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  1. #1
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    Default A question about bonding

    This service is only 60 amp, so there will need to be a new panel and service upgrade if my clients buy. 60 year old house. The Square D panel holds the main service disconnect, and the wood box above it contains the meter.
    It looks like tidy work, and I could not find a problem with the remote panel. That panel is fed by a 60 amp breaker, upper right in the main panel.

    But in the main panel, there is no bond between the neutral bus and the panel box, at least I don't see one. Also, the ground wire attaches only to the neutral bus. So is it correct to say the bonding screw is missing?

    It looks as though grounding is only achieved by the conduit connecting the service panel to the meter box. Is the conduit an adequate grounding conductor here?

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  2. #2
    Guy W Opie's Avatar
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    Default Re: A question about bonding

    It does look like the bonding screw is missing in the panel. The conduit only bonds the meterpan to the panel.


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    Default Re: A question about bonding

    Of course, the bonding defect is but one of several problems pictured.


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    Default Re: A question about bonding

    Quote Originally Posted by John Kogel View Post
    Is the conduit an adequate grounding conductor here?
    Yes, the conduit is a conductor.

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    Default Re: A question about bonding

    Quote Originally Posted by Jimmy Roberts View Post
    Of course, the bonding defect is but one of several problems pictured.
    Hello Jimmy. Could you enlighten us? If the bonding screw was installed, what else would be needed?

    A proper tie-bar? Too sharp bending radii? Is there more?

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  6. #6
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    Default Re: A question about bonding

    Quote Originally Posted by John Kogel View Post
    It looks as though grounding is only achieved by the conduit connecting the service panel to the meter box. Is the conduit an adequate grounding conductor here?
    As long as the holes in the panel and meter base are not concentric knockouts with some concentrics left in the panel the conduit can be used as a conductor without the use of grounding bushings. Hard to tell from the pictures what the knockouts look like.


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    Default Re: A question about bonding

    Quote Originally Posted by James Duffin View Post
    As long as the holes in the panel and meter base are not concentric knockouts with some concentrics left in the panel the conduit can be used as a conductor without the use of grounding bushings. Hard to tell from the pictures what the knockouts look like.
    Thank you, James. There is one ring there, larger than the nut.

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    Default Re: A question about bonding

    Well I don't know about you folks, but the paper clip being used as a handle tie is just classic.

    I've seen pegs, nails and string before but this is the first I've ever seen a paper clip!


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    Default Re: A question about bonding

    Quote Originally Posted by Donald Farrell View Post
    Well I don't know about you folks, but the paper clip being used as a handle tie is just classic.

    I've seen pegs, nails and string before but this is the first I've ever seen a paper clip!
    It's a piece of copper wire bent to look like a paper clip.

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  10. #10
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    Default Re: A question about bonding

    Quote Originally Posted by John Kogel View Post
    This service is only 60 amp, so there will need to be a new panel and service upgrade if my clients buy. 60 year old house. The Square D panel holds the main service disconnect, and the wood box above it contains the meter.
    It looks like tidy work, and I could not find a problem with the remote panel. That panel is fed by a 60 amp breaker, upper right in the main panel.

    But in the main panel, there is no bond between the neutral bus and the panel box, at least I don't see one. Also, the ground wire attaches only to the neutral bus. So is it correct to say the bonding screw is missing?

    It looks as though grounding is only achieved by the conduit connecting the service panel to the meter box. Is the conduit an adequate grounding conductor here?
    John

    The main bonding jumper/screw must be installed but I can't tell with what means they are bonding the neutral to the metal can. If you notice they have a stranded aluminum jumper between the neutral terminal block and the neutral bus at the bottom of the panel.
    The RMC connecting the meter and service equipment should have a bonding bushing and then a bonding jumper from that bushing to the neutral terminal block or bus.

    It is important to understand that this arrangement does present parallel paths.. ie .. service neutral and metal conduit due to bonding. It is nearly impossible to eliminate that issue on the line side or suppy side of service equipment when RMC is used between the meter and metal enclosure containing the service equipment. If you have the NEC handbook there are a few pictorial examples in article 250 of what you have with the pictured panel as far as bonding.


  11. #11
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    Default Re: A question about bonding

    Quote Originally Posted by John Kogel View Post
    This service is only 60 amp, so there will need to be a new panel and service upgrade if my clients buy.
    Why? Have you performed a load calculation to determine that this 60A service is not adequate? A typical 2000 s.f. dwelling with gas appliances [no AC] only calcs out around 40-50A.


