You can't just connect your voltmeter to mains and then select DC on some low range; the meter will be overloaded by the AC component.
Don't worry, I used Fluke 287 which is safe to use for such purpose, see my reply to kizzap below.
Have a look at this rather long thread. Toward the end I discuss the possibility of DC on the mains in your house:
http://forum.allaboutcircuits.com/showthread.php?t=37358
Thank you, great info
![ThumbsUp :-+](https://www.eevblog.com/forum/Smileys/default/icon_smile_thumbsup.gif.pagespeed.ce._JElyJQqdB.gif)
, it may take a while for me to digest it all though.
![Embarrassed :-[](https://www.eevblog.com/forum/Smileys/default/xembarrassed.gif.pagespeed.ic.zcm3EmNu9T.png)
But the experiment with hair dryer is interesting, I will try it and report back.
Dc on the mains was a problem years ago when colour TV sets were being introduced. Phillips made the G11, which used a half wave switchmode power supply ( a thyristor connected in series with the mains and controlled by the HT voltage, it would typically draw a 11A pulse every second mains cycle) that caused quite a few distribution transformers to catch fire from the high DC current saturating the core, as it had never been designed to have a 100A or so DC current flow ( as these were all UK sets they were all wired correctly so all the current pulses added up) in addition to the regular load, and the core material ran out of it's linear region and saturated. Later transformers were designed with larger cores and a small air gap distributed around the core to reduce saturation. That is why half wave rectifier power supplies are outlawed in most countries for any load over 10W or so.
The half wave rectifier, is that a direct rectifying the mains using high voltage rectifier without using a transformer ?
Are there other common house hold electronics that you aware of that can caused that DC flow ? Even they're banned now.
I am curious as to how you were measuring the DC voltage, as in what it was relative to. If it was ground, aka a ground pike plugged into ground, then yes it can be a bad thing. There is a reason that Neutral is tied to Earth in the power distribution box.
I used Fluke 287, it can display something like this below, but in my experiences, I never spotted any DC voltage, as they're always zero, while the AC voltage is spot on.
Example from Fluke manual, these are just the variations on how to display AC and DC at the Fluke 287/9 display.
![](https://www.eevblog.com/forum/beginners/beginner-what-multimeter-would-you-guys-recommend-budget-$50-to-$100/?action=dlattach;attach=68681;image)