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Photograph of  a modern oil-fired heating boiler Oil Burner Rumbling Noise Cause & Cure

Rumbling or Pulsation may be Normal, Abnormal or even Dangerous

Oil burner rumbling noise or sound troubleshooting:

Some oil burner noises are normal, others including loud rumbling indicate trouble and may even be dangerous. The rumbling oil burner noise discussed here may also be described by some people as oil burner pulsing or oil burner pulsating.

This article series explains how to recognize & diagnose the cause of oil fired heating boiler noises, leaks, odors, or soot and smoke.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

How to Diagnose Loud Rumbling Noises During Oil Burner Operation

Oil burner schematic (C) Carson Dunlop AssociatesCommon causes of rumbling oil burner noise

These causes of oil burner rumbling or pulsating noise are given roughly in order of probability.

Question: loud thundering noise after replacing old oil burner.

2019/11/16 Chuck said:

I installed a new Weil-McClain WGO4 oil burner to replace the 21 year old same model.

This unit makes loud thunder noise while running.(flame noise ?)

Is this normal for a newer model?

The sketch above is provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ]. [Click to enlarge any image]

Reply: Oil Burner Rumbling Noise Diagnosis and Repair notes

Some noise is normal however, but the normal sounds tend to be more smooth and continuous.

But an increased rumbling noise can be a sign of burner, combustion chamber, or even chimney problems.

Newer oil burners will be somewhat louder than much older models for both good reasons to tolerate and bad ones to correct.

But if the rumbling is due to poor oil burner operation or the choice of the wrong burner model or tube length or burner nozzle those errors can make the system unsafe.

Start by confirming that the oil burner model including tube length, spray pattern, turbulator design are proper for your boiler or furnace combustion chamber.

Continue by making sure that the system is properly adjusted and tuned. Measure the system standard heating tuneup parameters including smoke and CO2 to verify that your adjustments have improved, not hurt, system performance.

Good oil burner noise

Some steady rumbling noise at a properly cleaned and adjusted oil burner is normal, but there are things a technician or homeowner can do to reduce the creation of those sounds or to reduce their transmission to the building interior, such as sound-insulating the boiler or furnace room walls or ceiling (with appropriate fire-resistant materials).

We have also had good success at reducing rumbling noises at older oil burners by changing to a Monarch AR oil burner nozzle of the proper size or an equivalent "anti-rumble" burner nozzle from other manufacturers. Often we also found better combustion efficiency using hollow-cone oil burner nozzles that can be more quiet.

See OIL BURNER ELECTRODES for details.

Some oil burner motor noise that's normal is also called "rumbling" or "roaring" by some of our readers Newer oil burners use a motor that spins at 3450 RPM ("high speed burners") that permits more-efficient oil burner operation while older burners used a motor that ran at 1725 RPM ("slow speed burners"). The newer motors are often a bit louder and whinier than the old ones.

But that noise difference is generally tolerable. Some readers described the motor noise as rumbling though in my opinion it's not.

Bad oil burner noise

Any oil burner, if not properly adjusted or selected for the combustion chamber into which it's being fired will not work properly and may produce loud flame / burner noises, particularly a rumbling sound.

Watch out: loud rumbling noise at the oil burner could be a sign that the burner (or if you're lucky just the nozzle) is the wrong model:

d if the flame is too long, for example due to a too-long oil burner tube that projects too far into the chamber, or a nozzle that produces a flame that is too long rather than shorter and wider, that can cause incomplete combustion, poor operation, rumbling, sooting, and even risks a

dangerous OIL BURNER PUFFBACK EXPLOSION

So first off ask your heating oil technician - who knows more than you or I do - to check the oil burner model and oil burner tube length, nozzle spray pattern, nozzle gph rate, and oil burner tube turbulator end all against the boiler or furnace combustion chamber design and specifications in the boiler/furnace IO (Installation and Operation) manual and on the oil burner itself and its specifications.

