low fire issue. Too bad, because you can walk right up to her closet, and have to check to see if she is on at most of the lower firing rates. I'll keep plugging away-

Zman

You didn't mention what your co is doing. It is important to keep an eye on it as you approach you high co2 /low 02 threshold.
I would not rule out the gas regulator completely. You might try adjusting the pressure slightly or replacing the regulator as a last resort.

BobC

This may not be applicable.

I have an EZ-Gas on a Smith G8-3, I have had a bad ow frequency rumble since it was installed a couple of years ago. The installer had no clue and neither did the guy who serviced it early this fall.

On a hunch I checked the input gas pressure on it and found it was dropping from over 8" to about 5" when it fired, the output of the valve regulator was bouncing all over the place.

I called the gas company and they verifies there was a problem with the service. The installed A new pipe from the street and a new meter. Now the pressure barely moves when the boiler fires and the output is steady.

I still have a little roar but it's been reduced by 80%. Your problem seems to be at low fire but I would made sure there isn't any flutter on the output of your boilers gas valve. If there is any, look deeper.

Bob

icesailor

For many soot suckers, the first thing some of us do is get out the high pressure gauge and check the pressure.

The gas providers are not your friends and buddies. Sometimes, they have more excuses than the guilty looking child standing next to the empty box of cookies.

ced48

It has ben suggested to me that this could be an issue with concentric venting, and or piping lengths of the venting, intake, system. I hate to tear this all out, redo, and have the same issue. Would just disconnecting the air intake test whether or not this is the problem? I have read of drilling a 1/4"hole in the elbow, but for different sounds, they don't sound like harmonic whines, more like fog horns and howls. Would reducing the exhaust outlet opening do the same thing as lengthening the run?

Tinman

See Ironman's post above. Hard to argue with that success rate.

ced48

Agreed, but it didn't work for me-I have had the boiler adjusted at the high end of CO2, and then some, no change to the whines, just makes all the other levels a bit rougher-

john p_2

Would love to see a pic of the system - mainly exhaust & intake piping and the gas piping at the boiler.

Tom_133

I have found it successful at times to get on with customer service, last time the guy had me take a pic of the system and send it to his cell. I was having a different problem but those guys are pretty good on their equipment. Just a thought if you are still dealing with this noise

Zman

If you cannot make the sound change or go away with tuning, I would think the noise is not the usual one.
You could experiment with partially blocking the vent (just while you are troubleshooting of course) and see what changes. Much easier than re piping.
My money is on the propane regulator on the outside of the building. I know it is hard to get your head around it but it can cause that same noise. I have seen and heard it myself.
Carl

ced48

Carl-I am going to try the blocking approach this weekend. I think I'll just slip a 2" x 1 1/2" reducing coupling, with a short piece of pipe, over the exhaust. I pulled the small plastic pipe off of the intake elbow, opening a small hole which allowed room air in, with no sound difference. The fact that all the noise is in the lower end of the firing range, seems to point to to much air flow, if adjusting the fuel mixture does nothing.

As far as the regulator goes, The pressure is a 11 W.C., and more or less constant at all firing levels. Could it still be the problem? I wonder wether the propane company will just swap it out, or tell me it's working fine, 11 W.C.?

johnp-the piping is straight forward, 4' straight out of the boiler, and then out 11' to the outside of the building, into a concentric vent, intake is more or less the same.

Tom-Lochinvar tech support is good, once you get to the second tier. At this point, one guy says mixture adjustment, the other venting, length, and or concentric itself. I am more or less convinced it is not mixture, and as Carl says, don't want to tear out the piping, to find it wasn't the issue.

john p_2

Can you post a pic of the gas piping at the boiler?

Tim McElwain

Another thing to try is actually disconnect the vent from the equipment and run it for a short time with out it. If the noise goes away you have found your problem. Then you have to figure out how to resolve it. Sometimes either a vent restrictor or in some cases a restriction on the combustion air intake. In either case you will have to re-configure your combustion setup with a combustion test.

ced48

I have lots of pictures, but none show the gas piping, I'll try to get one tomorrow.

Tim-I will try that if reducing the outlet does not work.

