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  • HOME electrical wireing question.

    so my best from from university had an interesting issue today ....


    I guess someone plugged in a vacuum cleaner turned it on , . and sparks started flying out of the outlet.

    after a moment the plug had melted, and fallen off leaven lots of burn marks and the 2 prongs in the outlet.


    so - I happen to be there , and think .. okay .. lets have a look at this thing , ... breaker is off pull out the multimeter no voltage - good , as expected.
    we open up the outlet, and WTF - no ground ....I mention - this should be grounded. "oh yea, that's up here".

    I respond "ummm , grounding isn't something you can go and get "


    "nope I got it he says" .....

    turns out what the electrician did was went out and bought some USED GFCI DUPLEX outlets, .. and ran them inline for the circuits over the house. so beside his breaker panel, he has a "wall of GFCI plugs".

    I verified, after we reset these, that the outlets is wired 110volt (hot to neutral-no gnd).

    so

    q1) - why did the vacuum freak out. I can only guess it has something to do with the inductive load (vacuum motor), and no ground. will he have this issue always with no ground outlets?

    q2) Why did BOTH the breaker on the panel and GFCI on the "wall of plugs" trip. I would have though that the first one tripping, would prevent the second. (unless - and a long shot here - the back emf, from the running motor tried to go through the GFCI as kinda a shunt in the path, once the breaker had already gone ---- motor with stored energy in rotation turns in to generator?....)

    q3) do inductive loads do anything of specific consequence to GFCI?

    cheers folks.
    and also I know this is an AUDIO board, but hopefully this general discussion will glean some interesting facts about the audio related issues we face.
    -token canadian

    Lest we forget: double-blind tests make audiophiles look twice as stupid. CRAIG V 2007

    Just for fun, what do you think would happen if you decided to take a nap in the fast lane of a freeway? agedhorse -2008

    Funny, I'll bet I have a good one sitting on my shelf. agedhorse -2008

  • #2
    #1 you should have grounded outlets and devices throughout your house. If the wiring is old and you cannot afford to rewire you should not replace the 2 prong ungrounded old outlets with newer 3 prong jobs. It covers up a mess and is dangerous.
    #2 a ground fault outlet is suppposed to be ran with a ground in parellel so it has something to monitor for .... the ground faulting. Using one inline is nornal for a circuit, i.e. you don't need a ground fault in every plug if there is one in the run, but they are not going to give any ground fault or extra overload protection if there is no ground wire running through the circuit and the gfi.
    #3 the breaker tripped because the hot came back through the neutral as the vacuum was melting and shorting out, just as the gfi outlet let it's spring loose due to over current.

    the vac had a bad chord or a motor shorted out, or the outlet was damaged and shorted when you plugged it in. the fact that the breaker did not trip until it started melting makes me fearful of your system- you do not have a breaker over 15-20 amps on an outlet circuit do you?
    Remember These Daze

    Comment


    • #3
      #1 you should have grounded outlets and devices throughout your house. If the wiring is old and you cannot afford to rewire you should not replace the 2 prong ungrounded old outlets with newer 3 prong jobs. It covers up a mess and is dangerous.
      #2 a ground fault outlet is suppposed to be ran with a ground in parellel so it has something to monitor for .... the ground faulting. Using one inline is nornal for a circuit, i.e. you don't need a ground fault in every plug if there is one in the run, but they are not going to give any ground fault or extra overload protection if there is no ground wire running through the circuit and the gfi.
      #3 the breaker tripped because the hot came back through the neutral as the vacuum was melting and shorting out, just as the gfi outlet let it's spring loose due to over current.

      the vac had a bad chord or a motor shorted out, or the outlet was damaged and shorted when you plugged it in. the fact that the breaker did not trip until it started melting makes me fearful of your system- you do not have a breaker over 15-20 amps on an outlet circuit do you?


      Okay, let's clear up a few things before this gets totally out of hand.

      A GFCI does not need a ground in order to operate. In fact, the ground is superfluous to the operation of a GFCI. A GFCI works by sensing the current flow on the hot, and the the current flow on the neutral. It compares the two current flows, and if there is a difference of more than ~5 milliamps, this indicates a fault...that current is going somewhere else like through a person...and shuts off power.