IF all of those specifications match (I suspect they don't) then you might ask about an AR nozzle as I'll explain:

Now oil burner rumbling noise isn't new and in fact some oil burner nozzle manufacturers include an "AR" nozzle model or "Anti-Rumble" nozzle. Sometimes I used to stick on an AR nozzle and my clients would notice that the flame and burner were noticeably more quiet. So you should ask your oil burner technician about this options.

Some heating system and heating oil burner noises are considered normal.

Reader Question: What is causing a rumbling sound whenever the furnace kicks on

We had a furnace installed in December. Since then we have a rumbling whenever the furnace kicks on. The rumbling vibrates the entire house. The installers have been to the house three times and cannot locate the problem.

Moderator reply:

The cause, diagnosis, & cure of rumbling sounds at the oil fired heater are discussed in detail

at OIL BURNER RUMBLING NOISE

Rumbling at the oil burner may be normal but often indicates improper adjustment, need for cleaning or service as we discuss in the article OIL BURNER NOISE SMOKE ODORS - home

Watch out: some of these conditions can lead to a dangerous OIL BURNER PUFFBACK EXPLOSION

Chimney fires: Watch Out: DANGEROUS, IMMEDIATE ACTION NEEDED: Very loud noise like a roaring freight train coming from a chimney is likely to be a chimney fire- extremely dangerous, risking a house fire: turn off heat as you run out of the house: call the fire department from your cell phone or from a neighbor's house.

See CHIMNEY INSPECTION DIAGNOSIS REPAIR for details of chimney inspection, diagnosis, and repair

Fixing Oil Burner Rumbling Noises

First let's name the "normal" noises at an oil burner.

Oil burner noise is that is normal tends to be more smooth and continuous, without rattles, bangs, significant vibration or rumbling or stumbling.

Of these noise components, the oil burner flame or combustion noise is usually the loudest "normal" noise coming from an oil burner.

The electric motor powering the oil burner's blower and fuel unit also may generate some electric motor noise and there may be a bit of vibration that can be transmitted into the building through piping or other heating system components.

The fuel unit pumps heating oil to 100 psi or higher, then sprays it through an oil burner nozzle where the oil is ignited by electrodes mounted in the oil burner's tube at the entry to the combustion chamber.

The "roar" that you hear at a normally operating heating system oil burner is usually produced mostly by this combustion process.

Our complete catalog of oil burner noises is at OIL BURNER NOISE / ODOR DIAGNOSTIC INDEX

Here we focus on oil burner rumbling, stumbling, pulsing noises.

Oil Burner Rumbling Diagnostic Questions

  1. Has the oil burner noise changed?

    Changes in the noise from your oil burner, including an increase in volume or a change in character, including hearing rumbling, stuttering, pulsing, banging, etc. all can indicate an abnormal and even possibly unsafe condition.

    Has the oil burner been changed for a new, higher-speed model?

    Motor speed affects oil burner noise level. Burner operating noise will be louder at new high-speed oil burners whose motor runs at twice the RPM (3450) as older burners; doubling the burner speed along with concomitant higher oil and combustion chamber pressures increase noise levels.

    Careful selection of oil burner nozzle, flame retention head and head settings may reduce this noise a bit.

  2. When does the oil burner noise occur?

    2.1. Rumbling noises at oil burner startup  (which usually continues all during operation" or a "stumbling" sound in the combustion chamber probably indicates that the system needs inspection and cleaning very soon.

    Start-up rumbling noises are most-often from draft problems, from a bad combustion air setting, or from some dope having removed the turbulator from the oil burner head; Details are included later in this list.

    Watch out: if you hear a bang! sound or a loud whomp! when the oil burner is starting that may indicate the ignition of accumulated unburned fuel in the combustion chamber. Because puffbacks can be caused by a variety of problems (oil piping line leaks, dirty oil burner nozzle assembly, fuel or combustion air problems, simply failure to maintain the system) a trained service technician is needed.

