Totally Random "HUM"

Boring

Sounds like wind blowing across a tv antenna making a hum sound that lasts for 3 to 5 seconds....Originally thought it was coming from the new ac unit outside...but ruled that out as I heard the sound and there was no wind...heard it once outside and thought it might be coming from the neighbors outdoor hot tub... Think it might be coming from the boiler room...but can't figure out what to look for...thinking it could be coming from a diaphragm in something, but it is so random and doesn't seem to be associated with a normal boiler cycle...I'm stumped... could it be an expansion tank, or air bleeder,

kcopp

Whats the boiler?

Boring

Knight KBN 80 with indirect HW and radiant floors...

Jamie Hall

That sort of noise can be really hard to pin down. If it really seems sort of like wind on a TV antenna (do people still have those???) it probably is air vibrating something -- but what. It could be related to the intake or exhaust of the boiler. It could also possibly be related to something quite different -- even something as silly as a loose bit of siding, or a shingle.

It could be the new AC unit -- if you hear it when the unit's outside fan is running, and never when it's not.

It could also --though less likely -- be something related to a pump on your system, although that would in most cases be somewhat more regular -- it would come and go in a more predictable pattern, simply because the driver was regular.

All of which isn't much help.

STEVEusaPA

It’s cold out…maybe low gas pressure?

EBEBRATT-Ed

do you have csst gas pipe hooked to the boiler?

Boring

Well, the antenna....we still have one and grab signals out of the air...works good....Can't justify the cost for cable....

No csst gas pipe...it's all black pipe from the meter....

Thanks for the replies...have to keep my ears sharp....and get lucky

Boring

Holy Moley....I called it a "random HUM", but I see on another post that a hum is also referred to as a "HOWL"........ My Knight KBN 80 was installed in 2007 and has never made any unusual noise until this heating season...it's been very random, but as indicated by others, when it Howls it can be mild to rattling the house. Weeks can pass with no noise, but then it starts up again maybe a couple times a day, but never long enough to pin point and to sit and wait for it to happen is impossible... Where do I start?

kcopp

When was the last time it was pulled apart, cleaned, serviced and had a combustion test?

Boring

Cleaned and serviced annually...don't think there has been a combustion ever unless they did that when the main board was replaced a couple years ago....

Jamie Hall

Boring said:

Holy Moley....I called it a "random HUM", but I see on another post that a hum is also referred to as a "HOWL"........ My Knight KBN 80 was installed in 2007 and has never made any unusual noise until this heating season...it's been very random, but as indicated by others, when it Howls it can be mild to rattling the house. Weeks can pass with no noise, but then it starts up again maybe a couple times a day, but never long enough to pin point and to sit and wait for it to happen is impossible... Where do I start?

If it really is a howl from time to time, but quite erratic, another place to look is a failing fan bearing.

kcopp

It needs to have a combustion test run on it. Especially w/ LP its out of tune.

EdTheHeaterMan

Boring said:

Holy Moley....I called it a "random HUM", but I see on another post that a hum is also referred to as a "HOWL"... ... Where do I start?

This can be very important to determine whether it is a HUM or a HOWL

The HUM is usually because you forgot the words, and is a perfectly acceptable way to continue until you get to the part you remember the words.

On the other hand the HOWL is limited to only on song I can think of, https://www.youtube.com/watch?v=_FA85RO89HA
Little Red Riding Hood by Sam the Sham and the Pharaohs.

I Hope this clears up any misunderstanding.

Boring

Cleaver