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  1. #11
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by Lloyd View Post
    I think theres room for improvement within the NEC here, simply reying on a sticker to tell someone there is no egc doesnt replace a ground. I understand that article thanks for clearing that up for me ernie, I'll once again fall back on the NEC NOT being a guide for electrical instalations but instead a MINIMUM stadard. Load protecting outlets without an egc isnt something I would practice, IMO I think your better served with devices that have no egc provision (2prong)
    Lloyd, with a GFCI installed the ECG provides little if any protection other than what I described above..
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  2. #12
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    I think we had this conversation before Jack.

    The EGC also provides a path to ground for the bonded non current carrying parts of equipment or appliances that may be plugged into that outlet as well.

    For instance the metal housing of a drill motor.... metal cup in a milkshake maker metal door on a fridge ... etc

    even load protected by a gfi a difference in potential could still exist between any metal part of an appliance plugged in and any other metal part bonded (or not) to the gec.
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  3. #13
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by Lloyd View Post
    I think we had this conversation before Jack.

    The EGC also provides a path to ground for the bonded non current carrying parts of equipment or appliances that may be plugged into that outlet as well.

    For instance the metal housing of a drill motor.... metal cup in a milkshake maker metal door on a fridge ... etc

    even load protected by a gfi a difference in potential could still exist between any metal part of an appliance plugged in and any other metal part bonded (or not) to the gec.
    And if that difference in potential exists, so what? What protection does the ECG provide that would not be taken care of far faster by the GFCI?

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  4. #14
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by Lloyd View Post
    I think we had this conversation before Jack.

    The EGC also provides a path to ground for the bonded non current carrying parts of equipment or appliances that may be plugged into that outlet as well.

    For instance the metal housing of a drill motor.... metal cup in a milkshake maker metal door on a fridge ... etc

    even load protected by a gfi a difference in potential could still exist between any metal part of an appliance plugged in and any other metal part bonded (or not) to the gec.
    Lloyd --- Difference in potential is how the GFCI disconnects the load instead of relying on over current . GFCI's are intended for "personal safety " and to me they do that effectively --- albeit too effective at times but none the less they work fine.
    "" an ounce of perception -- a pound of obscure "
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  5. #15
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by Lloyd View Post
    I think theres room for improvement within the NEC here, simply reying on a sticker to tell someone there is no egc doesnt replace a ground. I understand that article thanks for clearing that up for me ernie, I'll once again fall back on the NEC NOT being a guide for electrical instalations but instead a MINIMUM stadard. Load protecting outlets without an egc isnt something I would practice, IMO I think your better served with devices that have no egc provision (2prong)
    Lloyd, I agree with your first sentence completely. {A small sticker in place of a ground wire?** But I believe the NEC just is covering all the bases on this one.

  6. #16
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by deadshort View Post
    Read through my 08 NEC Quote in post #8 and consider yourself confirmed.
    Thank you. To me, this is confirmation for what I would call "the best solution to meet code, to get 3-prongs everywhere, and not have to run new wire everywhere". I've been finding out that a GFCI protected outlet with no ground is safer for the elec device plugged in, and for personal safety; in comparison to a grounded non GFCI.

    Yes, some devices notice there is no ground (like an APC battery backup device) and they warn you of this but knowing it's protected by gfci is safe if not safer.

    I consider this one closed. That you for the copy/paste from the NEC.

  7. #17
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    Smile Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by katonkasno View Post
    I have a 1949 house, with 2-prong outlets and 2-wire system (no ground, even after opening the wrapping to check). All circuits are 20 amp, the panel is good. Also for safety I am checking for cracked rubber, and using shrink tube if any is exposed.

    Question: I want to upgrade some or all of my outlets to a 3-prong outlet. I installed 20 amp GFCI's where I needed these per the NEC(2-wire, no ground). If I install a 20 amp GFCI on the first outlet of a circuit, and supply the remaining outlets with the LOAD side... can I install regular 15 amp 3-prong outlets for the rest in the same circuit? And label them "No Equipment Ground" and "GFI Protected"?

    Thanks.
    You need to know that a GFI installed on an ungrounded system is completely useless as far as safety goes. The reason for this is the GFI basicaly measures the amount of current that leaves the hot side and compares it to the amount coming back on the neutral side if any of this current finds its way to the ground instead of the neutral you have the meaning of a "ground fault". If this occurs the GFCI device then shuts the current off within a half of a cycle,(1/120th of a second), To answer your question of the 15 amp receptacles on a 20 amp GFI circuit is completely approved by the code. The only way to correct a system wired with a nonmetalic sheathed cable that lacks a ground is to install a seperate ground for each receptacle by taking a cooper conductor the same size as the hot wire,(#12 AWG), and taking it to a cold water pipe or approved ground rod system. This is a lot of work. but I have found that most systems of the age of yours actually has a metalic ground somewhere in the sheath of the cable. Then you could just install a ground jumper to each metal box and receptacle,(both need to be grounded), and eliminate the need for the whole seperate ground system installation. I hope this helps you.DK (A card carrying electrician for 28 years.)

