Harmonic Combustion Noise

ced48

I have to listen to this thing "sing", it's in my den. If it was in the basement, different story-

DZoro

another thing to try. If you have a extra screen metal or preferably a plastic with 1/4" openings, install in intake , like where you put in the fernco? I would make a note saying screen installed if it does work! Also one in the exhaust if you don't already have.
Worth a shot, good luck!

ced48

Dennis-I'm a little slow sometimes, by doing this, are we decreasing air flow? I thought my reducing the exhaust outlet accomplished this with negative results. Maybe I'm missing something?

icesailor

OK.

Junior saves his money from working at Micky Dee's after school for minimum wage and buys an affordable ride that looks cool and has a cheap 4 cylinder engine. Its quiet and no one notices him driving. He wants to impress his friends. So he goes out and buys himself the biggest trumpet exhaust his Micky D money can buy. A great big resonator muffler that resonates the sound of every cylinder in that 4 cylinder motor. Junior starts off down the street, that runs along the freeway and matts it. The Red Line on the tachometer says 5600 RPM But Junie wants to hear what it sounds like at 7,000 RPM's. LOUD!!. But when he hears the valves floating and beating on the top of the pistons, he backs off on the gas. Then, as the RPMs drop, the exhaust now sounds like a pack of firecrackers going off. All combustion devices are just a form of air pump. A boiler is an air pump. It takes in fresh air, compresses it as it fires it, expands it, and exhausts it. You're listening to the sounds of expanding gasses.

I'd turn on houses in the spring. Light the pilots and run the burners. I'd be venting air out if the gas lines. Sometimes a gas burner would "Backfire" onto the mixing chamber and make a heck of a roar. Shut it off and light it again. Once the fuel stabilized, it was fine. Its inside.

20 years ago, if you installed a Weil-McLain VHE and it made a noise like that, and Weil-Mclain said you had to go out and buy a $2,000 analyzer to shut it up, you'd be switching boilers.

When they started coming out with these oil boilers with wet bases and no refractory rugs, and run as cold start, they smoked like an old wino with a new carton of Camels. Once hot, they stopped. "Absolutely no need of any kind of "rug" in the bottom of this boiler. Absolutely NOT!!!". When those of us who had been around, put rugs in to reflect the heat back into the flame so it wasn't cold. the smoking went away magically. And they were quiet when they smoked. Noisy when they weren't.

Its an internal issue. Tell them you want one that doesn't whistle. If a new one doesn't whistle, it's either that there was a change inside, or something was seriously wrong with the one you have.

ced48

God, Ice, I love your perspective-I get frustrated now and then, and kind of tell them just that down at Locheville. The last time, they offered to pay someone smarter than me to fix the the darn thing. One problem, I had to find that guy. I'll be darned if I can find someone who seems to have more of an understanding of these boilers than I do, to come out, look ,and listen to this little cry baby. Heck, it's most likely just the opposite, they are all smart enough to know they can't shut the darn whistle off-Hey, if anyone in the RI area is interested, let me know-

DZoro

The thought with the bird/rodent screens is not to decrease the air flow, but change it. Similar to what Ice said about the flutes, but in a more boring way of describing it!
Some systems, I believe Rheem, had originally come with a divider to be installed in the pipe. That was for a different reason, but similar. Just trying to change the air flow pattern inside the pipes.
Again just throwing stuff out there .WAGing it.

Ironman

ced48 said:

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?

It was fog-horning and went away fairly quick when I hit the right spot.

I agree that you shouldn't be outside the parameters and I haven't been on any of them. I was just near the high end. And, I'm sure there's probably some wiggle room that they don't tell us about. But this is clearly something that Lochinvar should address if it can't be cured with adjustments.

Two other things to check:
1. Do you have flex connector in the gas line? That can cause this.
2. Is the gas cock a full port valve or reduced port? It needs to be full port.

bmwpowere36m3

Interested in results… since I'm hanging a WH055 as we speak.

