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Thread: Splitting ground

  1. #1
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    Splitting ground

    I'm on a project with a 600 amp service and the owner of this project asked why we can't split the ground into two (smaller) wires running to water meter, instead of paying for the one thicker cable. I said it isn't allowed but I don't know where to reference it from in the NEC. Can anyone help?

  2. #2
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    Grounding electrode conductors (GEC) are in T250.66, there is no provision anywhere in that table or section that allows the use of two smaller GEC's to make a larger one. The largest ever required is #3/0 which isn't very big so I'm unsure why your boss would want to run two cables smaller than that.
    Rob

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    All responses based on the 2014 NEC unless otherwise noted

  3. #3
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    Grounding has a minimum size and so does bonding, but, water meters are usually bonded with a 10 pr 12 guage wire..so how is that too much.. unless code has changed? Even most cable splitters are usually bonded with a 12 or 14 guage..
    or has that changed? Used to wonder why we bonded the splitters on rentals until after I saw lightning hit a trailer park... the trailers that had the cable and telephone stuff bonded to ground spikes were fine, but the three that had no bonding lost almost all electrics and one of them caught fire... the lightning had hit a tree about a hundred feet away.. four trailer closer were all fine...
    ever since then, even my amateur radio splitters for my receivers are all bonded to ground.

  4. #4
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    Quote Originally Posted by Adamjamma View Post
    Grounding has a minimum size and so does bonding, but, water meters are usually bonded with a 10 pr 12 guage wire..so how is that too much.. unless code has changed? Even most cable splitters are usually bonded with a 12 or 14 guage..
    or has that changed? Used to wonder why we bonded the splitters on rentals until after I saw lightning hit a trailer park... the trailers that had the cable and telephone stuff bonded to ground spikes were fine, but the three that had no bonding lost almost all electrics and one of them caught fire... the lightning had hit a tree about a hundred feet away.. four trailer closer were all fine...
    ever since then, even my amateur radio splitters for my receivers are all bonded to ground.
    Greetings Adamjamma,

    The applications you are talking about are purely lightning concerns to the best I can ascertain and have rules in other chapters, such as Chapter 8 which deal with your experiences. However, in chapter 2, more specifically article 250 we have rules for GEC's because they could experience transient surge voltages, lightning voltages and other over voltages that result in currents and it has been determined as a basic minimum safety standard that sizing will be dictated by 250.66.

    Sadly i am not sure I can elaborate any more on that until after a few cups of java but I will give it more thought and share more when my epiphany kicks in my good man.


    Paul W. Abernathy
    Electrical Code Academy, Inc.
    CMP #5 and #17
    *All code responses are based on the 2017 National Electrical Code®[NEC®]

  5. #5
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    Quote Originally Posted by Adamjamma View Post
    Grounding has a minimum size and so does bonding, but, water meters are usually bonded with a 10 pr 12 guage wire..so how is that too much.. unless code has changed? Even most cable splitters are usually bonded with a 12 or 14 guage..
    or has that changed? Used to wonder why we bonded the splitters on rentals until after I saw lightning hit a trailer park... the trailers that had the cable and telephone stuff bonded to ground spikes were fine, but the three that had no bonding lost almost all electrics and one of them caught fire... the lightning had hit a tree about a hundred feet away.. four trailer closer were all fine...
    ever since then, even my amateur radio splitters for my receivers are all bonded to ground.
    We don't bond water meters, we use metal underground piping for a grounding electrode. We have to make a bonding jumper around things in that piping such as a meter though. The GEC is 8 AWG or larger and has been for very long time.

    Bonding for art 800 items is often smaller conductors. Why do we bond them - to equalize voltage potential between systems.
    I live for today, I'm just a day behind.

