What causes 60 cycle hum?

[bjaspud]

I just finished installing my Reznor 45,000 btu force air gas garage heater in the garage of my new (to me) home and it has a pretty pronounced '60 cycle hum' to it.

The furnace in the home also does the exact same thing.

I read somewhere that the hum is coming from the 24v supply.

Can anyone tell me what causes both the furnace and the heater to give off such a loud electrical hum?

The noise is constant, neither unit is operating. They both just sit there and hum. You can hear the sound from at least 5 foot away.

The furnace in my current home is silent in comparison.

Is there any 'fix' for the noise?

Thanks,
Spud

 

[Charles (in GA)]

Its the transformer vibrating. It may need to be remounted differently, possibly on shockmounts or in some way that the natural vibration of the transformer will not pass thru to the metal of the heater, which is what is causing the hum. The lower the frequency the more pronounced the hum. I have a bathroom light dimmer which uses a frequency chopping electronics to dim the light, and with the lights dimmed, I can hear them "singing" as the filiments vibrate.

Charles

 

[tdkkart]

Sometimes you can quiet them down by wrapping a rubber band around the transformer.

 

[nehog]

One trick is to take some epoxy (rated for 200 degrees, most is) and coat the transformer. Best is to 'dip' the transformer if you can. Of course protect the terminals so you can reconnect it.

 

[bjaspud]

Is there anything that make the hum more pronounced? Voltage higher or lower than normal. Insufficient ground?

 

[BillK]

Spud,
My Carrier furnace in the house did the same thing when we installed it about 10 years ago. All I did was make a plate out of 1/8" steel to put behind the transformer to stiffen the sheet metal up and you can't hear it now. The reason you hear it is because the flimsy sheet metal it is mounted to is acting like a big sounding board. If you took it off the sheet metal, you would never hear it. I would try rubber mounts first, that is the easiest fix.

 

[foolishpride]

It's probably the core laminations vibrating against each other. I've heard large dry type transformers (1500 KVA) and small ones do it. Some were so loud you couldn't hear yourself think. They've always tested fine electrically though.