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    Default Re: A question about bonding

    Quote Originally Posted by John Kogel View Post
    It looks as though grounding is only achieved by the conduit connecting the service panel to the meter box. Is the conduit an adequate grounding conductor here?
    I don't think that's the case. It looks like there is a cold water pipe bond which very likely is being used as the means of grounding.

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    Default Re: A question about bonding

    Quote Originally Posted by dana1028 View Post
    Why? Have you performed a load calculation to determine that this 60A service is not adequate? A typical 2000 s.f. dwelling with gas appliances [no AC] only calcs out around 40-50A.
    No, I did not do a load calc, that is something an electrician might do.
    They need 100 amps minimum. The insurance companies want to see upgraded electrical, so as a rule, they will give the clients 60 days to upgrade. Not my decision.

    We use hydro-electric for everything here, range, dryer, water heater, and often heat.
    NG comes from the mainland by way of an underwater pipe, only since the early 90's. It was only cheap until they got people hooked on it.

    Quote Originally Posted by Corn Walker View Post
    I don't think that's the case. It looks like there is a cold water pipe bond which very likely is being used as the means of grounding.
    Yeah, but there is no jumper from the neutral bus to the panel box. All branch circuit grounds go to the panel box, not the neutral bus. How it is done in Canada.

    BTW, Roger, thanks. What you say confirms that there's a mistake here.

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    Default Re: A question about bonding

    Quote Originally Posted by John Kogel View Post
    Yeah, but there is no jumper from the neutral bus to the panel box. All branch circuit grounds go to the panel box, not the neutral bus. How it is done in Canada.
    Is the armored cable bonded at the water pipe? It looks like it might be, but the picture wasn't clear enough to tell. If so, and if that cable does not use a concentric knockout (or uses a grounding bushing) then it might be the point where the ground source is bonded to the panel enclosure.

    Which means the panel ground and neutral might be bonded outside of the enclosure and would still be wrong...


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    Default Re: A question about bonding

    Quote Originally Posted by Corn Walker View Post
    Is the armored cable bonded at the water pipe? It looks like it might be, but the picture wasn't clear enough to tell. If so, and if that cable does not use a concentric knockout (or uses a grounding bushing) then it might be the point where the ground source is bonded to the panel enclosure.

    Which means the panel ground and neutral might be bonded outside of the enclosure and would still be wrong...
    OK, I see what you mean. Right, we expect to see something better than that.

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    Default Re: A question about bonding

    Quote Originally Posted by Corn Walker View Post
    Is the armored cable bonded at the water pipe? It looks like it might be, but the picture wasn't clear enough to tell. If so, and if that cable does not use a concentric knockout (or uses a grounding bushing) then it might be the point where the ground source is bonded to the panel enclosure.

    Which means the panel ground and neutral might be bonded outside of the enclosure and would still be wrong...
    It may just be a terminology problem but the water pipe bond (if it exists) does not constitute the neutral bond with likely to be energized metal. One is the GEC system for the grounding electrodes for property protection and the other is the EGC which is for human safety from electrical shock.


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    Default Re: A question about bonding

    Quote Originally Posted by Roger Frazee View Post
    It may just be a terminology problem but the water pipe bond (if it exists) does not constitute the neutral bond with likely to be energized metal. One is the GEC system for the grounding electrodes for property protection and the other is the EGC which is for human safety from electrical shock.
    When I see a wooden box not a meter can (metal) and older insulation on older wiring such as pictured, I for one, think older pre-mid-sixties. that's non-grounding type receptacles, etc. old two-wire systems (such as K&T, i.e. no ground; older type NM undersized ground, etc.). Granted there's been multiple generations of work done subsequently, including more modern NM at the second panel, but apparently not everything was upgraded when the first, or the later second panel was added as the meter box is still wood. We don't know what's in that wooden box or ahead, or just outside; nor, can I say with certainty if there is a qualifying water service electrically conductive metallic pipe of sufficient length or depth outdoors to qualify as an electrode. Might not be metal water supply/service pipe, might be lead, might be run through tile pipe and not in contact with earth, etc.

    Last edited by H.G. Watson, Sr.; 04-22-2011 at 12:11 AM.

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    Default Re: A question about bonding

    A lot of valid points but surely there is no question of a "wooden box not a metal can". Isn't it the case that the wood is not a meter box but the back of a recess in the outside wall on which a metal meter can/box is mounted? Where else would the conduit be going? The supply to the meter box probably comes down inside the wall, not allowed on new work today, but often done in older houses. Not allowing the supply conduit in the wall on new work is presumably because it's somewhat more likely to start a fire, e.g. if there's a short in the meter box, or if the wall is drilled into, but the answer as to whether this should be mentioned or not I will leave to those with more experience than I.

