The tri-level condo I lease has nine electrical strip heaters, five to nine foot units, all fairly old. Other than the usual expansion/contraction noise, all are dead quiet except for one six-footer location in the living room where there is an annoying electrical hum (no rattling buzz). It's the kind of background hum I associate with some loudspeakers and power lines, though not as loud of course (initially I thought it was from outside). When the wall thermostat clicks off or is turned down, the hum stops. Replacing the old one with a new unit hasn't solved it, as I just noticed after a month. The only difference is the new unit takes a minute or two for the hum to start and then it gets progressively louder up to a point, only stopping with the thermostat, as before. The other baseboard unit on the same wall thermostat is a nine footer and is dead silent. The three living/dining room strip heaters are on a 220v breaker (two 110's joined together).

The maintenance man was just here and says his online research and calls to local electricians indicate this is a common problem with baseboard units, without a known solution. Is that true? My online research raises the possibility that it's new unit hum that will go away eventually. The fact that it's the same location makes us wonder if there's some kind of power problem at that point. Any ideas? Thanks,

 

Is the heater controlled by a thermostat on the heater or is it wall mounted and controlling multiple heaters. The normal noise you mention happens as the element heats but sometimes the thermostat can cause noise by how it allows the heater element to heat and cool while keeping the room at a given temperature. I think the older unit stats allow a bigger swing in temperature and the newer wall mount keep the element warmer between heating cycles. So temperature swing one guess. If the hum is instantly changing with power on/off after the unit is up to temperature then I would try getting something and pressing on the element while it is humming and see if it stops. If it stops them vibration would be the cause. About the only other thing I could suggest is going to a panel type wall heater if you just can't find the problem.

 

Wall thermostat that controls two units. Thanks for the ideas. Panel type is probably out of the question given that it's a leased condo and there's a sofa in front of half the unit's length (only place for it).