Zman

On the one I dealt with, the pressure,combustion,venting was perfect. The noise would not go away.
The propane company reluctantly switched the regulator and the problem was solved.
My understanding is that the diaphragm in the regulator creates a harmonic flutter that resonates through the boiler.
It is unusual and certainly not the first thing to try. You seem to be running out of solutions, which makes me think it may be worth a try...

Tim McElwain

Zman is correct but many times that is the result of being to close to the regulator. Regulator diaphragms are funny things if you place two of them too close together they will work off one another and make noise. The negative pressure gas valves actually work off a principle called "Zero Governor" which has been around for years in gas engineering also called the double diaphragm which results in typically zero pressure at the outlet of the regulator then some form of compressor or in modern Mod/Con equipment a combustion air blower or inducer will let us say suck the gas out of the valve.

ced48

I will try reducing the vent size, hopefully tomorrow, if that doesn't work, I think I'll give the gas company a call.

Does the fact that this condition always pops up at the exact same fan speed point to anything? I mean exact, when she hits 23 percent, it is going to whine. By 25 percent it's gone. Wind, outdoor temperature, operating temperature, does not matter. Same thing at 29 percent. It use to do it at 37-38 percent, but I've lowered my water temperature, and circulator speed, so it never gets there in a normal heating cycle, even a 0 degrees. Longer run times are great for overall comfort, and equipment life. This was the smallest, fire tube boiler out there, and although it's at least 60 percent oversized, I'm quite happy with my choice, except for a little whining, that with the help of all of you, I'm going to fix.

DZoro

Concentric vent especially in a horizontal position can be your issue. In low fire situations the exhaust can be real lazy and return in the intake. This will also cause premature failure of the venturi. What does the venturi look like, any black film, pitting, outside ring loose? If you get to the firing rate that it sounds off on, put you hand slightly over the intake, does the sound go away? If so change venturi, and extend exhaust pipe on the concentric vent. Also inspect fire cone, you mentioned a popping tone also? Bad cone can cause a popping noise.

icesailor

FWIW:

When you hear harmonic noises inside a Mod Con boiler, think of these bad boys. Air is blowing across something with some force and setting up some harmonic distortion. The job is to figure out what it is. Air or something is always the cause. In the case of the Andean Pan Pipe, it is the length of the tube and which tube you blow across that makes the pitch of the sound. How hard you blow across the a particular pipe will determine how loud it is. The pitch doesn't change. Some Pan Pipes will give chords because you blow across two pipes. Sometimes, if you listen carefully, you might hear more than one note.

Or so I have heard.

http://www.nativefluteswalking.com/panpipes-andean-american.shtml

ced48

Dennis said:

Concentric vent especially in a horizontal position can be your issue. In low fire situations the exhaust can be real lazy and return in the intake. This will also cause premature failure of the venturi. What does the venturi look like, any black film, pitting, outside ring loose? If you get to the firing rate that it sounds off on, put you hand slightly over the intake, does the sound go away? If so change venturi, and extend exhaust pipe on the concentric vent. Also inspect fire cone, you mentioned a popping tone also? Bad cone can cause a popping noise.

The fact that the whine happens even in dead calm weather, with the exhaust moving out and up and away, seems to make me think it is not the issue, but I am going to try removing the air intake pipe completely, and see what happens. No there isn't a popping sound, just a whine. The fact that it happens a only certain levels of fire, all the time, has got to point to something I'm missing. By the way, I have extended the vent out about 8", because of what you are talking about.

I tried reducing the exhaust vent size from 2", to 1 1/2" yesterday. It made things a little worse, louder whine, wider range. This more or less rules out lengthening the run as a solution. Maybe it is not getting enough air?

Ice-Yes I think I'm thinking along those lines, mostly because it always happens at the exact same firing levels.

icesailor

If you have an analyzer, run it with the intake ON then run it with the intake off, so that it isn't sucking through the outside. You might have to cut it, but you can reconnect it with Fernco or a No-Hub Coupling.

I worked on a 90+ WA furnace where the secondary heat exchanger was blocked. It was nuts. If I took the fresh air off, it would run, but the CO was instrument killing high.