  8. #18
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by dankalen View Post
    You need to know that a GFI installed on an ungrounded system is completely useless as far as safety goes. The reason for this is the GFI basicaly measures the amount of current that leaves the hot side and compares it to the amount coming back on the neutral side if any of this current finds its way to the ground instead of the neutral you have the meaning of a "ground fault". If this occurs the GFCI device then shuts the current off within a half of a cycle,(1/120th of a second), To answer your question of the 15 amp receptacles on a 20 amp GFI circuit is completely approved by the code. The only way to correct a system wired with a nonmetalic sheathed cable that lacks a ground is to install a seperate ground for each receptacle by taking a cooper conductor the same size as the hot wire,(#12 AWG), and taking it to a cold water pipe or approved ground rod system. This is a lot of work. but I have found that most systems of the age of yours actually has a metalic ground somewhere in the sheath of the cable. Then you could just install a ground jumper to each metal box and receptacle,(both need to be grounded), and eliminate the need for the whole seperate ground system installation. I hope this helps you.DK (A card carrying electrician for 28 years.)
    Yes, running ground wire through the house is a big job since all water pipe has been converted to cpvc. I will do this where/when I can just for the sake of completeness and further safety.

    The original wires installed in 49 have absolutely no ground, but the upgraded wires from the 50s and 60s do.

  9. #19
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by dankalen View Post
    You need to know that a GFI installed on an ungrounded system is completely useless as far as safety goes. The reason for this is the GFI basicaly measures the amount of current that leaves the hot side and compares it to the amount coming back on the neutral side if any of this current finds its way to the ground instead of the neutral you have the meaning of a "ground fault". If this occurs the GFCI device then shuts the current off within a half of a cycle,(1/120th of a second), To answer your question of the 15 amp receptacles on a 20 amp GFI circuit is completely approved by the code. The only way to correct a system wired with a nonmetalic sheathed cable that lacks a ground is to install a seperate ground for each receptacle by taking a cooper conductor the same size as the hot wire,(#12 AWG), and taking it to a cold water pipe or approved ground rod system. This is a lot of work. but I have found that most systems of the age of yours actually has a metalic ground somewhere in the sheath of the cable. Then you could just install a ground jumper to each metal box and receptacle,(both need to be grounded), and eliminate the need for the whole seperate ground system installation. I hope this helps you.DK (A card carrying electrician for 28 years.)
    Sorry but but you are incorrect. A ground wire (bonding) or grounded system serves no function on a GFCI receptacle other than providing a grounded connection for devices plugged into it, lightening protection and a referance link for the neutral lead. A GFCI measures the current flow on the neutral and hot leads and trips if there is a difference in current flow it does not measure ground fault. A GCFI can be tripped by highly capacitive devices in which case there is a delay in current flow between the hot and neutral but no flow to ground. GCFI's provides user protection with or without ground. Another case is with MWBC in which case you have both legs of power coming into a box. If you were to short one hot leg to the other, no ground fault, The current flow on the hot of the GFCI would be greater than the current flow on the neutral of the GFCI and the GFCI would trip long before the 15 or 20 amp threshold required to trip a breaker. If both legs of the MWBC were GFCI protected both GFCI's would trip.

    Jack
    Last edited by JLMCDANIEL; 05-17-2010 at 12:34 PM.
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  10. #20
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    Default Re: Upgrading 2-prong to 3-prong in old 2-wire system

    Quote Originally Posted by dankalen View Post
    You need to know that a GFI installed on an ungrounded system is completely useless as far as safety goes. The reason for this is the GFI basicaly measures the amount of current that leaves the hot side and compares it to the amount coming back on the neutral side if any of this current finds its way to the ground instead of the neutral you have the meaning of a "ground fault". If this occurs the GFCI device then shuts the current off within a half of a cycle,(1/120th of a second), DK (A card carrying electrician for 28 years.)
    Hmmm ---
    First thing ---- GFI stands for Ground Fault Interrupter --- add Circuit Interrupter for GFCI , which don't require a dedicated bare or green bonded ground conductor to function.

    With an "ungrounded" circuit you can still have a ground fault in a sense.
    Ground can be earth ground or any other ground .

    For example ---- the condition when a fault to ground exists, say someone touching a hot wire.
    Current flows in through the hot lead but then it splits. Some flows through the load (if the load is turned on) and some flows through a hapless victim to ground.

    Because there is more current flowing through the hot wire than through the neutral , there is a proportional imbalance between the hot and neutral leads , the sense circuit signals a comparator.

    When the sense circuit input becomes equivalent to 5 ma imbalance in current flow in the main leads, the comparator switches stage and generates a trip signal. This trip signal is applied to a coil that trips the main normally closed contacts. These contacts open and break the circuit to our hapless victim, saving their very
    thin heart and his life.

    Note ---- that none of this relies on the green wire.

    This is why GFI or GFCI work and provide personal safety to ungrounded circuits.


    Last edited by canuk; 05-17-2010 at 04:54 PM.
    "" an ounce of perception -- a pound of obscure "
    - Rush

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