    If you have not already had a messy and destructive puffback explosion one is quite possibly imminent. The need for oil burner service is urgent and the system may be unsafe.

    See OIL BURNER SOOT & PUFFBACKS

    2.2. Rumbling Noises at oil burner shut-down - stumbling  after the oil burner motor has stopped, indicate that oil is continuing to leak into the combustion chamber and risks a dangerous puffback - see "Noises during oil burner startup" above. Immediate service is recommended.

    Shut-down oil burner rumbling noises are usually traced to air leaks into the oil piping system (expanding air as oil pressure falls pushes more air out of the nozzle for incomplete combustion), improper electrode settings, or a defective fuel unit (oil pump) that doesn't shut off cleanly.

    See OIL SUPPLY LINE PIPING LEAKS

    and OIL BURNER ELECTRODES

    Watch out:  if you see soot or smoke or smell combustion gases, possibly accompanied by an increase in oil burner or heater noise, the system is not operating properly and may be unsafe.


    2.3. Stumbling or more-regular Pulsating noises at the oil burner during operation
    are usually caused by

    too much combustion air (discussed below),

    bubbles in the oil from air leaks into the oil piping system or from gasification caused by forcing the pump to lift the oil too high (from a buried tank or from a lower floor), or less common,

    by having installed the wrong burner model or burner tube or head or firing rate for the heating appliance and its combustion chamber.
  3. Check the oil burner draft and chimney:

    A dirty or blocked chimney, a dirty or blocked heat exchanger in the boiler or furnace, or an improper combustion air inlet setting can cause draft problems that lead to rumbling.

    If the draft is too weak or low the heating system may run with backpressure and may run smoky due to incomplete combustion, causing sooting and heat exchanger blockage and rumbling. Check first for obvious snafus like a chimney cleanout door left open or obvious thick soot clogging in the breech viewed through the barometric damper; Check that the damper is operating freely.

    If the draft is too high the system may run too hot, sending much of your heating money up the chimney. Check for a misadjusted barometric damper or a lost chimney cap.

    Typically we want to see about 0.2" WC over the fire and about 0.4" WC of draft in the breech.

    See DRAFT MEASUREMENT, CHIMNEYS & FLUES

    and DRAFT REGULATOR, DAMPER, BOOSTER

  4. Check the oil burner combustion air setting: at the oil burner air inlet. Typically the oil burner combustion air is set to just a trace of smoke.

    Service technicians will measure the O2 or CO2 level to permit fine-tuning of the combustion air.

    For example Beckett's service manuals generally advise increasing the combustion air inlet enough to drop the CO2 level from that measured at "a trace of smoke" down 1 or 2 percentage points, or to increase the O2 by 2-3 percentage points.

    See OIL BURNER SMOKE TEST

    See COMBUSTION AIR REQUIREMENTS

    and for newer buildings and small utility rooms or air-tight locations

    see COMBUSTION AIR for TIGHT BUILDINGS

    Watch out: even a small amount of dirt on those curved blades of the squirrel cage fan blower assembly can significantly cut the air flow produced by the oil burner's air intake system. Check and clean dirty blower fans.

    See BLOWER FAN ASSEMBLY CLEANING where we illustrate this same problem in an air handler.
  5. Check the oil burner head for obvious visual defects: these include

    Lost or removed turbulator or "air guide" that was originally installed

    Soot build-up at the nozzle and electrodes, preventing proper firing, caused by lack of maintenance or by other problems in this list, including more subtle problems like a leaky nozzle adapter or a cracked electrode insulator.

    Loose or improperly-adjusted electrodes also will cause improper combustion. The electrode gap as well as the location forward the proper distance from the nozzle face as well as location at the proper height above the nozzle opening all must be set correctly.