@ced48 did you originally have a concentric vent installed? My boiler came with the side termination plate (side x side). I was planning on running 2" CPVC/PVC.

ced48

Dennis said:

The thought with the bird/rodent screens is not to decrease the air flow, but change it. Similar to what Ice said about the flutes, but in a more boring way of describing it!
Some systems, I believe Rheem, had originally come with a divider to be installed in the pipe. That was for a different reason, but similar. Just trying to change the air flow pattern inside the pipes.
Again just throwing stuff out there .WAGing it.

Okay, that makes sense, and I will give it a try.

ced48

bmwpowere36m3 said:

Interested in results… since I'm hanging a WH055 as we speak.

@ced48 did you originally have a concentric vent installed? My boiler came with the side termination plate (side x side). I was planning on running 2" CPVC/PVC.

It has always been vented concentric, I liked the smaller footprint on the side of the building, and the pre heating of the combustion air.

ced48

"Two other things to check:
1. Do you have flex connector in the gas line? That can cause this.
2. Is the gas cock a full port valve or reduced port? It needs to be full port."

Bob- No flex connector, but yes, it has a reduced port valve. I used it because it took up a little less space, and I wasn't concerned about gas flow, 3/8" would be more than large enough for what my unit would demand.

I guess I could close the vale down a bit, and see if the sound changes. If it does, then I would swap it out with a full port. Gees, as much as I want to fix this thing, I don't look forward to changing it, just no room to work.

bmwpowere36m3

ced48 said:

bmwpowere36m3 said:

Interested in results… since I'm hanging a WH055 as we speak.

@ced48 did you originally have a concentric vent installed? My boiler came with the side termination plate (side x side). I was planning on running 2" CPVC/PVC.

It has always been vented concentric, I liked the smaller footprint on the side of the building, and the pre heating of the combustion air.

I see, I prefer the look of the side by side as it very slim (maybe 3"
thick, 14" wide, 9" tall).

This

vs.

ced48

But it is 8+ inches wide, and doesn't fit between a single course of siding, unless the siding is wider than 8 inches.

A coat of paint on that vent, and a little neater job of cutting the opening, it would almost not be noticeable.

Ironman

ced48 said:

"Two other things to check:
1. Do you have flex connector in the gas line? That can cause this.
2. Is the gas cock a full port valve or reduced port? It needs to be full port."

Bob- No flex connector, but yes, it has a reduced port valve. I used it because it took up a little less space, and I wasn't concerned about gas flow, 3/8" would be more than large enough for what my unit would demand.

I guess I could close the vale down a bit, and see if the sound changes. If it does, then I would swap it out with a full port. Gees, as much as I want to fix this thing, I don't look forward to changing it, just no room to work.

Closing it may compound the problem. The issue is that the reduced port causes a pressure drop that's unwanted with a negative pressure gas valve. Manufacturers have found that these can cause the harmonic noise that you're experiencing and they're saying to use a full port valve.

ced48

Bob-That is what I was thinking, if closing down the valve makes the problem worse, then there is a good possibility that the restriction caused by the fully open, but constricted vale, is the culprit. If it makes no difference, it's probably not the issue?

Ironman

It may not make it worse when closing it down. But that wouldn't mean it's not the cause.

We're dealing with negative pressure gas valves that are for the most part new technology for our industry. The have their own peculiarities, many of which have, and are, being discovered in the field. We can't confine our thinking to the nuances of the conventional gas systems that we're accustomed to. As you clearly understand, this is a harmonics issue, not a lack of pressure or gas volume. If a manufacturer told me that they had discovered that a reduce port gas cock can cause this, then I'd remove it rather than try to diagnose it with a testing method that I had thought up. I had a manufacture emphasize this very thing in a training class this week.

ced48

Bob-I agree with your thoughts, and appreciate your help. I will change out the valve, and see what happens.

icesailor

When Munchies came out in the 1990's, they had a 1/2" gas valve, a nipple and a 1/2" X 3/4" Increaser for the gas connector. The I/O manual said to connect the boiler with full size 3/4" IPS with a full port valve. They ran fine. Smarter installers that removed the increaser and connected them as 1/2", often discovered they had problems. And these were on 80,000 LP models. They wanted full size (3/4" from the regulator with no branches.

