Yesterday I installed 3 Marley electric baseboard resistance heaters in my finished basement: a 2500 watt, 1000 watt and a 750 watt unit. All are 240V running off one 30 amp double pole circuit breaker with 10 gage copper wire. Each heater has it own thermostat. The 1000 and 750 watt units have bi-metallic manual thermostats, and the 2500 watt unit has a double switch digital electronic thermostat with setback.

The 750 and 1000 watt units work fine. The 2500 watt unit emits a low buzz or hum when it is running. It is in my home theater area of the basement so the sound it makes is objectionable. Any thoughts what could be causing this?

I tried to dampen various parts/areas of the heater with my hands, but was unable to determine the source of the sound. Please help!

Assuming the voltage delivered to the heater is correct, 240 volts, I believe the humming is the actual element that runs the entire length of the heater.

If I remember correctly, a 2500 watt heater is a 10 foot long unit. The heating element is a tube with the fins pressed onto the tube, and the entire assembly sits in clips or metal cradles of some sort.The element probably is loose in these clips on purpose to allow the element to expand and contract due to it getting hot.

Perhaps you can eliminate some or most of the noise by tightening these clips or cradles to a point of stopping the noise, but still loose enough for the element to expand and contract.

Considering the almost 10 foot long element is in a metal housing 10 foot long, the slight hum of the element is being amplified by the housing, like a large metal musical instrument.

Or perhaps the metal housing is humming and needs to be tightened somehow. Or maybe loosening the mounting screws that hold the heater to the wall can be loosened a bit. Or try putting nylon washers behind the heater at each mounting screw.

See if any of these ideas make sense and work for you.

Me, I would probably be lazy and just kick up the volume on the theater equipment, but that me, king of laziness.

Let us know if any of these work.

I have the same problem. What was your solution scrappy_dude?

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Originally Posted by sdonk

I have the same problem. What was your solution scrappy_dude?

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I did not do anything. It somehow went away by itself with use. Maybe the continued expanding and contracting as it heated up and cooled down changed something to cause it to go away.

I have the same problem with my 8 foot 220 volt baseboard heater. I installed a 4 foot and 6 foot 220 volt heater. They work as they should with no humming. But my 8 foot has a humming/buzzing when it is on. I had a single pole thermostat and switched to a double pole thermostat. The humming/buzzing is still there. I was told it may have to do with the longer wire. Something to do with magnet force field. And a loose wire. Well I am not into force be with me luke. So I am taking it back and trying another one. Oh the knob thermostats from Honeywell are not accurate. I tried four of them. They clicked at different temperatures. But the Honeywell digital thermostat I do like. Always use double pole/four wires thermostats for a 220 volt heater. And again the heater is not to make a humming/buzzing sound. Anything loose could cause a short and make cause more problems.