    See OIL BURNER ELECTRODES
  6. Check for oil or air leaks at the burner, in the oil line piping, and any other OEM gaskets or seals on the burner that may have been removed or damaged; air leaks can prevent proper combustion and can lead to a puffback.

    Also see OIL BURNER OPERATING TROUBLE
  7. Check the oil burner motor if the motor has been replaced, to be sure it's a design approved by the manufacturer. Some replacement oil burner motors whose vent openings are outside the blower wheel can cause improper oil burner operation by reducing static pressure in the combustion chamber.

    See also OIL BURNER MOTOR NOISE for signs of motor trouble

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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

Reader Question: Rumbling Oil Burner Noise Question: Oil burner noise: What is causing a rumbling sound whenever the furnace kicks on

We had a furnace installed in December. Since then we have a rumbling whenever the furnace kicks on. The rumbling vibrates the entire house. The installers have been to the house three times and cannot locate the problem.

They changed the flapper and added some vent work. The last time they came they thought we needed to change our oil tank. - Nancy Plummer

(Nov 18, 2017) Anonymous said:

We moved up north last year, and not used to oil burners so forgive my ignorance. It is an old unit, and we had a full servicing/cleaning 2 weeks ago. (He said everything was working although it's old)

It's starting to get cold and we just started to turn it on. Now I am noticing whenever the heat kicks on, sometimes there will be a periodic dull/low rumbling we can hear from upstairs. (Not sure if it's related, but the flap of the draft regulator (on the stack) will blow in every time it rumbles).

Last winter we didn't have this problem. Does anyone know what it might be (if it's dangerous) from this limited information? If it's just a noisy heater I can live with that.

Reply: rumbling oil tank or rumbling oil burner?

I'm not sure how an oil tank would cause rumbling in an oil fired heating system, except indirectly: if the oil tank were badly contaminated with rust and sludge it could cause repeated oil burner nozzle clogging and improper oil burner operation.

I'd ask the oil heat technician to be more specific about why they made that recommendation. [Incidentally oil burner noise does vary with the nozzle brand, size, and pattern.]

It is fair to say that some causes of bad oil burner operation can be difficult to track down and can be subtle.

A temperature sensor used by the aquastat and improperly installed can, for example, lead to short on cycling and sooty operation that leads to rumbling and bad flame, or a defective or clogged chimney can also cause improper operation - the list is pretty long.

From your note I can't tell if the sound source is improper burner operation, improper blower operation on a furnace air handler, or a duct work problem.

It might help to give a call to your oil heat service company and speak with the service manager. Ask him or her to send an experienced senior technician to review the problem so that your system is not only quiet, but reliable and safe.

Rumbling sounds at the oil burner itself are often a flame adjustment or a less than optimum choice of oil burner nozzle, as we also discuss in the

article OIL BURNER NOISE SMOKE ODORS

Anon,

Some rumbling noises on oil heating systems are normal. That is the oil burner is by no means a silent machine.

However loud noises, or changes in the sound from the way the system was running after your service person had cleaned and adjusted it could be signs of trouble.

And a noise like a freight train or very loud could be a sign of a dangerous chimney fire.

If I were worried about that I would dash outside and look to see if black smoke was coming out of the chimney.

If that were the case I would get people out of the house and call the fire department. So short of a chimney fire or a significant change in the system performance, or black soot or smoke blowing into the occupied space, you're probably not facing an emergency.

I would still ask the service person to check out the oil burner operation, particularly if the noise has changed. Sometimes the tech will simply need to change to an AR nozzle - an anti-rumble oil burner nozzle that can reduce the burner rumbling sound level.

(Nov 21, 2017) Jcurrie said: backfire after furnace shuts off is that dangerous ?

Backfire every time oil furnace shuts off after heating . Not running the furnace fan on continuous just on auto . No odour no spit etc but the backfire after furnace shuts off is that dangerous ?

Reply:

Yes.

