# Electrical question **URL:** \ **Category:** Factual Questions\ **Created:** [October 6, 2015, 1:16pm UTC](https://boards.straightdope.com/t/electrical-question/733706 "2015-10-06T13:16:28Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![Me\_Billy](https://avatars.discourse-cdn.com/v4/letter/m/e480ec/32.png) [@Me\_Billy](https://boards.straightdope.com/u/Me_Billy)\ **Post date:** [October 8, 2015, 4:10pm UTC](https://boards.straightdope.com/t/electrical-question/733706/21 "2015-10-08T16:10:20Z")
> [@carnivorousplant](#): > > To some extent it is a money making scheme. A state licensed electrician installed a load center for me, and I still had to pay a company certified by the state to examine it. He took the cover off, peered inside and said, “That’s great. Seventy five adollars”. :dubious: You should see some of the “not up to code” work out there they do not pass! Like this… [http://inspectapedia.com/electric/LowVoltageGERelayBox020DFs.jpg](http://inspectapedia.com/electric/LowVoltageGERelayBox020DFs.jpg) Or this… [http://staticassets-hrd.appspot.com/i1xevrbkp/693x428\_crop.jpg](http://staticassets-hrd.appspot.com/i1xevrbkp/693x428_crop.jpg) Anyway the insurance company wants to see electrical work inspected before they will insure the house. They DON’T want to insure a house with improper wiring! ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 8, 2015, 5:40pm UTC](https://boards.straightdope.com/t/electrical-question/733706/22 "2015-10-08T17:40:31Z")
> [@Me\_Billy](#): > > Anyway the insurance company wants to see electrical work inspected before they will insure the house. They DON’T want to insure a house with improper wiring! The insurance company insisted that I have a 100 Ampere load center. The state electrician who did it was an artist. Wire going to circuit breakers looked like he had bent them in 90 [sub]0[/sub] with pliers. 🙂 However, the gas company is happy to come and inspect things if I just ask them. No $75 fee. 🙂 ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 8, 2015, 5:43pm UTC](https://boards.straightdope.com/t/electrical-question/733706/23 "2015-10-08T17:43:53Z")
It benefits me and the insurance company. If they decline to pay based on the condition of the wiring, I can point out that they had it inspected. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [October 8, 2015, 10:31pm UTC](https://boards.straightdope.com/t/electrical-question/733706/24 "2015-10-08T22:31:45Z")
[https://www.google.com/search?q=how+to+wire+3+way+switch&safe=strict&espv=2&biw=1920&bih=1099&tbm=isch&tbo=u&source=univ&sa=X&ved=0CBwQsARqFQoTCIPRlMn2s8gCFc\_0gAodGRUJpg](https://www.google.com/search?q=how+to+wire+3+way+switch&safe=strict&espv=2&biw=1920&bih=1099&tbm=isch&tbo=u&source=univ&sa=X&ved=0CBwQsARqFQoTCIPRlMn2s8gCFc_0gAodGRUJpg) ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 10, 2015, 3:02am UTC](https://boards.straightdope.com/t/electrical-question/733706/25 "2015-10-10T03:02:09Z")
I have a Masters Degree in Instrumentation and Electronics, but I can not figure out why two dpdt switches constitutes a “three way switch”. ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [October 10, 2015, 3:36am UTC](https://boards.straightdope.com/t/electrical-question/733706/26 "2015-10-10T03:36:01Z")
> [@carnivorousplant](#): > > I have a Masters Degree in Instrumentation and Electronics, but I can not figure out why two dpdt switches constitutes a “three way switch”. It’s a XOR gate. If you consider 01 and 10 the same, then it has three states. ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [October 10, 2015, 6:15am UTC](https://boards.straightdope.com/t/electrical-question/733706/27 "2015-10-10T06:15:04Z")
> [@friedo](#): > > It’s a XOR gate. If you consider 01 and 10 the same, then it has three states. ??? No the DPDT switch can’t give you get 01 and 10 Its not two DPST’s, which can give you 01 and 10… DPDT is giving you 11 ,22 or OO (O for OFF, since its not a pole…) A three way switch is really a THREE POLE… (whether or not it has “off”) ---
**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\ **Post date:** [October 10, 2015, 6:19am UTC](https://boards.straightdope.com/t/electrical-question/733706/28 "2015-10-10T06:19:07Z")
A switch for power usually has an off, a “three way switch” is usually for signals ( sound, video, etc), which have no “off”… ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [October 11, 2015, 4:15am UTC](https://boards.straightdope.com/t/electrical-question/733706/29 "2015-10-11T04:15:18Z")
A DPDT switch can be wired up as a three way switch. ---
**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:** [October 11, 2015, 3:25pm UTC](https://boards.straightdope.com/t/electrical-question/733706/30 "2015-10-11T15:25:16Z")
[Switches come in a number of configurations](http://diyeffects.com/blog/wp-content/uploads/2010/08/switches.jpg). Four common ones are single pole single throw (SPST) single pole double throw (SPDT) double pole single throw (DPST) double pole double throw (DPDT) [Here](http://www.act-solutions.com/PCC/images/fig09.gif) is a schematic (not a wiring diagram) of a “three-way switch.” As you can see, it consists of two SPDT switches wired together. It is very easy to understand how it works by visualizing what happens when each switch is thrown. I think part of the confusion is that the term “three-way switch” can be applied to each SPDT switch or both SPDT switches when they’re wired together. Instead of using two SPDT switches, you can use two DPDT switches as mentioned by **Snnipe 70E** , and simply not use one of the poles in each switch. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 11, 2015, 9:21pm UTC](https://boards.straightdope.com/t/electrical-question/733706/31 "2015-10-11T21:21:19Z")
> [@](#): > > Quoth **Amateur Barbarian** : > > It’s technically illegal to do plumbing and electrical and other “code” work in a lot of places. Home Depot still sells as many switches, boxes and wirenuts there. Well, sure. No matter who’s doing the work, pro or amateur, they still need to buy the supplies somewhere. ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [October 11, 2015, 10:04pm UTC](https://boards.straightdope.com/t/electrical-question/733706/32 "2015-10-11T22:04:16Z")
In most places that I am familiar with, even if an electrician and/or inspector is required, you can still generally replace like with like. In other words, if you have an old house with 2 prong outlets and one breaks, you can go down to Lowes or Home Depot or some hardware store or whatever and you can replace it with another 2 prong outlet. This is why those stores are allowed to sell parts in areas where an electrician is required. What you can’t do is change it from a 2 prong to a 3 prong outlet yourself. You can replace, but any change requires an electrician or inspection or whatever is required locally. Similarly, if your light switch fails you can replace it, but you can’t install a dimmer switch yourself as that is a change and would require an electrician. ETA: I note that our OP hasn’t come back. I hope he didn’t electrocute himself. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [October 13, 2015, 12:10am UTC](https://boards.straightdope.com/t/electrical-question/733706/33 "2015-10-13T00:10:47Z")
> [@engineer\_comp\_geek](#): > > What you can’t do is change it from a 2 prong to a 3 prong outlet yourself. You can replace, but any change requires an electrician or inspection or whatever is required locally. That makes sense. I believe the inspection should be free or deductible from your homeowners. 🙂 One of my tenants replace two prong with three prong without telling me. The present tenant remarked that he wanted to, and told him not to tell me. You can’t just put the “Not grounded” sticker on it? [Previous page](https://boards.straightdope.com/t/electrical-question/733706.md?page=1)