# US House wiring question **URL:** \ **Category:** Factual Questions\ **Created:** [March 28, 2011, 2:42pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265 "2011-03-28T14:42:03Z")\ **Posts on this page:** 15\ **Page:** 3
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 29, 2011, 2:02pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/41 "2011-03-29T14:02:34Z")
> [@septimus](#): > > The one key thing I’ve learned: When, e.g., replacing a lightbulb, it’s better to switch off the double-throw circuit breaker, rather than just the single-throw wall switch. > > Question: posters speak of appliances where neutral and ground are connected. Are these not obsolete, since they’re incompatible with GFCI ? > > Question 2: > Wasn’t the main breaker double throw? :dubious: 😕 > [@thelabdude](#): > > The main breaker will be double pole, single throw. I see references to double throw breakers on forums, but never saw one. Double pole means it switches 2 connections, often the 2 legs of a single phase circuit. Double throw means having a common that can be switched from normally open to normally closed. A 3 way light switch is an common example. They also come in center off for some applications. it seems that double pole was being referred to. there are disconnects that are as if they were a DPDT circuit breaker for switching between two incoming power sources (the grid and a backup generator ) for residential. it could be a mechanical means that turns one main incoming breaker off when the other main incoming breaker goes on, two separate breakers with a mechanical linkage. both md2000 and septimus gave some very scary situations. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [March 29, 2011, 2:21pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/42 "2011-03-29T14:21:56Z")
While there are double pole, double throw switches, can you give me a link to a double throw breaker? ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [March 29, 2011, 2:36pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/43 "2011-03-29T14:36:31Z")
> [@Inigo\_Montoya](#): > > Like outlets for lamps that are to be activated by light switches. Gawd I hate those things. I undo them whenever I get the chance. > > The hole goes DOWN, light switches operate LIGHTS. > This is canon per the OCD code and is beyond…contestation. Cite? The National Electrical Code Section 406.4 (D), the Canadian Electrical Code, nor the Council for the Harmonization of Electromechanical Standards of the Nations of the Americas (CANENA) have specifications as to the orientation of NEMA connector receptacles. Secondly, switches are used to operate or disconnect power to lights, receptacles, or any permanently connected machinery or equipment ie your furnace or bathroom exhaust fans. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 29, 2011, 2:52pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/44 "2011-03-29T14:52:46Z")
> [@Inigo\_Montoya](#): > > Like outlets for lamps that are to be activated by light switches. Gawd I hate those things. I undo them whenever I get the chance. depending on the situation it may be required by the electrical code in the USA. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 29, 2011, 5:06pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/45 "2011-03-29T17:06:06Z")
> [@thelabdude](#): > > I see references to double throw breakers on forums, but never saw one. > [@johnpost](#): > > there are disconnects that are as if they were a DPDT circuit breaker for switching between two incoming power sources (the grid and a backup generator ) for residential. it could be a mechanical means that turns one main incoming breaker off when the other main incoming breaker goes on, two separate breakers with a mechanical linkage. > [@thelabdude](#): > > While there are double pole, double throw switches, can you give me a link to a double throw breaker? there are manual generator service entrance panels for residential use that act as if they were a DPDT main circuit breaker. for example [http://products.schneider-electric.us/products-services/products/load-centers/backup-power-connection/qo-generator-panels/](http://products.schneider-electric.us/products-services/products/load-centers/backup-power-connection/qo-generator-panels/) ---
**Author:** ![septimus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/septimus/32/410_2.png) [@septimus](https://boards.straightdope.com/u/septimus)\ **Post date:** [March 29, 2011, 5:16pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/46 "2011-03-29T17:16:37Z")
> [@johnpost](#): > > it seems that double pole was being referred to. > … > both md2000 and septimus gave some very scary situations. Yes, double-pole. Sorry to use the wrong term. We use 220 Volts here, significantly deadlier than U.S. 120 Volts. The “good” news is that (due to various infrastructure inadequacies?) there’s usually only about 150 Volts coming into our house. :smack: ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [March 29, 2011, 6:10pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/47 "2011-03-29T18:10:50Z")
