Buzzing aquastat relay © D Friedman at Heating System Buzzing Noise
Diagnose & cure buzzing & vibration noises

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Diagnose & fix buzzing or vibration noises at heating equipment:

What are the causes of buzzing or vibration noises at heating equipment like boilers, furnaces, or water heaters? How is buzzing noise found and fixed?

This noise control article series discusses the diagnosis and cure of heating system noises, including heating equipment noise, heat piping or ductwork noises, radiator noises, steam pipe banging, and steam radiator vent noise control. We describe just about every single noise that might come from or have to do with building heating systems.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Heating System Buzzing or Vibration Noise Diagnosis & Cure

Buzzing aquastat relay © D Friedman at Watch out: while adding sound control barriers and insulation around a mechanical room be sure that you do not interfere with proper combustion air supply or you risk making the heating system work poorly or you may make it unsafe, risking carbon monoxide production and even death.

Buzzing sounds and vibration at oil or gas fired heating boilers, furnaces or water heaters can be caused by a variety of problems such as a control cover touching a relay switch, control unit transformer failures, bad motor bearings, or loose mounting hardware.

Buzzing and similar vibration sounds may also be traced to fuel oil piping that is not properly mounted, is in contact with building surfaces, and is transmitting vibrations from the heating appliance or oil burner to the building.

If an electric motor is vibrating, normally or because of wearing bearings, its vibration is easily picked up, transmitted, even amplified by metal parts like ductwork or fuel piping.

We might also trace buzzing sounds to a failing low voltage transformer such as the transformer that may power zone valves, thermostats, and some other heating system components. [Blue arrow in my photo]

Buzzing heating system control relay switches also can be quite noisy. our photo illustrates how a trapped aquastat relay buzzing problem can happen. Our measuring tape is stretched across the two steel ends of the aquastat control.

The red arrow in the top center of our photo points to a relay in this control.

The edge of my yellow measuring tape that is closest to the top of the relay is also tight against the steel ends of the box that contains this whole control.

When the control box cover is installed, from the location of the edge of my tape right above the relay top, you can see that there will be very little clearance between the relay's moving head and the an aquastat control cover that is pressed tightly in place.

Question: the oil burner rumble, vibrated, & the house smelled like truck exhaust

(Sept 29, 2017) Jessica said:

Had the Miller oil furnace tuned up. The tech replaced some parts and the furnace seemed to be working fine when he left.

A week later I turned it on for the first time, it rumbled a bit loudly, vibrated more than usual, the house smelled like truck exhaust, and then it switched off, I believe from overheating because the panel door was very warm for the short time the furnace was on. Naturally this happened at 6 p.m. on Friday.

The windows are all open now for fumes. Any ideas?


It sounds to me as if the oil burner is not operating properly. You did the right thing to turn it off and leave it off. It's time to call your service technician to ask him or her to return to correct the problem. There are many possible causes, of which a few examples include an air leak in the oil piping, or an incorrectly installed nozzle, or combustion air problem.

Below we continue with a catalog of sources of oil burner buzzing or vibration sounds.

Heating Control Device or Relay Noise Buzzing Details

If the control cover is lightly touching the relay switch the control may simply buzz when the relay is trying to move.

On some controls this clearance is so tight that the relay or is trapped solid so that it cannot move - leading to a no-heat service call.

So if you notice that the control cover on your aquastat (or on a cad cell or stack relay) has been bent slightly convex, or has been left slightly ajar (our photo, above right) think twice before jamming it on tightly. Thanks to oil heat service technician Bob at Bottini Oil for this service tip.[3]

Heating Equipment Buzzing Noise from Gas Burning Equipment, LPG or Natural Gas

Heating Equipment Buzzing or Vibration Noise From Oil Burners

Common sources of vibration or sources of buzzing vibrating sounds in or close to an oil burner include:

Heating Equipment Buzz or Vibration Noise Transmission via Ductwork or Heating Oil Fuel Lines

First try simply pressing on a suspect oil line to an oil burner or on ductwork near the air handler of a furnace. If the buzzing or vibrating noise diminishes or stops you are probably close to the noise source.

A heating oil fuel line fastened to the underside of floor joists over a basement and using simple metal strapping might be using the whole floor structure as a speaker amplifier.

Sometimes we use a mechanic's stethoscope to try to isolate noise right to a specific component. That makes sense if the buzzing or vibration is so horrible that we think there is a component that's failing: replace it before you suffer loss of heat, loss of hot water, loss of air conditioning, etc.

But normal vibration can also be noisy if transmitted to pipes or ductwork.

We can often correct that problem by using noise isolating fasteners to secure fuel oil piping or for duct vibration we might simply tape loose duct parts with adhesive foil tape.

See OIL LINE BUZZ & VIBRATION CURE for details about buzzing and vibration from oil heating equipment oil lines & piping.

