Annoying noise

[aj]

I have a problem, and am wondering if anyone can give me some ideas as to what the cause may be. Every time the furnace is turned on, after the house heats up to approx. room temperature, there is an annoying whining sound that appears. There is a built in humidifier that is hooked directly up to the water supply in the house, and from what i can tell, it sounds like the noise is coming from there, but i'm not sure. Any info about this problem or how it can be fixed will be greatly appreciated!!!

Thanks

[Hube]

You could be hearing a "bad" bearing noise in the fan/or motor. Sometimes it takes a few miutes of running before it "whines... It's a long shot, but worth checking out by running ONLY the fan manually. et us know how you make out, and see what else we can come up with. Hube

[aj]

thanks for the suggestion Hube...tried it and there is no noise...it seems to only come when the heat is on and goes away after the heat is turned off. The noise that we are getting is not all the time...it is intermittant, usually about every 3 minutes or so and lasts for about a minute or two--but only when the heat is on. Any other suggestions???

[Hube]

You say it "only come when the heat is on and goes away when the heat is off" When you say "Heat", do you meaning the burner ONLY?, or when BOTH the burner AND fan are on? Is this a DRUM type humidifier? Try turning the humidistat down and check if noise is still there. Turn the small water valve off to the humidifier line and listen for the noise. I assume this is a plenum and ducted furnace, are you hearing a heat noise on duct (metal) expansion?or a loose damper further down the line? Also, check for any loose parts around the fan and humidifier. Hube

[aj]

Thanks again Hube. Yes, it is a drum type humidifier and as u suggested I turned off the water valve that supplies the humidifier and the noise has yet to reappear. I think it's safe to say problem solved.