With just a smidgen of information I can only guess that your oil burner is not shutting down correctly and is dribbling some in completely burned fuel into the combustion chamber the end of a heating cycle. That's risking a dangerous puffback explosion.

There could be several causes such as a leak in the oil lines, air in the system, or a fuel shut off valve that doesn't close properly in the oil pump.

You need help from a oil heat service technician.

Watch out: See OIL BURNER SOOT & PUFFBACKS

On 2016-09-03 by (mod) - a mechanics' stethoscope can help

Sometimes a mechanics' stereoscope can help find the noise source: motor vibrations can be transmitted via piping, for example. ALso check for a combustion problem or a chimney hazard. Sounds like a safety concern that merits a service call.

On 2016-09-03 by Jeff

Tankless oil burner used to heat the house and provide hot water. It is summer, so no heating.

When we call for hot water, the burner sounds normal when right at the burner, but there is a loud, continuous rumbling noise that you can really only hear upstairs in one of the bedrooms.

Getting complaints from the occupant! My daughter. Been doing this for years. I keep looking around but coming up empty. Any ideas?

On 2016-03-14 by (mod) re: noisy oil burner startup - rumbling burner

Todd

You may have a combustion air problem, the wrong nozzle pattern or size, or another mis-adjustmen

t. Unfortunately it's no longer possible to properly set up an oil burner by eye and spit - a bit of training and use of CO2, stack temperature, and smoke measurements are also needed.

On 2016-03-13 by todd

burner rumbles on initial firing then quiets down. i have a new nozzle and filed electrodes to a sharp point and adjusted .

On 2015-03-20 by Rumbling noise

Same spec nozzle - sure.

AR - don't know, probably not, he just keep replacing nozzles like a gloves.

Tracking - combustion chamber, some kind of misfiring.

Stethoscope will render you effectively deaf, half of the house vibrating and can be heard all the way from across the street.

And it is sporadic, thus cycling power does not really lead to constant replication of malfunction, usually turning power off and then back on solves the problem. I'm not taking chances and trying to shut it off as soon as possible.

On 2015-03-19 by (mod) -

Rumble

Was the nozzle replaced with the same spec as original? Did the service tech try an AR (anti rumble) nozzle?

Has the noise been tracked down at all?

Try a mechanic's stethoscope on the external parts when the burner is starting up: motor, blower, fuel unit, side of boiler, flue.

On 2015-03-19 by Rumbling noise

Well, going back to rumbling noise. Nozzle was replaced so far three times, filter cleaned, etc.

Still sporadically upon start up burner trying to take off like a helicopter, in fact it does sounds like a helicopter in the basement, after few seconds of operation it does quiet itself and going to normal sounds of burning flames, or if I'm fast enough - cycling power will restart burner properly.

Yesterday, it began "warming up" engines ;-) before tech even left driveway. I'm not going to pay third time for service call, since apparently he is unable to resolve the issue.

High speed oil burner noise compared with low speed oil burner noise

High speed oil burners noises: older traditional oil burners used on heating boilers and furnaces were driven by an electric motor spinning at 1725 rpm.

Modern "high speed" heating system oil burners usually run at 3450 rpm. The higher speed permits more air flow and greater oil burner efficiency.

But in buildings where an older low-speed oil burner is swapped out for a new "high speed" oil burner unit, the occupants are often surprised to hear that the new equipment is noticeably noisier than the old unit.

This is normal, and your heating installer would have been smart to tell you to expect this change so you don't think something's wrong with the new heating system. You're tolerating more noise for lower heating system operating costs.

George Lanthier (Fuel Oil News) reported on customer complaints about the increase in noise when new, more energy efficient but noisier oil burners are installed.

In a 2006 article in that publication he offered several suggestions of which his first is that oil companies should "scare the dickens out of the customer" meaning that the vendor should prepare the client for an increase in heating system noise level.