    Quote Originally Posted by H.G. Watson, Sr. View Post
    When I see a wooden box not a meter can (metal) and older insulation on older wiring such as pictured, I for one, think older pre-mid-sixties. that's non-grounding type receptacles, etc. old two-wire systems (such as K&T, i.e. no ground; older type NM undersized ground, etc.). Granted there's been multiple generations of work done subsequently, including more modern NM at the second panel, but apparently not everything was upgraded when the first, or the later second panel was added as the meter box is still wood. We don't know what's in that wooden box or ahead, or just outside; nor, can I say with certainty if there is a qualifying water service electrically conductive metallic pipe of sufficient length or depth outdoors to qualify as an electrode. Might not be metal water supply/service pipe, might be lead, might be run through tile pipe and not in contact with earth, etc.



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    Default Re: A question about bonding

    Quote Originally Posted by H.G. Watson, Sr. View Post
    We don't know what's in that wooden box or ahead, or just outside; nor, can I say with certainty if there is a qualifying water service electrically conductive metallic pipe of sufficient length or depth outdoors to qualify as an electrode. Might not be metal water supply/service pipe, might be lead, might be run through tile pipe and not in contact with earth, etc.
    You are correct, HG, it is a dog's breakfast, so to speak and needs an experienced electrician's touch. The grounding by water pipe mentioned above is in fact non-existent, as seen by the long view here. That new water supply pipe is plastic!
    Thankfully, my clients have plans to install a suite in the basement, so top on the list is a new service, as mentioned above.

    Quote Originally Posted by Frank Norman View Post
    A lot of valid points but surely there is no question of a "wooden box not a metal can". Isn't it the case that the wood is not a meter box but the back of a recess in the outside wall on which a metal meter can/box is mounted?
    That's right, Frank. There is a round metal meter can in the box, typical for the age in our region. Not so typical for the lower states, where they install their service panels outside. The poco, BCHydro, have seen fit to install a new digital meter, rated for 200 amps, but it is still the old 60 amp service conductors.

    The total lack of a ground rod connection to the service panel raises an interesting point. The three wire circuits indicate correct grounding. The neutral conductor is bonded to the back of the meter can. Ever since the water supply pipes were replaced on this street, there has not been proper grounding of the equipment to earth.

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    Default Re: A question about bonding

    My gosh! I usually don't get the chance to comment because H.G & Jerry P. pick the pic's bones clean before I get to them

    No mention of the red grounded conductor, white grounding electrode conductor (if pipe 8ft in earth), or the fact that the Service Raceway only needs 'bonding' (not grounding) on one side.
    Also, whether there is a knock-out ring where the service raceway terminates is irrelevant (unless a 'bonding'- locknut is used). Standard lock-nuts are not code approved for the purposes of bonding service raceways. Is there a tie down for the back-fed Main? What is the maximum stab rating in the main panel feeding the submarine panel?

    My favorite, besides the apparent paper clip tie handle, is that they are using the panel cover screws as grounding terminals for the NM ground wires.

    If I've missed anything I apologize, did just a quick look and read thru.
    I'm sure some of my points have been commented on that I did not catch.
    I believe the OP's initial question has been covered.


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    Default Re: A question about bonding

    Again some good points, but some doubt or questions on others.

    About the favorite, I cannot see any NM ground wires fastened at the panel cover screw holes (the four tapped holes in the corners), only under the screws near the front of the panel edges provided for ground wires. Panels like this accommodate ground wires this way and do not have the separate grounding strip as seen on other and/or newer panels.

    What is it that should be mentioned about the white covered grounding electrode conductor (very typical of that time)? Gauge or colour? What would you say the impact was? If the colour is the issue I might guess "no impact" as no-one is mistaking this for anything other than grounding electrode conductor, so why mention the colour. Please excuse me if this is a stupid question - I am trying to learn.

    Now the red covered neutral "feed" wire is definitely unusual, but again what is the impact of it? Around here black insulated wire is typical for the neutral "feed" but must have both ends white-taped to distinguish it from the two black hot wires when the panel is being installed, but afterwards....? Having a red neutral with two black hots accomplishes the same thing, although not compliant with today's practice for colours. It seems likely no-one would recommend that money be spent on having the red conductor replaced or taped with white, so what am I missing regards what should be mentioned or recommended in a report?


