Buzzing heater circuit

[ccschoch]

Hey y'all, I've got a breaker supplying a baseboard heater occasionally putting out a high pitched buzzing noise. Once it's going, turning the t-stat down kills the buzzing, as does flipping the heater breaker. But I can't reliably reproduce the buzzing.

My initial thought was arcing to the bus, but I would think a loose breaker would arc relatively consistently. That leaves me thinking it's something mechanical within the breaker as it approaches overload. The panel is an old ITE.

All that is on the circuit is a t stat and the heater. Any thoughts?

 

[LarryFine]

Pull the breaker and look.

 

[ccschoch]

Pull the breaker and look.

This is in my apartment, and I rent. Maintenance dude doesn't care if it can't be reproduced, and I don't have the okay from the complex to open it up. And I don't want the liability of opening it and having the complex blame me for any issues (they know I'm an electrical contractor).

I'm not personally too concerned, but it is annoying. I just want a solid theory to present to maintenance (which I think I already have). I was just curious if anyone had run into something similar. I've got a primarily new construction commercial/industrial background, so troubleshooting older residential isn't my forte.

 

[Dennis Alwon]

I have seen breakers make that noise. You can probably replace the breaker and be done with it. Not sure what causes it other than large loads.

 

[synchro]

Does the thermostat have a "heat intensity" or similar setting on it? If so then I suspect that the thermostat may be phase controlling the waveform of the line voltage using a triac to adjust the heat level. A phase controlled waveform has a lot of harmonic content that can cause or enhance buzzing in electrical components. Perhaps the magnetic trip element of a breaker could buzz from such harmonics. I'm sure that you've experienced such buzzing with light dimmers.

 

[ccschoch]

Does the thermostat have a "heat intensity" or similar setting on it? If so then I suspect that the thermostat may be phase controlling the waveform of the line voltage using a triac to adjust the heat level. A phase controlled waveform has a lot of harmonic content that can cause or enhance buzzing in electrical components. Perhaps the magnetic trip element of a breaker could buzz from such harmonics. I'm sure that you've experienced such buzzing with light dimmers.

The thermostat is a basic mechanical one, there shouldn't be any non linear loads.

 

[hbiss]

I'm not personally too concerned, but it is annoying. I just want a solid theory to present to maintenance

You tell them it buzzes and it's annoying. Fix it or I'm not paying rent until you do! There's your theory.

That's the way we handle things like that here in NY...

-Hal