Also see OIL TANK PIPING & PIPING DEFECTS if the noise is coming from or being transmitted by fuel oil piping

See AIR HANDLER / BLOWER NOISES for a discussion of noisy furnace or air conditioner air handlers or ductwork noises such as air leaks, clicking, thumping or banging duct noises, fan noises and vibration dampener noises or rattling at fan motors

See DUCT SYSTEM NOISES rattling & buzzing from loose components, if the noise is coming from or being transmitted by ductwork.

Watch out: Buzzing, snapping, crackling, popping - may be dangerous electrical switch or breaker indicators. Buzzing also occurs at failing or failed relays such as the relay in a heating system aquastat or circulator controller or in relays used to control HVAC fans, blowers, and compressor motors.

Buzzing noises from HVAC equipment like air conditioners, heat pumps, heaters are described further at BUZZING SOUNDS sounds from A/C, heat pump or inverter or from other equipment in, or, or near buildings

Buzzing noises from water heaters are also discussed at NOISE, WATER HEATER

Curing or controlling noises traced to building heating systems is divided naturally into two topics that should to be addressed in this order

  1. Identify the source and cause of noises traced to the heating system or its components. Some heating system noises are normal and are thus not a worry.

    But other heating system noises (rumbling, buzzing, banging) might be a sign that the heating system needs repairs, that it is not operating efficiently (costing more than necessary for heat), or the heating system may be unsafe.

    To rule out heating system operating problems, review the Heating System Noise Cause Diagnosis Articles we list just below in this document.
  2. Isolate heating system noises, or prevent heating system noise transmission through the building. Once we are confident that the heating system noises themselves are normal, we can focus on keeping those noises out of the rest of the building. You will still need to identify specific heating system noise sources, since some noise control steps focus on specific heating system installation details.

    Once those noise and sound problems have been addressed, normal building noise transmission and sound control measures, such as sound insulation, can be applied to the room where heating equipment is located.


Buzzing Oil Burner Question: Oil Burner Noise: loud buzzing, vibrating sounds

I have a riello oil burner which makes a steady noise on and off when heating is on but all of a sudden the steady noise is much louder like a loud buzzing/vibrating noise...any ideas what it could be ? - Kerry

(Dec 24, 2012) Fred said:

My Aero burner was burning loud, with a lot of flapping on the chimney air valve, furnace was stored for 6 years before I installed it in my garage. I took the nozzle and electrodes out, cleaned them up and reassembled the gun with the electrodes exactly the way they were.

I primed the pump and re-connected the wires properly, but the furnace does not fire now. It runs for a minute, then shuts off and turns the red light on. I can use a little help here

Reply: check these things:


Provided that you can rule out oil burner noise caused by a dirty or misadjusted flame and actual burner operation, there are several common sources of mechanical noises in oil burners too.

This is a good application for an inexpensive mechanic's stethoscope. That device includes on the sensing end a metal rod whose end you can touch to different parts of a motor or assembly to see where vibration is loudest.

Common sources of vibration or sources of buzzing vibrating sounds in or close to an oil burner include:

Let us know what you find, what we learn will help others.

For buzzing traced to an oil line or transmitted by the oil piping, see OIL LINE BUZZ & VIBRATION CURE

Question: Grant 50/90 heating boiler ran out of oil, trouble getting started, now buzzing, won't fire

hi i have a similar issue to clark as above i have a grant 50/90 boiler which ran out of oil and was filled and bled as normal it took a while to start but was running for 20mins then cut out

i went to press the red reset button and it started making a buzzing noise and now will not fire on its own

i have to press the reset button 30-40 times it will fire for another 20 minutes as normal but cuts out again any ideas on whet i have to replace or check? thanks - Clinton 2/5/12



I can only guess from your note, but if a heating system runs out of oil, it's common to have to bleed air from the oil lines and filter and oil pump unit to get it working properly again. If the air-bleed-out was incomplete you may continue to have operating problems.

A second problem is that often when your system draws that last bit of oil from the tank it may suck along sludge and crud that then clog up the oil filter or nozzle. Sounds as if you need a service call. Be sure to tell the tech you had just run out of oil before these problems began.

Watch out: do not keep pressing the reset button when an oil fired heater is going off on safety-reset. Doing so risks causing dangerous PUFFBACKS, OIL BURNER

Question: random loud oil burner noise - pipes vibrating

(Jan 7, 2015) Ellen Bowser said:
Since replacing our old hot water furnace with a new one we have had a noise problem and had the men back several times.

Randomly, several times a day a very loud noise followed by the pipes vibrating when furnace starts up. Shakes the whole house. Drained the line,s change the flow and replaced flaps to allow a slower flow of water. This is so loud it wakes everyone up with a startle.



We need to inspect the equipment closely before and at the start of this noise complaint, using if necessary a mechanic's stethoscope if the sound source is not obvious. Noisy burners or chimneys can be quite dangerous; or the noise could be a circulator or even loose piping.