Ironman

Changing the gas cock may not solve the problem, but you'll never know unless yo do. Considering that you've tried everything else that's been thought of, and that a gas cock is very cheap, I think it's only logical to see if that's the issue.

SWEI

I think Chris might have the best idea here. The incremental cost of a 3/4" full port valve and a nipple is what, $3 retail?

We have seen reports here of gas problems solved with a length of fat gas pipe which acts as an accumulator, but I wonder if some of those might merely be acting more like a detuning slug. Resonance in mechanical system can be a real bear to track down.

ced48

I still feel the fact that the noise only occurs when the fan is running a certain rpm's is a big clue to this mystery. I wish there was a way to run the fan, without fire, at a chosen rpm. If this is all related to incoming gas pressure drop, ect, does it not make sense that it would happen at 30 percent sometimes, rather than never, and always at 29 percent? You guys have a lot more experience than I, so trust it could be the shut off valve. Last night I closed the vavle slowly, until the boiler shut down for no gas, no sound difference. And I agree with Bob, this does not prove anything. Nor does the fact that I have a constant 11 W.C., at all firing levels.

I have asked my guy a Lochinvar to check with engineering to see what they think of the valve issue.

I would just go ahead and change the valve, but I have to pull a circulator, and drop the gas line down to do this. I have tried so many things, so I am hesitant to jump in and do this-but I probably will-

To refresh. This is the second fan on this unit. The first made a lot more noise than this one. I may see if I can get them to send me another, and clean the HX at the same time, at least gaining something for my time, a clean HX.

Unrelated, I hope, I'm trying to get them to tell me what the "coffee grounds" consist of, and why they form-

icesailor

You and some others need to look at the gas piping like a Warm Air furnace. They need a large supply and return plenum to get the air organized for their trip out into the system, and back into the blower in the furnace. Same as those great big pipes on a gravity hot water system.

If you had only a 8" round return connected directly to the back of your WA furnace and a 10" round duct on a flat plate on the outlet, it would work. Just not as well as it is supposed to. Restrictions are funny things. In NASCAR, on the really big and fast tracks, the cars were going too fast, and they were actually flying. To slow them all down equally, they require "Restrictor plates" on the intake manifold. Everyone gets to take in the same amount of air. How they mix it is the option. "Restrictor Plate Racing" is boring. All the cars have the same HP and no one has the nuts to pass anyone unless they can draft.

Like I said before, early Munchies had people taking the 1/2" X 3/4" increaser off and piping the gas with 1/2". Or connecting to a 1/2" gas supply line to a whole house, with the Munchie at the end of the line, piping to the boiler with 3' of 3/4" IPS pipe (off the 1/2" and sending the bill. When it didn't work as advertised, "others" re-piped it as the I/O manual said. Full 3/4: from the source.

If the replacement of the fan changed the sound, there must be some issue with the fans, One fan should be the same as another. Most gas and oil burners have a pre purge and post purge where the fan runs without the gas running and burning. If the noise occurs at 29% (whatever that is), and it is trumpeting, while trumpeting, close the gas valve. If the trumpeter stops playing, it's the combustion.

Or so it would seem. The combustion is like blowing harder in the trumpet. Which makes it louder. Listen outside. Depending on your hearing sensitivity and range, you can tell a lot. If you have spent quality time in "Boom Cars", ruining your hearing, and forcing people to listen to the bass vibrations in their houses as you pass by, you might have a hearing sensitivity that you aren't aware of. Sometimes, you can hear a good boom car from a quarter of a mile away.

And they have all the window rolled up to get the full benefit of that $2,000 sub-woffer they have in the trunk with the big speakers.

ced48

Got a new guy at Lochinvar, seems to have a lot of understanding of his product. Wants to try adjusting the combustion numbers one last time. I'm going to give this a try with him next week. Will post how it goes.

Ironman

Again, it's not a pressure issue but a resonance issue. It happens in electrical and electronic circuits also.

Think in terms of water flowing evenly in a stream. Now, put a tree branch into the flow. The volume of water is still there, but there are ripples of current produced in multiple directions. That's what's happening with a reduced port valve to the flow of gas.

