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Oil burner schematic (C) Carson Dunlop AssociatesElectric Motor Noise Diagnosis & Cure

Causes of noisy electric motors used on HVAC equipment, oil burners, air conditioners, fans, water pumps, appliances, etc.

Electric motor motor noise diagnosis: this article describes the causes, diagnosis, cure & prevention of noises traced to the electric motor component of an oil burner, air conditioner, or other electric-motor driven equipment.

The sketch of an oil burner shown above is provided courtesy of Carson Dunlop Associates, a Toronto home inspection, education & report writing tool company [ carsondunlop.com ].

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Troubleshoot & Repair a Noisy Electric Motor

Table C: 7 Things to Check if an Electric Motor is Noisy
1. Motor won't start, hums If the motor is humming it is probably not running.

Watch out: if an electric motor hums and won't start, turn it off immediately to avoid further damage or unsafe conditions.

See Table A in

ELECTRIC MOTOR DIAGNOSTIC GUIDE.

Often the problem is a bad start capacitor.

See CAPACITORS for HARD STARTING MOTORS )

Also check the motor temperature and current draw.

If the electric motor won't start and is is silent ,

see ELECTRIC MOTOR OVERLOAD RESET

For HVAC compressor motors that hum

see HUMMING MOTOR SOUNDS from A/C or Heat Pump system
2. Motor shaft end play Excessive electric motor noise can be caused by excessive motor shaft end play - the distance the shaft can move in and out of the motor.

Beckett (1989) [1] notes that a new electric AC motor will have no more than .035" of movement in and out. Push the shaft all the way "in", and measure its outwards movement. (Automotive feeler gauges can sometimes assist).

If electric motor shaft end play is more than .060" and if noise is a problem, the motor could be suspect.
3. Motor is improperly mounted or aligned

Motor vibration noise can be caused by misalignment of the motor due to its mounting position or due to bad shaft couplings to driven devices such as fans or fuel units.

We find this problem also on hot water heating circulator motors.

Realign the motor or replace a bad coupling. - Beckett (1989) [1]
4. Electrical phase problems If the motor is a 3-phase unit running only on one phase there may be an open circuit, blown fuse/tripped breaker, or unbalanced voltages. Any of these conditions can cause motor vibration.

Check for open circuit, blown fuse, tripped breaker, uneven voltages on the three phases. - Beckett (1989) [1]

DMM DIGITAL MULTIMETER HOW TO USE
5. High or unbalanced voltages Any of these conditions can cause electric motor vibration and noise

Check wiring connections, transformer, voltages - Beckett (1989) [1]

DMM DIGITAL MULTIMETER HOW TO USE
6. Bad electric motor bearings Bad motor bearings cause vibration at the shaft support at either end of the motor.

Check for bearing damage (loose, side play, noise, visible damage); Usually motor bearing damage is caused by improper mounting or motor misalignment.

We've seen a whole series of hot water heating system circulator motors that were destroyed and replaced, one after another until finally a more experienced tech noted that the motor mount was askew. Beckett (1989) [1]

It's probably too late but take a look

at ELECTRIC MOTOR LUBRICATION
7. Loose coupling between electric motor and driven appliance A bad coupling between the motor drive shaft and the driven fan, fuel unit, or other component can cause vibration and noise as well as motor damage. Replace the bad coupling; If there is a loose sheave, tighten the set screws or replace that component.

Notes to the table above

Adapted & expanded from Beckett (1989)[1]

Other Noises at HVAC Equipment

Watch out: some noises at HVAC equipment could be a sign of dangerous operation. For example, rumbling, stumbling noisy oil burners, especially accompanied by smoke, or oil smells, could be a sign of

pending PUFFBACKS, OIL BURNER.

Squealing motors may be traced to failed bearings, overheating, and on occasion the risk of an electrical fire.

...


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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

On 2019-05-04 by (mod) - a loud motor makes a steady blasting sound

Beth

In my view you're on the right track to find the motor noise sound by noticing the time of occurrence and frequency; now what's needed is to look for mechanical equipment or motor that is operating near where you're hearing the noise;

If you think it's an electric motor the super may help by turning off equipment or circuits selectively.

On 2019-05-04 by Beth

Every day - from approx 5pm to 8am, a loud motor makes a steady blasting sound for approx 6 minutes; the cycle repeats every 15-20 minutes. My super does not know the source.

I can hear the sounds constanty in the stop/start cycle manner. The sound is consistent and steady and LOUD. Even with windows CLOSED i can hear it. Any ideas on how to identify source? Thsnl you!

On 2019-02-21 by (mod) - motor that has a 100 dba electrical scream noise

Done,

Most often that screaming sound as from a failing bearing which may in turn be due to a lubrication failing or something else.

It would make sense to check the motor shaft end play and bearing for wear. It may be that nobody wants to fool with the motor to do that but you might warn that the screaming is likely to lead to a total failure as well as of course the risks that can come from overheating.

