How Much DC is OK on a Power Line?

Well Jim, I'm certainly open to finding out I've been wrong about things. Its how we learn :)

As far as the earth connection, what I am talking about here is that the hot side of the line is measured with respect to the neutral (ground). So if there is a DC component present, the AC voltage will be shifted with respect to the neutral. *That*, since the neutral is tied to the earth connection, will take some current and will likely heat the wiring up in the process.

Now if you have as an example Eva's hair dryer, running on half power so it its only conducting when the diode conducts, I can see that that might be interpreted as DC. But, it can also be interpreted as harmonic distortion. I'm not arguing, IOW, that the phenomena does not exist, just the explanation. One could as easily argue that a 2nd harmonic in the output of an amplifier is a DC phenomena as well.

I would like to see Eva's scope readings, but the images don't load off of DIYaudio.

Ralph,

I am not dismissing what you are saying about odd harmonics. They can and do play havoc on AC power systems.

They can cause the secondaries of power distribution transformers to run hotter than normal. And yes be mechanically noisier than normal.

Harmonics.

http://www.fluke.com/fluke/twen/solutions/pq/troubleshooting-power-harmonics.htm

http://www.psihq.com/iread/harmonic.htm

Is DC offset the product of harmonics?
.

My balanced power conditioner (Isoclean) was humming/buzzing loudly, sometimes for hours, sometimes for days, with no predictable pattern, and this was on a dedicated line. I put the Channel Islands XDC-2 between the wall outlet and the Isoclean unit, and the problem immediately and permanently disappeared.