Anything in the circuit that disrupts smooth flow can cause harmonics. The throttle screw is just an impediment to flow in the gas circuit. That's why opening it up can cause the noise to cease.

Stop thinking pressure and think flow disruption. Running the fan without gas or ignition won't produce the noise.

icesailor

@Ironman:

Awesome comment!

My point was that if the noise stopped with the flame was burning, it was a flame connected noise.

"" Stop thinking pressure and think flow disruption. Running the fan without gas or ignition won't produce the noise. ""

bmwpowere36m3

@Ironman

I see most valves marketed as gas valves are reduced port, like this: Webstone IPS Valve. I see that regular full-port ball valves like ones used on water lines are gas rated as well, they would be okay to use? Are those what you're referring to?

SWEI

ced48 said:

I still feel the fact that the noise only occurs when the fan is running a certain rpm's is a big clue to this mystery. I wish there was a way to run the fan, without fire, at a chosen rpm.

Are you sure you can't do that from the installer menu on the WH? Pretty sure I can with a TriMax TT...

ced48

SWEI said:

ced48 said:

I still feel the fact that the noise only occurs when the fan is running a certain rpm's is a big clue to this mystery. I wish there was a way to run the fan, without fire, at a chosen rpm.

Are you sure you can't do that from the installer menu on the WH? Pretty sure I can with a TriMax TT...

I'm pretty sure I can't, but I will check again. I just found out yesterday from Loch technical, that I can choose any fan speed, when in service mode, so we can try to adjust the boiler when it is making the noise. Until now, it has been done in a hit or miss approach, because no one down there, that I had talked to, was aware of this capability.

Ironman said:

Again, it's not a pressure issue but a resonance issue. It happens in electrical and electronic circuits also.

Think in terms of water flowing evenly in a stream. Now, put a tree branch into the flow. The volume of water is still there, but there are ripples of current produced in multiple directions. That's what's happening with a reduced port valve to the flow of gas.

Anything in the circuit that disrupts smooth flow can cause harmonics. The throttle screw is just an impediment to flow in the gas circuit. That's why opening it up can cause the noise to cease.

Stop thinking pressure and think flow disruption. Running the fan without gas or ignition won't produce the noise.

Bob-I understand the flow issue, but I am still skeptical that that is what is going on here, because of the precise nature of the occurrences. Yes, this is a stupid question, Im sure, but why does it never happen at any other rates? Like I said, I'd just change the valve but it is a pain in the ---

I'm going to let this guy try and tune it out, if it doesn't work, I will discuss the valve issue with him at that time. Please don't take offense at my dragging my feet at changing out the valve, I do believe it is a good possibility that it could be the culprit. If it is, you can tell me I told you so-LOL-

bmwpowere36m3 said:

@Ironman

I see most valves marketed as gas valves are reduced port, like this: Webstone IPS Valve. I see that regular full-port ball valves like ones used on water lines are gas rated as well, they would be okay to use? Are those what you're referring to?

Any valve marked WOG, full port, will work-

bmwpowere36m3

@ced48

If you can post the procedure on adjusting fan speed in service mode that'd be great. I understand that it typically ramps from min to max fire and stays at max fire.

bmwpowere36m3

bmwpowere36m3 said:

@ced48



If you can post the procedure on adjusting fan speed in service mode that'd be great. I understand that it typically ramps from min to max fire and stays at max fire.

@ced48

Did you ever find out the procedure?

ced48

Place the boiler in service mode. When high fire is achieved, use the scroll knob, and go to fan speed. Press the knob in once, then scroll down to the desired speed. Press save, and then home. You can go to any other speed you desire by repeating the process.

keyote

My KHN 085 drove me crazy wih a sound, thought it was air in water, thought it was combustion issue turned out the sealed condensate trap has a ball that floats up to release condensate then is supposed to come back down to rest on a rubber washer thats seated in a indent. except they used a paper backed double sticky to glue it into its seat and the condensate dissolved it so the washer kicked around and kept the ball from reseating so at low fires when not enough condensate to flood it the flue gasses would escape through it and bugle. so far some silicone is holding it down