# Some ground fault interrupters act to break the whole circuit. Who knew? **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [September 22, 2023, 11:25pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564 "2023-09-22T23:25:41Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [September 22, 2023, 11:25pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/1 "2023-09-22T23:25:41Z")
Last night my wife washing up before going to bed and accidentally splashed some water into an electric socket which tripped the GFI, taking out the whole bathroom. I was unaware that a GFI could do that, but I just googled it and there are socket types and circuit breaker types. When I tried resetting it, nothing happened, even after a half hour. But it reset fine this morning. It had to dry and a half hour was not enough. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [September 22, 2023, 11:28pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/2 "2023-09-22T23:28:59Z")
GFCI receptacles I’ve seen have the ability to feed additional downstream receptacles. That way you need only one. Probably the way you’re wired. Lights should be on a separate circuit though. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [September 22, 2023, 11:47pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/3 "2023-09-22T23:47:19Z")
> [@Hari\_Seldon](#): > > I just googled it and there are socket types and circuit breaker types > [@GaryM](#): > > GFCI receptacles I’ve seen have the ability to feed additional downstream receptacles. That way you need only one. A circuit breaker type is installed at the panel. A socket (receptacle) GFCI will take out the entire circuit if it trips, but I’m not sure that it gives the same protection at other sockets in the same circuit? If it did, why would we need the circuit breaker type? I know we have some expert electricians on here, but I can’t remember who they are. ---
**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:** [September 22, 2023, 11:50pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/4 "2023-09-22T23:50:46Z")
The circuit breaker type are useful for direct-wired loads (things that don’t plug in to an outlet). They are probably slightly more reliable than the outlet GFCIs, also. And, yes - outlet GFCIs protect all downstream loads from a ground fault. ---
**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:** [September 23, 2023, 1:15am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/5 "2023-09-23T01:15:59Z")
A residential GFI detects if there’s a difference of more than 5 mA (or so) between hot and neutral. In your case, the splashing water probably created a temporary electrical path between hot and ground, thereby creating the differential current. ---
**Author:** ![Seanette](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/seanette/32/9139_2.png) [@Seanette](https://boards.straightdope.com/u/Seanette)\ **Post date:** [September 23, 2023, 1:43am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/6 "2023-09-23T01:43:52Z")
> [@Riemann](#): > > I know we have some expert electricians on here, but I can’t remember who they are. I’m sure my husband, @Bob_Blaylock, would not necessarily call himself an “expert”, but he is a professional electrician. Hope he decides to chime in on this one. ---
**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:** [September 23, 2023, 2:23am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/7 "2023-09-23T02:23:22Z")
Yup, that’s the usual way for them to work. One GFCI outlet protects everything downstream of it. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [September 23, 2023, 3:06am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/8 "2023-09-23T03:06:04Z")
> [@Chronos](#): > > everything downstream of it. “Downstream” (as used several times in this discussion) means “connected to the load terminals of the GFCI”. [![](https://www.electricaltechnology.org/wp-content/uploads/2020/03/Outlet-Connected-to-the-Load-Terminals-are-GFCI-Protected.png) ](https://www.electricaltechnology.org/wp-content/uploads/2020/03/Outlet-Connected-to-the-Load-Terminals-are-GFCI-Protected.png) The power goes into the GFCI at the Line terminals. The Load terminals are internally connected to the Line only if the GFCI is not tripped. ---
**Author:** ![Bob\_Blaylock](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_blaylock/32/3235_2.png) [@Bob\_Blaylock](https://boards.straightdope.com/u/Bob_Blaylock)\ **Post date:** [September 23, 2023, 9:15am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/9 "2023-09-23T09:15:24Z")
  It doesn’t look like there is much more for me to add to this discussion, that hasn’t already been said.  A circuit-breaker GFCI covers the entire branch circuit.  A ground fault anywhere in that circuit shuts off the whole circuit.   A receptacle-based GFCI covers that receptacle, and any other receptacles that are daisy-chained after it. If there are any receptacles in that branch circuit. before the GFCI, then those are not protected, a ground fault in them will not trigger the GFCI, and they will not be shut off if the GFCI is triggered.  A ground fault at the GFCI receptacle, or at any receptacles after it in the chain, will trigger it, and will shut off all of those receptacles. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [September 23, 2023, 10:44am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/10 "2023-09-23T10:44:04Z")
> [@Riemann](#): > > If it did, why would we need the circuit breaker type? I’m addition to what’s already been said, in old wiring, you may not be entirely sure what’s downstream of what, so it can be easier to put in a GFCI breaker at the panel to protect the whole circuit. ---
**Author:** ![Hari\_Seldon](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hari_seldon/32/5173_2.png) [@Hari\_Seldon](https://boards.straightdope.com/u/Hari_Seldon)\ **Post date:** [September 23, 2023, 3:08pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/11 "2023-09-23T15:08:01Z")
Let me add that there appears to be no slot in the main breaker box that controls the bathroom. Incidentally the building is only 10 years old so it is not an upgrade from an old installation of questionable construction. There is a legend in the breaker box and it shows two slots for “salle de bain”, namely 10B and 12A. The actual breakers are also labeled and there is no 10B at all and 12A does nothing in either bathroom (or anything else obvious). One of these days I will have to produce a correct legend. ---