Try really hard to understand how it works. Then, its easier to figure out WHY it isn't working. Someone earlier posted some really excellent points that they had discovered. When you put the 2X1 1/2 reducer on the exhaust, you changed the air fuel ratio drastically. The fact that it got worse tells you something. What it says is up to you to figure out.

ced48

Ice, yes I do have an analizer-

What it tells me is that lengthening the vent run isn't going to fix the problem. For the record, this fix was recommended as a strong possibility by a very respected Lochinvar guy, who told me to do this, as well as dump the concentric venting. Had I done this, I would have wasted a lot of time and money for nothing.

If this is pointing you in a direction, don't make me beg! Does it point towards insufficient air supply?

DZoro

On the right track with air.
Extension of exhaust on the concentric is great, especially if it is a horizontal install. Do you have a screen on the exhaust?
If you don't find a smoking gun with intake, take a look at the exhaust. Specifically at the base of the exhaust at the boiler. Not real familiar with that boiler but think it's similar to prestige H/E. If so take off the drain trap assembly and look carefully up into the exhaust tube, it should be fully open view to your first exhaust elbow? Check also the intake inducer wheel and venturi.

icesailor

I'm not playing games with you. I don't have answers for you. Just ideas.

What I was suggesting about an analyzer is to test throughout the firing range. From low to high and back down. So, if the numbers stay similar throughout the firing range, it tells you something. But if it wanders all over the spectrum, it might show an issue with the air fuel mixing ratio. You're on the cutting edge of technology. One early modulating gas boiler had issues with a brand of gas valve. It was hard tracking down the issues. But they were resolved.

Fixed rate fire burners on oil or gas are easy. One rate, one burn. One sound. Modulating burners have different sounds. Listen to the sounds. Between the sound and the DA readings, it will give you a clue. Great learning tool.

The owl has hearing so sensitive that it can hear a mouse or vole under the snow, in the dark, and swoop down, drive his talons into the snow and grab the Vole. You can listen to the combustion, you can hear water and steam going through a system. Your ears are as important as your eyes.

IMO.

Jack

Is this a new tank set? Sometimes on a new tank set, they load it up with percaptan (sp) and methanol and it can make things sing. Years ago I had this happen and the tech service was able to settle it down with an air/gas adjustment. It happened only on the new tanks sets with new heaters and not on all of them. It does have its own paragraph in the service manual all these years later.

As well years ago I had a "singer" on a water heater that I just could not figure out. I did everything I knew to do on it and was drawing Maggies Drawers on it. The vent was concentric and installed correctly with all specs correct. It was within a couple feet of an outside corner. Kinda out of "no other ideas" I was walking out of the basement and there was a manila folder laying there. I said, What the heck, may as well try it. I rolled it up and taped it onto the exhaust. fired the unit up and quiet as a church mouse. I guess it was something to do with the eddy currents coming around that corner. I was happy, but didn't feel real smart.

Ironman

I just came from another WHN085 that was fog-horning. Backing out the throttle screw to a richer setting solved it.

I've noticed that you can be on the richer end of Co2 and still back the throttle out without it going higher but the fog horn stops after you keep opening the throttle. Keep opening it til the noise stops, then check your Co2.

I believe the WHN055 has the same HX and burner as the 085, just a different orifice and fan programming. You might try experimenting a little based upon that (if it's correct).

Still, I would be pressing Lochinvar Tech Support to make it work right.

SWEI

Ironman said:

I just came from another WHN085 that was fog-horning. Backing out the throttle screw to a richer setting solved it.

Interesting. Any thoughts as to whether this might be related to the WH series' direct connection of combustion air piping to the fan inlet (as opposed to dumping it in the cabinet the way TT does)?

Ironman

Kurt,
I went the route of disconnecting the intake when I first started having the issue with the WHN. It made no difference. I tried everything that's been suggested here. Nothing worked. Backing out the throttle has worked on each one.

All of mine have been 085s or 110s, so I don't know if it's different with the 055 that ced48 is dealing with.

SWEI

Good info -- thanks, Bob.

It's starting to sound like there's some kind of resonance in the internal boiler parts. Most VFD's have ways to program "skip frequencies" to avoid this behavior.