      The GFCI does not monitor current against the ground if a ground is present. It's a common mistake..."ground faults" are not faults in the grounding system, they are faults *to* ground...current leaking to earth ground via a body or some other conductive part.

      What the electrician did is code-legal and safe. Ungrounded GFCI-protected receptacles are in fact safer for personal protection than grounded receptacles without GFCI protection.

      Installing a GFCI in a branch circuit is the best solution for old buildings that are not conducive to expensive wiring renovation. This can either be with a GFCI outlet or plain-front, or a GFCI breaker if one is available for the panelboard.
      "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

      Comment


      • #4
        so my best from from university had an interesting issue today ....


        I guess someone plugged in a vacuum cleaner turned it on , . and sparks started flying out of the outlet.

        after a moment the plug had melted, and fallen off leaven lots of burn marks and the 2 prongs in the outlet.


        so - I happen to be there , and think .. okay .. lets have a look at this thing , ... breaker is off pull out the multimeter no voltage - good , as expected.
        we open up the outlet, and WTF - no ground ....I mention - this should be grounded. "oh yea, that's up here".

        I respond "ummm , grounding isn't something you can go and get "


        "nope I got it he says" .....

        turns out what the electrician did was went out and bought some USED GFCI DUPLEX outlets, .. and ran them inline for the circuits over the house. so beside his breaker panel, he has a "wall of GFCI plugs".

        I verified, after we reset these, that the outlets is wired 110volt (hot to neutral-no gnd).

        so

        q1) - why did the vacuum freak out. I can only guess it has something to do with the inductive load (vacuum motor), and no ground. will he have this issue always with no ground outlets?

        q2) Why did BOTH the breaker on the panel and GFCI on the "wall of plugs" trip. I would have though that the first one tripping, would prevent the second. (unless - and a long shot here - the back emf, from the running motor tried to go through the GFCI as kinda a shunt in the path, once the breaker had already gone ---- motor with stored energy in rotation turns in to generator?....)

        q3) do inductive loads do anything of specific consequence to GFCI?

        cheers folks.
        and also I know this is an AUDIO board, but hopefully this general discussion will glean some interesting facts about the audio related issues we face.


        1. It's anybody's guess why the vacuum freaked. Most likely a short or partial short. Has nothing to do with the lack of ground. It should be noted that in the case of a fully grounded system, if the device plugged in has no grounded cordset a grounded outlet is of no matter at all, and if it does have a grounded cordset, only a physical fault to a grounded portion of the device (let's say a metal case for a vacuum cleaner) will utilize the ground, and it'll only trip the breaker if the fault draws considerable current...15 or 20 amps depending on the branch circuit...for a long enough period. Any other fault, such as a person being shocked, will not necessarily draw sufficient current through the hot wire to trip the OCP.

        2. Both devices tripping is likely only a coincidence of timing. Residential breakers have both magnetic and thermal elements. The magnetic responds quickly to very high current draw, and the thermal responds slowly to lower current. In this case, I'd guess that the thermal element heated enough that it was just about to trip when the GFCI tripped. Inductive current from the motor would not be a factor if the GFCI had tripped...a complete circuit is still a requirement for inductive current flow.

        3. Yes, very inductive loads can cause a "false" trip of a GFCI. It's rare for a normally operating vacuum cleaner to cause a false trip in my experience.
        "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

        Comment


        • #5
          Additionally, it should be noted that as of the 2002 NEC, bedroom circuits must be protected by an arc-fault circuit interrupter. This device has the ability to detect arcing. Arcs can often draw less current than the OCP requires to trip, but are a common cause of residential fires.

          The 2008 NEC has expanded the location requirements to just about every general use receptacle circuit that doesn't have a GFCI requirement.
          "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

          Comment


          • #6
            Craig's comments are spot on.

            It's possible that there was a loose connection at the plug, or a partial short in the cordset. This can cause excessive heating and arcing at the connection.