    >

    Quote Originally Posted by bob smit View Post
    My gosh! I usually don't get the chance to comment because H.G & Jerry P. pick the pic's bones clean before I get to them

    No mention of the red grounded conductor, white grounding electrode conductor (if pipe 8ft in earth), or the fact that the Service Raceway only needs 'bonding' (not grounding) on one side.
    Also, whether there is a knock-out ring where the service raceway terminates is irrelevant (unless a 'bonding'- locknut is used). Standard lock-nuts are not code approved for the purposes of bonding service raceways. Is there a tie down for the back-fed Main? What is the maximum stab rating in the main panel feeding the submarine panel?

    My favorite, besides the apparent paper clip tie handle, is that they are using the panel cover screws as grounding terminals for the NM ground wires.

    If I've missed anything I apologize, did just a quick look and read thru.
    I'm sure some of my points have been commented on that I did not catch.
    I believe the OP's initial question has been covered.



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    Default Re: A question about bonding

    It appears the bonding screw (usually brass) is missing at the main neutral bus.

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    Default Re: A question about bonding

    Quote Originally Posted by Joe Klampfer View Post
    It appears the bonding screw (usually brass) is missing at the main neutral bus.
    But what would it bond to? There doesn't appear to be a suitable ground that anyone can point to. There could be a ground path there somewhere, but if not all a bonding screw would achieve is bonding the neutral conductor to an ungrounded enclosure, potentially energizing it and the water pipe it is already bonded to. That's why there should be a proper grounding conductor that is properly bonded to the panel enclosure.


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    Default Re: A question about bonding

    Quote Originally Posted by Corn Walker View Post
    But what would it bond to? There doesn't appear to be a suitable ground that anyone can point to.

    How about the armoured solid # 10 copper conductor exiting the left side of the panel ? I'd bet you a doughnut it terminates at a ground rod or main incoming water supply (or both).

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    Default Re: A question about bonding

    Quote Originally Posted by Corn Walker View Post
    potentially energizing it and the water pipe it is already bonded to.

    Ahhh, I would agree only IF the incoming water supply pipe is plastic, but I'd bet a second doughnut the incoming water pipe is copper (might even be galvainized back then) and was intended to be main system ground path.

    I'm not disputing if it is correct or not, that's just how things were done up here in that era.

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    Default Re: A question about bonding

    Quote Originally Posted by Joe Klampfer View Post
    Ahhh, I would agree only IF the incoming water supply pipe is plastic, but I'd bet a second doughnut the incoming water pipe is copper (might even be galvainized back then) and was intended to be main system ground path.

    I'm not disputing if it is correct or not, that's just how things were done up here in that era.
    See post 19 from John, where he noted the water supply piping had indeed been replaced with plastic.

    Last edited by Corn Walker; 04-25-2011 at 01:07 PM. Reason: missing link

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    Default Re: A question about bonding

    Quote Originally Posted by Frank Norman View Post
    Again some good points, but some doubt or questions on others.

    About the favorite, I cannot see any NM ground wires fastened at the panel cover screw holes (the four tapped holes in the corners), only under the screws near the front of the panel edges provided for ground wires. Panels like this accommodate ground wires this way and do not have the separate grounding strip as seen on other and/or newer panels.

    What is it that should be mentioned about the white covered grounding electrode conductor (very typical of that time)? Gauge or colour? What would you say the impact was? If the colour is the issue I might guess "no impact" as no-one is mistaking this for anything other than grounding electrode conductor, so why mention the colour. Please excuse me if this is a stupid question - I am trying to learn.

    Now the red covered neutral "feed" wire is definitely unusual, but again what is the impact of it? Around here black insulated wire is typical for the neutral "feed" but must have both ends white-taped to distinguish it from the two black hot wires when the panel is being installed, but afterwards....? Having a red neutral with two black hots accomplishes the same thing, although not compliant with today's practice for colours. It seems likely no-one would recommend that money be spent on having the red conductor replaced or taped with white, so what am I missing regards what should be mentioned or recommended in a report?>
    Red is an ungrounded (hot) conductor color. It should be replaced but then a new service should take care of that issue.


  28. #28
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    Default Re: A question about bonding

    Quote Originally Posted by Corn Walker View Post
    But what would it bond to? There doesn't appear to be a suitable ground that anyone can point to. There could be a ground path there somewhere, but if not all a bonding screw would achieve is bonding the neutral conductor to an ungrounded enclosure, potentially energizing it and the water pipe it is already bonded to. That's why there should be a proper grounding conductor that is properly bonded to the panel enclosure.
    Why would installing the main bonding screw energize a panel that is ungrounded (not connected to earth)??


