Resolved > New Water Heater "Hums" When It Turns On

[Twowaxhack]

There is a baffle that runs through the center of most gas fired natural vent heaters and sometimes they can vibrate. It is under the flue cap on top of the heater.

This Answer is the correct one.

 

[Twowaxhack]

The heater is just a standard heater without any motors. The frequency of the hum is like that from a 2-foot pipe (like a flute). It builds up a couple of seconds after the burner ignites and dies out about 5-6 seconds after that.

Your heater may very well be a standard AO smith heater but the one in the video you just posted is not a basic water heater.,, that’s a low-nox heater and has a special burner in it. It’s more energy efficient.

So if that’s the heater you have, it’s not just a normal water heater.

The hum you describe also happens on other brands of heaters.,,,.Rheem does it too., it’s the air pressure change from the burner coming on vibrating the flue baffle and burner chamber pan.

 

[skeezix]

UPDATE:

The previous things that I did did not fix the humming problem. After replacing the expansion tank I thought the problem was gone but a few days later it came back.

So I removed the burner assembly and then I could remove the little piece of copper pipe. I could also see where the little piece of pipe had been resting on the burner. The screen covering the top of the burner was somewhat dented.

Anyhow, I didn't do anything other than carefully reinstall the burner about a month ago and the hum has not returned.