Boiler humming

[Bd19]

Hi I have a Well McLain oil boiler (maybe 15 years old, serviced annually) that functions correctly, but a loud humming can be heard through the whole house that won’t start until maybe 20 or seconds after the burner fires up and will continue for another minute or two after the burner stops. Noise is unrelated to any of the circulating pumps. The humming will fairly slowly drop in frequency and volume as it dissipates. It is clearly transmitted through the pipes.

I had a tech under a service contract come look at it and said he didn’t know what the cause was but the boiler was operating fine and the noise although loud was nothing to be overly concerned about.

The noise is fairly obnoxious, I was hoping someone may have advice on where to start troubleshooting.

Thanks

 

[Fitter30]

Not knowing what burner you have most burners go thru a prepurge before firing and possibility of a post purge. Might have something to do with the pressure regulator in pump or motor bearings. With burner running and with a long screwdriver put your ear to the handle and the tip to different parts of the burner like a stethoscope.

 

[Sponsor]

 

[Bd19]

Not knowing what burner you have most burners go thru a prepurge before firing and possibility of a post purge. Might have something to do with the pressure regulator in pump or motor bearings. With burner running and with a long screwdriver put your ear to the handle and the tip to different parts of the burner like a stethoscope.

Thank you, it’s a Beckett 21805. I listened with a screwdriver, but hard to tell the origination point. Will need to keep trying things.

 

[Skeezix]

Similar problem here.
In February 2020 I replaced my gas water heater with a new one. Also installed a new gas feed line and shutoff valve. Since then, whenever the burner turns on, the water heater hums (not too loudly) for about 5 seconds, then the hum tapers off. No idea what's causing it. Not really a problem... right now. Would be interested to know what you find.

 

[Fitter30]

Similar problem here.
In February 2020 I replaced my gas water heater with a new one. Also installed a new gas feed line and shutoff valve. Since then, whenever the burner turns on, the water heater hums (not too loudly) for about 5 seconds, then the hum tapers off. No idea what's causing it. Not really a problem... right now. Would be interested to know what you find.[/QUOTE
Burning lp or natural gas?

 

[BillTheEngineer]

If nothing has changed with your system, I would suspect it's a circulator. I know you said they service tech said everything was fine. Do you have more than one circulator? Does it happen only when one zone calls for heat?

There are only a few reasons for sound to be coming from a hot water heating system. Water boiling in the boiler, circulator or zone valve. Or something else in the home making the noise and it's being magnified thought the heat system (Not a likely reason).

I say circulator because it can still to what it needs to do and the bearings in it are shot. Maybe part of the impeller came off and it's out of balance.

Water boiling in the boiler (kettling) can also make noises. For that to happen there would need to a spot with poor flow in the heat exchanger (partially blocked, it's a closed system unless there is a leak it's constantly being refilled, not to likely do get a blockage). Poor flow because of the bad circulator or zone valve usually won't do it and you will just have a cold home. The heat exchange can get dirty on the flame side if the boiler is not set correctly (running rich) or the flue liner is failing and falling off and down on to the heat exchanger.

 

[mgmachine]

Thank you, it’s a Beckett 21805. I listened with a screwdriver, but hard to tell the origination point. Will need to keep trying things.

My Beckett 21805 motor is starting to hum as well. Also it is very hot to the touch after it runs 15 minutes. I ordered a newly revised 21805u motor.

 

[Skeezix]

UPDATE TO MY PREVIOUS POST:

I removed and replaced the burner in my NG heater and the humming problem went away. The R&R process took me about half an hour. No special tools required.