On 2019-02-21 by Don Rigdon

DVance2011@gmail.com

We have a very large pump motor that has a 100 dba electrical scream noise at my work, i have a mp3 recording that I can send if you respond to my email

The techs here at work say they do not know what is wrong with it. I am looking for suggestions as I am very tired of hearing it all day.

Thanks

On 2018-12-06 by (mod) - motor emits a low howl

Are we discussing the refrigerator or an air conditioner.

If you use the search box at the top or bottom of any of these Pages you can find our article on air conditioning howling noises. There you will find a list of common causes.

On 2018-12-05 by Andrew

My new Samsung fridge twin air runs for two hours at each cycle but it emits a low howl, which is very annoying.

On 2018-08-21 by (mod) - steam trap operating noise

Brad

Thank you for your helpful comment

On 2018-08-21 by Brad Lehmann

@Arthur,
That sure sounds like a steam trap operating to me. Like an Armstrong inverted bucket steam trap that fills with condensate which lifts a float which in turn opens a valve to allow the condensate to be pushed back to a feedwater tank or boiler

On 2018-03-04 by Rhian

I have an electric water pump which is in a shed. Since this cold weather I haven't had any water since Thursday morning. I've tried a hairdryer on the pipes to no avail. The failure light is on.

Something must have kicked in last night as the toilet cistern filled up but now nothing.
I've tried the reset button and the pump makes a whining noise but nothing happens? Help!

On 2017-12-14 by (mod) -

Arthur, adding

See HEATING SYSTEM NOISE DIAGNOSIS https://inspectapedia.com/heat/Heating_Noise_Diagnosis.php

or our full catalog of heating system noise & sound causes & cures.

On 2017-12-14 by (mod) - sneezing noise from heating system

Arthur,

1. Air noises: I infer from your question that there may be air trapped in the system. Such air, essentially a hydronic heating system that is not completely filled with water, can cause sounds like water gushing through pipes, also bubbling and gurgling.

It's also possible that during boiler re-fill, instead of removing previous trapped air, we are left with new, worse air trapped in the system.

Just what sort of noise air makes in a hot water heating system will depend on the orifices through which it is being forced. I speculate that that can create a wide range of sounds, not all of which would be polite to describe.

There may be two other sounds from your system that bear thought

2. Vibration noises, for example transmission of normal vibration from an oil burner motor through oil piping or other metal parts into the building structure or piping.

3. Creaks and clanks can occur where pipes move through walls and floors as they expand and contract during heating system operation.

4. A "sneezing noise" could be a valve or vent opening or operating normally

All of these sounds can be fixed.

I'm not sure why you drained the system in the first place. Saying "there's not much air in the pipes" is like saying "our cat is only a little-bit pregnant".

That's not the best analogy since even if there were only a little air that was observed, there could have been a greater amount of air that the plumber didn't find and thus didn't observe.

In any case, draining (and presumably re-filling) the boiler with water is not a repair for noises. And for hot water heat there are some small disadvantages in doing so (increasing the level of minerals in the system, for example).

That suggests that maybe your plumber was not an expert on hydronic heating and air purging.

She should have

- discussed the sounds and where they were heard

- inspected for the location and operating condition of air bleeders throughout the system, making sure they're properly located and working

- tried opening manually operated air bleeders

- if that didn't work, tried one of the methods we describe in our AIR-BOUND HEATING SYSTEMS article series to force air out of the system.

https://inspectapedia.com/heat/Air_Bound_Heating_System.php

On 2017-12-14 by Arthur

I have been eagerly reading your contents regarding noises in a heating system. If the answer is within, I have not found it yet. Hopefully you can help.

We have a gas fired boiler with baseboard heaters. Relatively small house, it's a 3 bedroom cape built around 1920-1940, and the boiler was replaced just before we moved in...2013. It's a Burnham hydronics series 2, 80.1% efficiency, which is at the very low end of the spectrum. I started by having a plumber drain the system, there are three zones.

He flushed each one as I looked on trying to learn how to do it. When he was done, he said there wasn't much air in the pipes at all. And of course, it did not make a difference with the noises we experience.

The three zones appear to be

1. two bedrooms and bath upstairs;

2. front half of first floor, living room and dining room;

3. rear half of first floor, kitchen, bath and rear bedroom/den;

The noises range from loud gushing of water through the pipes! Not just trickling, gurgling or bubbling/burbling. Almost sounds like someone is squeezing a large diaphragm/container of water though the pipes, then a little less noise while the diaphragm/container refills and gets squeezed again...over and over.

Another noise sounds like metal on metal clanking, and it seems to be coming from the boiler room itself...i.e. not in the baseboard radiators throughout the house. I've tried to run downstairs to see if I could see exactly where the noise is coming from, and I just can't seem to isolate it!

I've checked to make sure all the exposed copper pipes running horizontally in the basement are secured and not loosely hung.

Other times it’s a loud vibration noise that softly rumbles the house. If I can explain it better by sending or attaching pics, let me know.

Thanks in advance. PS my plumber said he would have to be here to hear the noises to offer any other real help…since we don’t know when the noises will happen, and they don’t happen all day long, it doesn’t make sense to pay him hourly to sit around and wait for the noise to happen…or does it?


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