What is that sound from our furnace? 2

[metman]

We have a gas-fired, forced air furnace for heating our home. When we turn up the thermostat or when the temperature drops, of course the furnace comes "on."
When it comes on, there is a low frequency sound that is emitted while it begins to heat before the fan starts. I can hear this sound even without my hearing aids. Surely this is not just the sound of flames heating the plenum or whatever they are heating.

This is not a problem. I am simply curious about - what is that sound?

Design for RELIABILITY, manufacturability, and maintainability

 

[BronYrAur]

Not really the place for this kind of question, but perhaps you have a draft inducer fan or other combustion fan? That fan will come on before the furnace fires to purge the combustion chamber of any gas that may be in there. Your blower probably won't kick on until the flame has been proven by the flame sensor - maybe a minute or so after the process starts. I would not necessarily describe it as a "low frequency" sound, however.

 

[MTES93]

agreed, combustion blower or draft inducer. If getting really loud there maybe an issue w/ it. have a tech look at.

 

[metman]

Thanks for your replies. That is what I guessed.

Not really the place for this kind of question. Where would that place be?

Design for RELIABILITY, manufacturability, and maintainability

 

[BronYrAur]

I have had my hand slapped for asking homeowner questions on this forum before. It is supposed to be for "engineering" questions, not repair troubleshooting. No big deal, but I usually go to a forum called "the wall" on heatinghelp.com for that kind of question.

http://forum.heatinghelp.com/

 

[msquared48]

That's the sound of the rats waking up.

Mike McCann, PE, SE (WA)

 

[IRstuff]

People have posted homeowner questions in forum1528

TTFN
I can do absolutely anything. I'm an expert!
homework forum: //

http://www.engineering.com/AskForum/aff/32.aspx

faq731-376 forum1529

 

[metman]

two lps. I did not know about those forums - thank you.

in-noc-u-ous

[ih-nok-yoo-uh s]

adjective

1. not harmful or injurious; harmless:
an innocuous home remedy.

2. not likely to irritate or offend; inoffensive; an innocuous remark.

3. not interesting, stimulating, or significant; pallid; insipid:

I suppose even though it is intended as 1 or 2, some people take it as 3 since 1 includes the horrid "home remedy" clause.

I have answered a few dumb or silly questions on tips so maybe I can be forgiven one more time.

In any event, now I know where to go for these kind of questions.

Design for RELIABILITY, manufacturability, and maintainability

 

[LittleInch]

Well it might be a problem unless it's always been there. Rumbling can be a blocked nozzle such that the burner isn't fully igniting or even a faulty solenoid valve which is chattering away and is then masked by the fan noise.

If you can see that the flame is good and steady all over the burner then fine, but worth looking to see what you can see.

Fan noise is still the best guess, but it shouldn't be that loud IMO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[urgross]

Could be an electric damper actuator. It would need to make end prior to fan actuating.