            Breakers tripping simultaneously is a function of trrip coordination. This timing is not exact by any means. It's not the indication of anything unusual.

            RockStringBendr should study up on electrical theory, it's woefully lacking in correctness.
            -------------------------------------------------------------------------------------------------------------------------------------------------------------------
            Former product development engineer: Genz Benz, a KMC Music/FMIC/JAM Industries Company, continuing factory level product support and service for Genz Benz

            Currently product development engineer: Mesa Boogie

            Comment


            • #7
              okay , so sufice to say at the end of teh day ...


              the real issue her ewas not the wireing - but rather the vacume. It is simply a coincidence that it happened in a house that recently have some wireing altered.

              The current situation of hot/nuet/ NO grnd, is as safe as can be, with the addition of the GFCI.

              will the lack of a ground pose any other issues for the operation of electronic .. TV/ Stereo, playstation, ... ect.?
              -token canadian

              Lest we forget: double-blind tests make audiophiles look twice as stupid. CRAIG V 2007

              Just for fun, what do you think would happen if you decided to take a nap in the fast lane of a freeway? agedhorse -2008

              Funny, I'll bet I have a good one sitting on my shelf. agedhorse -2008

              Comment


              • #8


                will the lack of a ground pose any other issues for the operation of electronic .. TV/ Stereo, playstation, ... ect.?


                Typically, no it should not pose a problem for the actual operation of these devices. The grounding system is in place to "clear fault currents"; in other words to trip the breaker when voltage is placed on exposed conductive parts. All exposed conductive parts are supposed to be bonded to ground. In theory this is great, but in practice the breaker only trips and protects a person if the current is high enough to trip the breaker. There are many circumstances such as leaking insulation, where current is not this high, but voltage can be lethal or cause injury or a fire. That's why GFCI and AFCI devices are employed.
                "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

                Comment


                • #9
                  Craig's comments are spot on.

                  It's possible that there was a loose connection at the plug, or a partial short in the cordset. This can cause excessive heating and arcing at the connection.

                  Breakers tripping simultaneously is a function of trrip coordination. This timing is not exact by any means. It's not the indication of anything unusual.

                  RockStringBendr should study up on electrical theory, it's woefully lacking in correctness.


                  +1 on Craig V comments also.

                  My money is on the vac having a molded end AC plug with countless yanks out of the outlet from 10 feet away....
                  Considering the "meltdown" point....
                  I preach using the plug itself to remove from an outlet to my guys who are helping on rig tear down or any plug removal period.
                  Now if I can get people in my household to pull on the plugs !

                  Investigated a housefire that ended up being started by bed casters sitting on top of a very old brown zip extension cord - and was in a spare bedroom that hadn't been used for months until the night before the fire. Hmmmm.
                  Hence another reason for the arc fault (AFCI) requirement. Also found 14-2 romex in that bedroom breakered at 20 amp......whatever....

                  And on people misunderstanding GFCI function - I have found so many who just do not really know how it works. They see "ground fault" in the name and off we go ! A shame on the deaths that have occurred because of skipping the use of GFCI where it really needed to be.

                  Deric

                  Comment


                  • #10
                    So wait, is this why there's a GFI outlet in the garage near the breaker box that's on the same circuit as the outlets in our master bathroom? Our house was built about 10 years ago so I always figured the contractors just screwed up and forgot to put one in the bathroom so they just stuck one by the breaker box and called it a day. Is that normal practice? Usually I see them in the bathroom themselves in modern houses.
                    basses:
                    ~1986 pearl white fretless Fender Jazz Bass Special | 1978 black on black, maple neck Fender Precision | dark shadow grey Fender Power Jazz Bass Special | Novatone Precision!? | a couple of uprights

                    equipment:
                    Sunn 1200s & 410h cabinet | too many other bass amps to list
                    Akai Deep Impact | Akai Unibass | Ashly DPX-200 | Korg DT-10 tuner | a few pedals I don't use

                    Comment


                    • #11
                      So wait, is this why there's a GFI outlet in the garage near the breaker box that's on the same circuit as the outlets in our master bathroom? Our house was built about 10 years ago so I always figured the contractors just screwed up and forgot to put one in the bathroom so they just stuck one by the breaker box and called it a day. Is that normal practice? Usually I see them in the bathroom themselves in modern houses.


