# Making 20v circuits at hom...just for fun of course. **URL:** \ **Category:** Factual Questions\ **Created:** [January 7, 2004, 4:44pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231 "2004-01-07T16:44:19Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![Matchka](https://avatars.discourse-cdn.com/v4/letter/m/77aa72/32.png) [@Matchka](https://boards.straightdope.com/u/Matchka)\ **Post date:** [January 7, 2004, 4:44pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/1 "2004-01-07T16:44:19Z")
I’ve done it by accident and could do it again on purpose as needed but…How exactly do you make a 220v circuit at home? From what I can figure it’s just a matter of tapping 2 wires into the hot bus bar and 2 to the neutral—makes for an exciting hair drying experience when you do this by accident to a 110 outlet. But what’s going on? How is having 2 wires from the same source, and grounding at the same point different from just one? Is the bus really 220v? If it is then how can I get 110v out of that? Is this why real electricians have licenses? ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 7, 2004, 4:48pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/2 "2004-01-07T16:48:18Z")
It’s really two 110 V lines which are 180[sup]o[/sup] out of phase from one another. The pole transformer is actually feeding your house 220 V, center-tapped to provide two 110 V circuits. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 7, 2004, 4:53pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/3 "2004-01-07T16:53:38Z")
Errrr…scratch the 180[sup]o[/sup] bit. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [January 7, 2004, 5:31pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/4 "2004-01-07T17:31:57Z")
> [@](#): > > \*Originally posted by Q.E.D. \* > \*\*It’s really two 110 V lines which are 180[sup]o[/sup] out of phase from one another. The pole transformer is actually feeding your house 220 V, center-tapped to provide two 110 V circuits. \*\* A friend of mine ran a 220 appliance off the outlets in his house. As **Q.E.D** said, US houses are wired with center-tapped 220 V. power. from the center tap (_i. e._ the white wire) to either line is 110 V. and the lines are out of phase so that from line to line there is 220 V. So if you find two outlets one of which is wired to one of the 110 V. circuit and the other is wired to the opposite 110 V. circuit you have a source of 220 V. power **THIS IS DANGEROUS AND SHOULDN’T BE DONE UNDER ANY CIRCUMSTANCES** but my friend was a Ph.D. physicist and an Associate Professor of Physics at the University of Wisconsin, Madison, which probably explains his actions. ---
**Author:** ![MaryEFoo](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@MaryEFoo](https://boards.straightdope.com/u/MaryEFoo)\ **Post date:** [January 7, 2004, 6:13pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/5 "2004-01-07T18:13:24Z")
Craft guys do it right. Engineers do it their way: better than right. Physics professors do it much, much better than right. ---
**Author:** ![SendIt](https://avatars.discourse-cdn.com/v4/letter/s/50afbb/32.png) [@SendIt](https://boards.straightdope.com/u/SendIt)\ **Post date:** [January 7, 2004, 6:22pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/6 "2004-01-07T18:22:11Z")
Umm… Maybe I’m missing something, but isn’t it normal to have appliances on a 220V line? I have an electric stove on one. ---
**Author:** ![bughunter](https://avatars.discourse-cdn.com/v4/letter/b/aeb1de/32.png) [@bughunter](https://boards.straightdope.com/u/bughunter)\ **Post date:** [January 7, 2004, 6:33pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/7 "2004-01-07T18:33:34Z")
Yes, but the electricians who wire the outlets run the circuit thru dedicated breakers or fuses, and the separate 110v legs are not distributed to other outlets, except maybe to one other appliance in the same room. And since no one else has cleared up the phase issue, at least in this thread: the legs are out of phase 120°, so that the voltage on all three lines of a three-phase main always adds up to 0v. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [January 7, 2004, 6:40pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/8 "2004-01-07T18:40:54Z")
> [@](#): > > \*Originally posted by bughunter \* > \*\*And since no one else has cleared up the phase issue, at least in this thread: the legs are out of phase 120°, so that the voltage on all three lines of a three-phase main always adds up to 0v. \*\* Not quite, which is why I retracted my 180° statement. That’s because it depends. If it’s a center-tapped secondary, then the circuits are 180° out of phase, and the L-L voltage is 220. If it’s two legs of a three-phase secondary, then the circuits are 120° out of pahse and the L-L voltage equals the L-N voltage / SQRT(3), or 208 V. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [January 7, 2004, 6:52pm UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/9 "2004-01-07T18:52:31Z")
Just to clarify, you need _two_ things to produce 220 V from two 110 V AC sources: 1. They must be 180 degrees out of phase 2. They must share a common conductor ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [January 8, 2004, 5:22am UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/10 "2004-01-08T05:22:02Z")
> [@](#): > > \*Originally posted by bughunter \* > **Yes, but the electricians who wire the outlets run the circuit thru dedicated breakers or fuses, and the separate 110v legs are not distributed to other outlets, except maybe to one other appliance in the same room.** The breakers on a 220 V. circuit are ganged together so that if one goes, they both go. This isn’t true if you haywire two separate 110 V. circuits to get 220. In the haywire case something can blow the breaker on one side and could cause a serious problem with a 220 V. appliance using the circuits. > [@](#): > > \*\*And since no one else has cleared up the phase issue, at least in this thread: the legs are out of phase 120°, so that the voltage on all three lines of a three-phase main always adds up to 0v. \*\* I’ve never encountered it, but apparently in some localities two phases of a three phase system are used for domestic power. In these places bughunter’s statement is correct. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [January 8, 2004, 10:35am UTC](https://boards.straightdope.com/t/making-20v-circuits-at-hom-just-for-fun-of-course/223231/11 "2004-01-08T10:35:39Z")
> [@](#): > > \*Originally posted by bughunter \* > **And since no one else has cleared up the phase issue, at least in this thread…** Let’s just say it was something of a sensitive issue around here for a while. 😉 Although judging by the other posts in the thread, it’s becoming less so. 🙂