Ironman

ECR had this same issue only worse with its first aluminum block mod/con. I spent over a hundred hours trying everything imaginable to correct it on four boilers I had installed. The problem there was it was very random and not easy to re-create when on site. They came out with a resigned burner and some different parameters which totally cured it.

To their credit, they compensated me for my time.

ced48

john p said:

Can you post a pic of the gas piping at the boiler?

Sorry these pictures don't show the piping that clearly, but everything is squeezed in tight. Maybe between the two photos, you can put it together-

ced48

Ironman said:

I just came from another WHN085 that was fog-horning. Backing out the throttle screw to a richer setting solved it.

I've noticed that you can be on the richer end of Co2 and still back the throttle out without it going higher but the fog horn stops after you keep opening the throttle. Keep opening it til the noise stops, then check your Co2.

I believe the WHN055 has the same HX and burner as the 085, just a different orifice and fan programming. You might try experimenting a little based upon that (if it's correct).

Still, I would be pressing Lochinvar Tech Support to make it work right.

Bob- Have you ever heard these boilers whine, rather than fog-horn? I think the different sound points to a different cause?


As you adjusted the mixture richer, did the sound go away gradually, or all of a sudden stop?

ced48

Jack said:

Is this a new tank set? Sometimes on a new tank set, they load it up with percaptan (sp) and methanol and it can make things sing. Years ago I had this happen and the tech service was able to settle it down with an air/gas adjustment. It happened only on the new tanks sets with new heaters and not on all of them. It does have its own paragraph in the service manual all these years later.

As well years ago I had a "singer" on a water heater that I just could not figure out. I did everything I knew to do on it and was drawing Maggies Drawers on it. The vent was concentric and installed correctly with all specs correct. It was within a couple feet of an outside corner. Kinda out of "no other ideas" I was walking out of the basement and there was a manila folder laying there. I said, What the heck, may as well try it. I rolled it up and taped it onto the exhaust. fired the unit up and quiet as a church mouse. I guess it was something to do with the eddy currents coming around that corner. I was happy, but didn't feel real smart.

Jack- The tanks have been in place for nearly two heating seasons, filled a few times, with the whine staying the same.

So, you lengthened the exhaust?

icesailor

Maybe you don't get the connection with the Pan Pipes. Each pipe is a tube, sealed at the bottom. You blow across the top of the tube or pipe. The length of the pipe determines the pitch of the sound, which is just osculating sound waves from the air in the pipes vibrating. @Ironman: describes the same issue. You can make a Pan Pipe set with glass bottles and get different pitches by the amount of liquid in the bottle. Try blowing across an open beer bottle. Try when it is half full. Then, empty.

IMO, if the sound is deep, it is the sound of the flame resonating around inside the boiler. If it is high pitched, it is the sound of the air passing over something that causes it to whistle. Changing the volume or velocity of the air, changes the pitch. Changing the air/ fuel ratio has an effect on the pitch because it will change the flow characteristics. Like blowing on a trumpet. You make your lips vibrate while blowing in the mouthpiece. How you blow, changes the notes.

Like Ironman pointed out, he spent over 100 hours working on the issue and the factory solved it. It doesn't do it on other boilers. It is a manufacturing and design issue.

You shouldn't have to set your combustion parameters around a design noise inside the boiler. You should be able to go for the best numbers you can get. Not the quietest.

FWIW.

ced48

Ice- I do get what you are talking about, and I think you are right on as to what is going on-My point with Lochinvar has been just what you are saying, why should I have to run the boiler at combustion levels outside of their own parameters? Even doing that hasn't helped the problem. I will keep messing with this thing-Warmer weather is coming, and the problem will be gone, till next fall--

icesailor

ced48 said:

Ice- I do get what you are talking about, and I think you are right on as to what is going on-My point with Lochinvar has been just what you are saying, why should I have to run the boiler at combustion levels outside of their own parameters? Even doing that hasn't helped the problem. I will keep messing with this thing-Warmer weather is coming, and the problem will be gone, till next fall--

Listen to what Ironman said.

The "Fix" is beyond we mortals. Let their R&D solve it. It could be something as stupid as the material that holds the gas flame in place. How would you fix that?