 

Question: oil burner rumbling noise & smoke at startup or shutdown

I changed the oil burner nozzle, now it smokes when firing;

Our oil fired furnace is smoking - do I need a repair?

Oil burner making a rumbling noise at shutdown;

Riello F3 oil burner is producing black smoke out of the chimney at startup

Whoomph sound at oil burner startup

I just changed nozzle on my furnace. I "snugged it" as instructed by tech at plumbing supply house, used metal gage to properly gap electrodes, reinstalled all and it appears to be running fine, except that a small amount of smoke is coming from the barometric damper every time the unit is in firing mode. Suggestions? - Jim 1/14/12

Just finished a boiler rebuild and heating system recommissioned and working fine. When the furnace starts the start up noise is different from the previous noise. The only way I can describe it is that the noise is more of a whoomph which stutters 3-4 times. Could that be too little air supply? I have not had the flue gases checked yet, can't get a technician with a test gauge for a few weeks yet. Any ideas? - Ian 2/11/12

My oil burner, Riello f3, fairly new, produces black smoke out the chimney on startup. It was tuned up when it was installed. However, I just noticed that the Air settings and the turbulator setting is far off from that recommended in the boiler manual for that burner and nozzle. What causes the black smoke? Is it normal? - J.L. 10/1/12

I have rumble noise on oil burner shutdown, starts and runs fine - Dennis 11/28/12

Our oil furnace is smoking do I need a repair man out to the house? - Kim 11/30/12

Reply: things to check when the oil burner smokes or is noisy at startup or shutdown

Jim:

The air suppy may not be adjusted properly;

Also, if you over-tightened the oil burner nozzle onto its mounting head you may have stripped threads between those parts. I did that (only once) and had a heck of a time figuring out what was wrong

. When you strip threads at the nozzle (typically steel, mounting in a brass nozzle line adapter) the result is oil at 100-140 psi spraying out around the leaky mount when the oil burner is running, and smoky burner operation;

if you see that problem (try starting the system briefly with ignition off so you can look for oil spray) you will have to replace the nozzle line adapter as well as nozzle.

Ian and Dennis,

Try installing a quick stop valve at the oil burner. Search inspectApedia for OIL LINE QUICK STOP VALVE to read details.

A quick stop valve makes sure that the oil supply stops cleanly when it should, which often will cure the rumbling noise you describe. If you do not fix the problem the risk is an accumulation of unburned oil in the combustion chamber (left at shutdown) that is ignited at start-up, leading to our next warning:

J.L., Ian , Dennis & Kim:

Watch out: a smoky oil burner is often headed for a very messy and potentially dangerous puffback. I suggest calling our heating service company, discuss with them what you are seeing, and schedule a service call accordingly.

 

 

On 2012-02-07 by (mod) -

Jane, it sounds as if you are describing a water heater (used to make domestic hot water for washing and bathing) - if the noise is coming from the tank it may have a problem with internal scale formation. Search InspectApedia for water heater tank scale

If the noise is coming from the oil or gas burner the system may be operating improperly, even unsafely, and you need a service call.

In the article links at RECOMMENDED ARTICLES see
NOISE CONTROL for HEATING SYSTEMS


or if it's a water heater you're asking about see
NOISES COMING FROM WATER HEATEr

On 2012-02-06 by jane

why is my tank in my loft making a rumbling noise, we have our heating and water timer to come on in the morning and we can hear this noise from the loft

 

Oil Burner Rumbling & Pulsing Diagnostic Aids


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Citations & References

In addition to any citations in the article above, a full list is available on request.

  • "Noise and Moisture, Using scare tactics” may be necessary when installing a new heating system ", George Lanthier, Fuel Oil News, M2MEDIA360, 1030 W. Higgins Road Suite 230, Park Ridge, IL 60068 847-720-5600
  • Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
  • Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
  • In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested

    CONTINUE READING or RECOMMENDED ARTICLES.

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