                      It can definitely be done that way "on purpose". Some feel that excessive moisture will degrade a GFCI faster, so locating it out of the bathroom would prevent this. It would be more expensive but cleaner to have installed a GFCI breaker in the panel. The breaker version costs about $40.

                      But if they used a GFCI receptacle remotely, I'd replace them with blank-front GFCI's. It looks like a 'normal' GFCI but has no outlets.


                      This way nobody tries to use the receptacle in the garage for something else. If the GFCI is 10 years old, it is probably near the end of its useful life so replacing it isn't a big issue.

                      It would also be a good idea to label that GFCI for what it protects, for the sake of anyone else in your house....and the next guy if you sell.


                      When replacing any GFCI be sure to check the branch circuit's current rating, and buy either a 15- or 20-amp GFCI depending on that rating. I often see 20-amp branch circuits with 15-amp GFCI's.
                      "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

                      Comment


                      • #12
                        Well, of course we've got a deep freeze plugged into it as it's the only outlet available in the garage Curses, you cheapskate, corner cutting developers!

                        It's weird cause the other bathroom has the GFCI outlet in the bathroom like normal. There's a couple in the kitchen behind the counter too but I suppose they're not subject to the clouds of steam like one in a bathroom would be.

                        So, what we need to do is get some outlets on their own circuit installed in the garage. Hrmph.
                        basses:
                        ~1986 pearl white fretless Fender Jazz Bass Special | 1978 black on black, maple neck Fender Precision | dark shadow grey Fender Power Jazz Bass Special | Novatone Precision!? | a couple of uprights

                        equipment:
                        Sunn 1200s & 410h cabinet | too many other bass amps to list
                        Akai Deep Impact | Akai Unibass | Ashly DPX-200 | Korg DT-10 tuner | a few pedals I don't use

                        Comment


                        • #13
                          Yes, a fridge or freezer should always be on its own 20a circuit. Note that in the garage location, it should be okay (check with your AHJ to be sure about your actual code) to have a single (not duplex) Edison receptacle without GFCI for a freezer. Even though you apparently had no false trip problems, it's not unusual for an inductive load such as a compressor motor to cause a GFCI to trip. That's the last thing you want, especially if you don't check the freezer every day.
                          "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

                          Comment


                          • #14
                            my comments were basically driven by my understanding of code and you do not re-device a home with a grounded device if there is no ground wires in the circuit. It is bad form and practice. if you cannot afford to rewire the house putting a GFI in the circuits will not protect anything needing a return to ground for safety unless you drive a 20 foot ground rod into the earth and attach a lead to each 3 prong device.

                            May have convoluted my response but I know the dos and don't of wiring a home or light commersial strycture.

                            Thyat guyz electrican has an add-on 'let's try this instead of doing it right' hazard setup in the dude's home and it's rigged like something from Wiring For Dummies. I don't like or approve of the setup. Come on, the dude stated that he was getting a ground from a GFI in a circuit without a ground wire. How much more do I need to learn to understand that he is either a moron or a BS'r?

                            I also did not say that the lack of a ground caused the issue, rather that the vac had an issue.
                            Remember These Daze

                            Comment


                            • #15
                              if you cannot afford to rewire the house putting a GFI in the circuits will not protect anything needing a return to ground for safety unless you drive a 20 foot ground rod into the earth and attach a lead to each 3 prong device.


                              A GFCI will work the same whether there is a ground or not. A GFCI will shut off power faster and at a much smaller leakage than any grounded circuit. Would you rather be hit with 12 amps leaking into a 15amp grounded circuit...still not enough to trip the breaker...or the 5 milliamps that trips a GFCI? You need to undertstand that a human body's resistance high enough that it will not cause enough current flow to trip a circuit breaker. You'll be dead long before a trip. This is part of the reason for GFCI's.
                              "If you don't know where you are going, you might wind up someplace else" - Yogi Berra, 1925-2015

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