> [@johnpost](#): > > there are manual generator service entrance panels for residential use that act as if they were a DPDT main circuit breaker. > > for example > > [http://products.schneider-electric.us/products-services/products/load-centers/backup-power-connection/qo-generator-panels/](http://products.schneider-electric.us/products-services/products/load-centers/backup-power-connection/qo-generator-panels/) Nope, that isn’t a double throw breaker, just 2 mechanically linked single throw breakers. > [@Sparky812](#): > > Cite? > The National Electrical Code Section 406.4 (D), the Canadian Electrical Code, nor the Council for the Harmonization of Electromechanical Standards of the Nations of the Americas (CANENA) have specifications as to the orientation of NEMA connector receptacles. > Secondly, switches are used to operate or disconnect power to lights, receptacles, or any permanently connected machinery or equipment ie your furnace or bathroom exhaust fans. I am sorry I can’t cite the section but there is one place where the code does specify the ground up, where oxygen is in use. Look around in any medical facility, all the outlets have the ground on top. That is to prevent sparking in case something conductive falls on a partly unplugged plug. Many people devoutly believe code calls for it everywhere. I see tons of cords meant to run down from a ground down outlet doubled over in a ground up one. ---
**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:** [March 29, 2011, 6:28pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/48 "2011-03-29T18:28:23Z")
The NEC doesn’t specify ground up or down for outlets. However, local codes might. In one place I used to live, local codes specified ground down. Right across the river (which happened to be in another state) the local codes specified ground up. YGMV (your ground may vary). ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 29, 2011, 6:46pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/49 "2011-03-29T18:46:51Z")
> [@thelabdude](#): > > I see references to double throw breakers on forums, but never saw one. > [@johnpost](#): > > there are disconnects that are as if they were a DPDT circuit breaker for switching between two incoming power sources (the grid and a backup generator ) for residential. it could be a mechanical means that turns one main incoming breaker off when the other main incoming breaker goes on, two separate breakers with a mechanical linkage. > [@johnpost](#): > > there are manual generator service entrance panels for residential use that act as if they were a DPDT main circuit breaker. > > for example > > [http://products.schneider-electric.us/products-services/products/load-centers/backup-power-connection/qo-generator-panels/](http://products.schneider-electric.us/products-services/products/load-centers/backup-power-connection/qo-generator-panels/) > [@thelabdude](#): > > Nope, that isn’t a double throw breaker, just 2 mechanically linked single throw breakers. i never said it was a double throw breaker. i said that it, ‘act as if they were a DPDT main circuit breaker.’ it makes it hard to know what you are referring to without a link to the forums you read or a quote. what i referred to might be called a double throw breaker by someone because it effectively acts like one. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [March 29, 2011, 6:57pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/50 "2011-03-29T18:57:11Z")
there is much debate and discussion on forums about the ground being up or down on receptacles. unless in local code there is a choice. many like the looks better with the ground down. many will have the ground up so that a right angle plug lays the cord in the desired direction. many will have the ground up if using metal cover plates or if things are able to drop on the prongs of a plug not fully inserted (like a work bench with lots of things hanging above the plug). ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [March 29, 2011, 7:14pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/51 "2011-03-29T19:14:13Z")
> [@thelabdude](#): > > Nope, that isn’t a double throw breaker, just 2 mechanically linked single throw breakers. > > I am sorry I can’t cite the section but there is one place where the code does specify the ground up, where oxygen is in use. Look around in any medical facility, all the outlets have the ground on top. That is to prevent sparking in case something conductive falls on a partly unplugged plug. Many people devoutly believe code calls for it everywhere. I see tons of cords meant to run down from a ground down outlet doubled over in a ground up one. > [@engineer\_comp\_geek](#): > > The NEC doesn’t specify ground up or down for outlets. However, local codes might. In one place I used to live, local codes specified ground down. Right across the river (which happened to be in another state) the local codes specified ground up. > > YGMV (your ground may vary). > [@johnpost](#): > > there is much debate and discussion on forums about the ground being up or down on receptacles. unless in local code there is a choice. > > many like the looks better with the ground down. > > many will have the ground up so that a right angle plug lays the cord in the desired direction. many will have the ground up if using metal cover plates or if things are able to drop on the prongs of a plug not fully inserted (like a work bench with lots of things hanging above the plug). Hold on, I am not disputing that the orientation may depend on their location, use, or local codes. Actually, I admit to being whooshed by **Inigo Montoya** as I missed the [OCD](http://en.wikipedia.org/wiki/Obsessive%E2%80%93compulsive_disorder) reference in his post.:smack: ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [March 29, 2011, 7:34pm UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/52 "2011-03-29T19:34:25Z")
