[Resolved] Strange Humming Right After Heater Burner Ignites

[Skeezix]

Ever since I replaced my old water heater with a new AO Smith 40-gallon gas heater something makes a strange hum right about 5 to 10 seconds after the burner ignites. The hum is around 256 Hertz and does not vary in pitch. It increases in volume for 1 to 2 seconds, then tapers off and is gone after 6-8 seconds. I can hear it through the adjoining wall and also very slightly through the ceiling. The hum never occurs except very soon after the burner turns on. I don't think it occurs when the burner turns on during water usage but I don't know.

Any ideas what could be causing it, and do I have to worry about it? It's been going on since February when I installed the water heater.

 

[Phog]

There have been others asking similar questions on these forums in the past -- not exactly what you are experiencing, but other strange things that are not easily explained -- clicks, whooshes, groans. The short answer to your question is that it's not something to worry about unless you're seeing some other symptom of a problem. The longer answer is that it's probably either normal behavior for your particular model, or else something related to thermal expansion and/or an internal part very slightly out-of-tolerance. Could it be a warning sign that you have a burner assembly that will need to be replaced in 8 years instead of 15+ years, or a slight defect in the tank that will someday become a leak? Sure. But much more likely it's just an idiosyncratic thing that will make no difference in the function or longevity. As long as the unit is installed correctly, with properly sized exhaust ducting, gas line etc, and presently appears to be working correctly, my own opinion is to not worry about it at all.

 

[Sponsor]

 

[Skeezix]

No other problems noted with the heater or its installation. Guess I'll just have to wonder about the hum for the next 12 years.

 

[Jeff H Young]

sounds like the gas flowing . record noise for warranty purposes , they might change gas valve out to solve issue. contact manufacture. that said they may claim its a normal sound and its possible that it is normal. but its bugging you so thats the possible cource of action I belive.

 

[Fitter30]

Didn't say if it was nat or lp gas. Lp has more problems with humming. Humming can be caused by gas pressure at the burner or the air shutter. Just move the air shutter just a little mark where it is now with a pencil.