  6. #6
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    But all incoming services, water, cable, tv aerials, ham radio antennas, cab antennas, telephone services, etc... are required to be bonded to the main grounding electrode, or if too far from there, to the nearest electrode location that is bonded to the main electrode by bonding jumpers of at least 8 guage wire between electrodes...
    there is a similar code 8n the UK, that has just been changed to say that if the service comes into the property in an insulated pipe, such as gas in plastic pipe, water in pvc pipe, etc, then you do not need to bond these to the grounding system as they will not bring in transients or allow faults from your property to cause problems elsewhere in the services... this is in the bonding and grounding sections..,
    or have I misunderstood all the YouTube videos and other items on grounding and bonding? Which is not just for lightning protection, although it helps stop the problems caused by having ground rods not bonded to each other.. equipotential bonding...
    but also to send any faults introduced within your residence to ground rather than allowing them to continue to a neighbors home and damage their belongings... if your water pipes are not bonded to ground and a short in your place causes your pipes to be carrying line voltage, and your neighbor also has not bonded their pipes... and the water pipes between the two places are metal... then your short circuit could electrocute your neighbor..
    not that common.., but has happened apparently in apartments or townhouses...

  7. #7
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    Quote Originally Posted by kwired View Post
    We don't bond water meters, we use metal underground piping for a grounding electrode. We have to make a bonding jumper around things in that piping such as a meter though. The GEC is 8 AWG or larger and has been for very long time.

    Bonding for art 800 items is often smaller conductors. Why do we bond them - to equalize voltage potential between systems.
    Ok.. so this is not l8ke the water meters that fall under services bonding in 800.100 etc... where 14 guage or larger is the code... yet I have never needed to bond water pipes in most structures due to plastic pipes being used... however, in UK, 7ntil the newest code goes in effect in January, need to bond inside even if service is plastic, if any copper pipes are inside... newest code recognizes that pvc and other plastic pipes insulate the incoming water lines, and even drop the requirement for bonding the metal taps on plastic sinks...

  8. #8
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    We must "bond" interior metal piping systems.

    A metallic water pipe that is buried in earth for 10 feet or more is one of the grounding electrodes mentioned in art 250.52. 250.50 says if present we must use it as part of the grounding electrode system.

    Water pipe electrodes typically will have lower resistance then a ground rod will, there often is more then just 10 feet of pipe in the earth and the more there is the lower the resistance likely will be. So it is required mostly because it is a good electrode.
    I live for today, I'm just a day behind.

  9. #9
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    Quote Originally Posted by kwired View Post
    We must "bond" interior metal piping systems.

    A metallic water pipe that is buried in earth for 10 feet or more is one of the grounding electrodes mentioned in art 250.52. 250.50 says if present we must use it as part of the grounding electrode system.

    Water pipe electrodes typically will have lower resistance then a ground rod will, there often is more then just 10 feet of pipe in the earth and the more there is the lower the resistance likely will be. So it is required mostly because it is a good electrode.
    So why does it seem everyplace is putting plastic pipes? Cost? Plastic lasting longer? Because I see more water line breakage in areas where plastic has replaced galvanized pipes... especially if metallic water pipes would be a better ground than ground rods, wouldn’t the general building codes such as The International codes call for it over the use of ground rods? Instead of all these TT, TNS etc grounding methods?

  10. #10
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    Quote Originally Posted by Adamjamma View Post
    So why does it seem everyplace is putting plastic pipes? Cost? Plastic lasting longer? Because I see more water line breakage in areas where plastic has replaced galvanized pipes... especially if metallic water pipes would be a better ground than ground rods, wouldn’t the general building codes such as The International codes call for it over the use of ground rods? Instead of all these TT, TNS etc grounding methods?
    Metal water pipes are not so popular anymore for various reasons. NEC simply says if you have metallic water pipe of 10 feet or more buried in the ground you must use it for a grounding electrode.

    Years ago they were all metal pipes, and we must still use them for a grounding electrode for existing applications. I can't recall seeing a new metal water pipe for main supply (especially in a dwelling) for at least 20 years or more.
    I live for today, I'm just a day behind.

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