**Author:** ![andrewm](https://avatars.discourse-cdn.com/v4/letter/a/c57346/32.png) [@andrewm](https://boards.straightdope.com/u/andrewm)\ **Post date:** [September 23, 2023, 4:35pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/12 "2023-09-23T16:35:14Z")
> [@Riemann](#): > > A socket (receptacle) GFCI will take out the entire circuit if it trips, but I’m not sure that it gives the same protection at other sockets in the same circuit? If it did, why would we need the circuit breaker type? 1. There are plenty of things that require GFCI protection but don’t plug in: hard-wired whirlpool bath tubs, hot tubs, pool equipment, etc. Those could be protected by a GFCI “dead front” device (same shape and size as a GFCI receptacle but with no sockets, only test/reset buttons on the face) but that requires all the extra trouble of putting a junction box somewhere and hooking up the GFCI, in addition to feeding it from a standard breaker. Easier to just use a GFCI breaker and be done with it. 2. Many of the first places to require GFCI protection (bathroom countertop receptacles, kitchen countertop receptacles, outdoor receptacles) are exactly the sort of wet locations where you don’t want to put a sensitive electronic device (like a GFCI receptacle). ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [September 23, 2023, 9:17pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/13 "2023-09-23T21:17:44Z")
> [@Riemann](#): > > A socket (receptacle) GFCI will take out the entire circuit if it trips, but I’m not sure that it gives the same protection at other sockets in the same circuit? If it did, why would we need the circuit breaker type? That’s inaccurate, or at least sufficiently ambiguous to be wrong in some reasonable interpretations. See electrician @Bob_Blaylock’s post for the correct info. ---
**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:** [September 23, 2023, 10:41pm UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/14 "2023-09-23T22:41:11Z")
I’m guessing the EM field propagation speed in home wiring is around 0.5c. So practically speaking, there’s no difference in protection between a GFCI receptacle (or GFCI breaker) and any “downstream” receptacle. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [September 24, 2023, 12:22am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/15 "2023-09-24T00:22:23Z")
That’s true. What does matter though is understanding _which_ receptacles are downstream of which GFCI and which are not downstream of any. Expecting protection where it isn’t might be a nasty last surprise. If everyone could count on all buildings always being wired to all up-to-date electrical codes this would not be much of an issue. Sadly that’s not the situation. ---
**Author:** ![Retzbu\_Tox](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/retzbu_tox/32/11829_2.png) [@Retzbu\_Tox](https://boards.straightdope.com/u/Retzbu_Tox)\ **Post date:** [September 24, 2023, 12:35am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/16 "2023-09-24T00:35:33Z")
My house was built in 2008. I’m not sure of the rationale for this particular redundancy, but my kitchen and every bathroom in my house (anywhere there is a sink or bathtub) has both a Ground Fault Circuit Interrupt receptacle near the sink _ **and** _ an Arc Fault Circuit Interrupt breaker at the breaker panel. As far as I am aware, AFCI breakers would be valid protection for any room where an occupant might accidentally drive a nail into the wiring while hanging a picture or otherwise damage the wiring, and not specifically in areas where there is water. ---
**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:** [September 24, 2023, 12:48am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/17 "2023-09-24T00:48:22Z")
AFCIs are specifically designed to detect arcs - that is, when there is a spark jumping between two conductors, such as what might happen if a rodent chewed through a wire and started to smoke. GFCIs will detect an arc from Hot to ground, but not from Hot to Neutral. ---
**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:** [September 24, 2023, 1:03am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/18 "2023-09-24T01:03:58Z")
> [@beowulff](#): > > AFCIs are specifically designed to detect arcs - that is, when there is a spark jumping between two conductors, such as what might happen if a rodent chewed through a wire and started to smoke. Right. Slight hijack, but what’s the latest on AFCIs? Last I heard, they caused lots of false trips. Some electricians recommended (off the record) removing them after inspection. ---
**Author:** ![GaryM](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/garym/32/241_2.png) [@GaryM](https://boards.straightdope.com/u/GaryM)\ **Post date:** [September 24, 2023, 3:59am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/19 "2023-09-24T03:59:06Z")
> [@Hari\_Seldon](#): > > One of these days I will have to produce a correct legend. There are several tools made for identifying which breakers are for a particular receptacle. You plug a small transmitter into the receptacle and then run a receiver across the breakers. It beeps and indicates the correct breaker. Turn off the breaker and the indicator light on the transmitter goes out to confirm that you’ve got the right one. This is a [later model](https://www.kleintools.com/catalog/electrical-testers/digital-circuit-breaker-finder-gfci-outlet-tester) of the one I use. It also indicates that the receptacle is wired correctly. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [September 24, 2023, 10:04am UTC](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564/20 "2023-09-24T10:04:05Z")
> [@Crafter\_Man](#): > > Slight hijack, but what’s the latest on AFCIs? Last I heard, they caused lots of false trips. Some electricians recommended (off the record) removing them after inspection. AIUI, the false-trip issue is almost entirely on circuits that drive electric motors. Such as your fridge, HVAC, or for some folks well pump or sump pump. Because the motor start-up surge is very similar to an arc surge. I suspect, but do not know, that late-model AFCI’s have largely solved the problem for modern motors. That ancient motor on your 1950s swamp cooler? Probably not. [Next page](https://boards.straightdope.com/t/some-ground-fault-interrupters-act-to-break-the-whole-circuit-who-knew/990564.md?page=2)