> [@Sparky812](#): > > Actually, I admit to being whooshed by **Inigo Montoya** as I missed the [OCD](http://en.wikipedia.org/wiki/Obsessive%E2%80%93compulsive_disorder) reference in his post.:smack: I am nothing if not a weasel. I know I’m an authority on nothing. 😉 I really shouldn’t be allowed in this forum. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [March 30, 2011, 3:28am UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/53 "2011-03-30T03:28:07Z")
[QUOTE=beowulff] AC is AC - it doesn’t matter what the polarity is. There’s no way that reversing the polarity of an outlet could cause damage to a single-phase appliance. [/QUOTE] I offer the smoldering remains of a TV as my cite. I used to have a TV that was for its time, a typical “hot chassis” design where if the receptacle is wired right, the chassis is connected directly to the neutral or grounded conductor. As the grounded conductor (aka neutral) and the grounding conductor (aka ground) are bonded to each other and earth ground at the service entrance, it’s a perfectly safe design if everything is wired properly. As it turned out, one outlet in my apartment was wired hot-neutral reverse, so the TV’s chassis was electrically hot. Between plastic knobs and remote control, it was rare that I ever touched the TV. Until that fateful day when cable TV came. When it’s installed properly, the coax shield is earth-grounded. When the coax came into contact with the socket on the TV, there was a zap and a crack and the magic smoke leaked out of the TV and the cable box. The cable box was plugged into a properly wired outlet, so it was grounded along with the coax. The net result was one fried TV, one fried cable box, and a tripped breaker. So yes, a mis-wired outlet can damage an appliance. ---
**Author:** ![andrewm](https://avatars.discourse-cdn.com/v4/letter/a/c57346/32.png) [@andrewm](https://boards.straightdope.com/u/andrewm)\ **Post date:** [March 30, 2011, 3:50am UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/54 "2011-03-30T03:50:09Z")
> [@gotpasswords](#): > > I offer the smoldering remains of a TV as my cite. > > I used to have a TV that was for its time, a typical “hot chassis” design where if the receptacle is wired right, the chassis is connected directly to the neutral or grounded conductor. As the grounded conductor (aka neutral) and the grounding conductor (aka ground) are bonded to each other and earth ground at the service entrance, it’s a perfectly safe design if everything is wired properly. > > As it turned out, one outlet in my apartment was wired hot-neutral reverse, so the TV’s chassis was electrically hot. Between plastic knobs and remote control, it was rare that I ever touched the TV. Until that fateful day when cable TV came. When it’s installed properly, the coax shield is earth-grounded. When the coax came into contact with the socket on the TV, there was a zap and a crack and the magic smoke leaked out of the TV and the cable box. The cable box was plugged into a properly wired outlet, so it was grounded along with the coax. The net result was one fried TV, one fried cable box, and a tripped breaker. > > So yes, a mis-wired outlet can damage an appliance. Similar experience here, connecting some old (early transistorized) audio equipment to a modern, grounded oscillator. The result was a huge spark that took chunks out of the plug and socket and a tripped breaker, but fortunately no fried equipment. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 30, 2011, 3:54am UTC](https://boards.straightdope.com/t/us-house-wiring-question/576265/55 "2011-03-30T03:54:31Z")
> [@gotpasswords](#): > > I offer the smoldering remains of a TV as my cite. > > I used to have a TV that was for its time, a typical “hot chassis” design where if the receptacle is wired right, the chassis is connected directly to the neutral or grounded conductor. As the grounded conductor (aka neutral) and the grounding conductor (aka ground) are bonded to each other and earth ground at the service entrance, it’s a perfectly safe design if everything is wired properly. > > As it turned out, one outlet in my apartment was wired hot-neutral reverse, so the TV’s chassis was electrically hot. Between plastic knobs and remote control, it was rare that I ever touched the TV. Until that fateful day when cable TV came. When it’s installed properly, the coax shield is earth-grounded. When the coax came into contact with the socket on the TV, there was a zap and a crack and the magic smoke leaked out of the TV and the cable box. The cable box was plugged into a properly wired outlet, so it was grounded along with the coax. The net result was one fried TV, one fried cable box, and a tripped breaker. > > So yes, a mis-wired outlet can damage an appliance. Not anything made in the last, oh, 40 years… [Previous page](https://boards.straightdope.com/t/us-house-wiring-question/576265.md?page=2)