See HEATING SYSTEM BUZZING NOISE and see OIL LINE BUZZ & VIBRATION CURE when the oil burner noise is traced to or is transmitted by oil lines & pipes

Question: How to find the source of buzzing vibration noise near the chimney when furnace operates

I came upon your website and typed in a question but I don't know how to do these things; I couldn't tell where/how to get the answer. I found this e-mail address to try and hope someone will get this.
I am an old lady living alone, so contractors take advantage. This past winter the furnace made loud buzzing/vibrating noises when firing.

The service person said it was air in the pipes, which it wasn't. I called another after everyone said he was full of it. The next company owner said my firebox hadn't been cleaned out properly for years and was falling apart.

The noise was due to all the ash and the change in loudness (louder the lower the outdoor temp got) was due to the air density changing with the cold. He said the firebox was so plugged up that it couldn't get enough air. The furnace was about 30 yrs old, so I thought that a new part sounded reasonable.

As the weather got warmer, it no longer made the noise. But I had the new heating coil & firebox installed. It started making the same type of noise again sometimes when the furnace fired, not as loud as last winter, but getting louder now. Of course when the guy came back to look it didn't make the noise.

The noise (previously and now) is not audible when standing next to the furnace. You hear it when you walk far enough away from the furnace parallel to the chimney. On the first floor, the noise reverberates all over. There are 2 fireplaces and it seems like the noise vibrates out from them.

Now the guy says this reverberating noise can be cured by inserting something (snake?) into the oil line. He claims the oil line makes a pneumonic vibration. I have looked at numerous websites and see nothing like this. All claim that the kind of noise I have is bad or loose bolts, motor blower, etc.

No one mentions an oil line causing a noise. I would greatly appreciate an unbiased opinion of this situation. - Anonymous by private email 2017/09/09

Reply: safety checks first: check the chimney and furnace area for signs of a fire or dangerous smoke

When a furnace makes loud buzzing/vibrating noises when firing I would look for things in order of safety first.

That's why I said to look at and smell around your heating system. If you see fire or smoke turn the system off and call 911.

If the noise is actually in the chimney that could indicate a burner that is not operating properly - and is unsafe.

I an extreme case a noise in a chimney could be a chimney fire: you'd know this (and run the hell outside and get away from the house and call 911 fire department) if you heard a roaring in the chimney and saw smoke pouring out of the chimney top.

Otherwise we're looking for an experienced service tech who can think clearly. I'll suggest some more possibilities below that might help you interpret what you're told and also to ask some questions.

Ultimately you want to say to the technician: ok so SHOW me the part that is causing the trouble and explain to me in plain english why it's doing that.

Key Step: Ask for a Senior Service Technician

call your heating service company. Talk politely and without sounding like you're making trouble, to the service manager. Say Look, we've had repeated service calls, my system isn't working right and it might be unsafe. Please find your senior, experienced, sharp service technician and ask him or her to come over here and help sort this out.

More opinion about trouble tracking down the buzzing vibration sound

I don't assume that the heating guys who disappointed you are necessarily crooks. More often they're either incompletely trained or they know stuff but were not English majors in school.

First: what do you have? "Furnace" means forced hot air heat. "Boiler" means forced hot water or steam heat. Calling equipment by the right name cuts back on the nonsense the techs might try to tell you.

Also an air heat system has different parts so we'd look in different areas for noises than at a boiler.

A dirty or poorly-cleaned or poorly-adjusted system might rumble or roar or smoke but buzzing usually is traced to

Vibration can be picked up in sheet metal (ductwork of an air system) or water pipes (in a hot water heating system) or in the fuel line if it's an oil fired burner at a boiler or furnace.

Sometimes by pressing on a suspect pipe or oil line the noise will change or stop - that's also diagnostic.

See OIL LINE BUZZ & VIBRATION CURE for a discussion of the causes and cures for buzzing and vibration that seems to come from the oil piping itself.

Now: vibration might be "normal" - all motors vibrate a little bit.

Or it might mean that a motor bearing or part is wearing out.

If the noise is "normal" it might still be "loud" if the vibration is being picked up by piping, tubing, ductwork that conduct noise and even amplify it in a building.

Let me know what you're told next and perhaps I can suggest some follow-up questions.


Continue reading at OIL LINE BUZZ & VIBRATION CURE, or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


Or see BUZZING SOUNDS sounds from A/C, heat pump or inverter or from other equipment in, or, or near buildings


Or see HEATING NOISE DIAGNOSIS FAQs - Q&A's posted originally to this article

Or see NOISE, WATER HEATER - more buzzing or other noises

Or see WATER PUMP PRESSURE SWITCH NOISES - other buzzing and vibration noises

Or see these

Heating System Noise Diagnosis Articles

Suggested citation for this web page

HEATING SYSTEM BUZZING NOISE at - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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