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    Default Re: A question about bonding

    Quote Originally Posted by Roger Frazee View Post
    Why would installing the main bonding screw energize a panel that is ungrounded (not connected to earth)??
    Because the neutral conductor may be carrying some current (e.g. 15A load on one leg, 20A load on the other, resulting in 5A returning on the neutral leg). If the panel is not bonded to an earth ground, bonding it only to the neutral leg gives the panel a voltage potential of 120V relative to ground.

    Consider the home inspector standing in a water puddle and unscrewing the panel cover with a non-insulated screwdriver. That home inspector represents an additional path to ground and, depending on the resistance that home inspector's body presents, some percentage of the 5A current will take that route to reach ground. If there was a suitable earth ground present, the relative resistance compared to the inspector would be such that only a negligible amount of current would be carried by the inspector's body.

    As you no doubt know, this is the reason neutrals and ground are separate in remote panels. Because electrical current will take all available paths (proportional to resistance) to resolve voltage potential, any unbalanced current will be carried on both the neutral conductor as well as the ground conductor back to the service panel.


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    Default Re: A question about bonding

    Sorry to keep harping about this but I am still am hoping for an opinion re the impact of the colour in this case. If the panel is not replaced with a larger one with bigger wires, then why should the neutral wire have to be replaced? I understand red is the wrong insulation colour for a neutral wire, but in reality what would be the the impact on the homeowner or purchaser if it is not replaced?

    If it matters that the colour is wrong, then, rather than replacing it, the ends of the wire could be taped with white electrical tape to indicate neutral, as is done on black insulation on a neutral wire.

    If, instead of a neutral wire with red insulation, there was a hot wire with white insulation, I would be more concerned, since trusting the wire to be a grounded neutral because of its insulation colour could result in injury or worse if work is done without isolating the circuit.

    Quote Originally Posted by Roger Frazee View Post
    Red is an ungrounded (hot) conductor color. It should be replaced but then a new service should take care of that issue.



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    Default Re: A question about bonding

    Quote Originally Posted by Corn Walker View Post
    See post 19 from John, where he noted the water supply piping had indeed been replaced with plastic.

    Good eye CW... ok, now I agree, the problem is there is no ground point and the report comments should recommend one be installed by a licensed electrician.

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    Default Re: A question about bonding

    F.N. & J.K.

    I wish I could make out the bottom right both inside and outside corner of the first panel. Can't make out if that's a black insulated and a natural or white or even if a bare conductor heading off to the right below the second panel and continuing somewhere. Can't seem to see into/make out the bottom right of the first panel either, despite when I try to "blow it up".


    When those service entrance conductors are replaced (BTW thanks JK for the long shot and outside shot of the wooden box which appears to be not a box or enclosure at all but a building exterior surface alcove or nook with questionable framing support) - it explains much and exposes MORE issues, IMO, ex. looks awfully low down outside) and properly routed so as to NOT enter the service panel directly from above into the TOP with no sealing or provisions for condensate drainage other then into the service equipment; they will also (or should be also) be of the SAME LENGTH, and be routed within the bending radius parameters of their listing and size.



    Color coding and restrictions were (and may continue to be) different in the many of the Canadian Codes versus the U.S. model codes (not just electrical, example tinting of primers and cements & welds for plastic waste plumbing). Work continues with regards to "harmonizing" some differences between the U.S. and Canada relative to Standards and Codes pertaining to Electrical, for example we've recently made some adjustments to our allowable ampacity tables to coincide with Canadian restrictions.

    We have been quite strict regarding the "identification" and "reidentification" of conductors in the U.S. for quite some time, and the understood meaning of "natural" (not neutral) color.

    It was my understanding that similar restrictions are presently in place in your unammended national code, CSA standards, etc., however I'm not my sharpest today and I don't recall precisely at the moment and don't care to do the verification or reference work for you today. I suggest you refer to your own electrical service authority and code set for information on the issue. I don't recall identification (reidentification) of other than a natural or black insulated conductor, certainly not red, being allowed even in BC, as a neutral, a grounding conductor, or a ground/equipment grounding conductor, or a bonding conductor, on AC, are you saying it was/is allowed?

    I guess my monitor needs adjusting - hard to tell what is for sure red, for sure orange, and what might be red or orange in some of the pictures (at least for me). Really wish I could make out what was going on in the bottom 1/3rd of the service panel, the lower right corner, and just outside to the right.

    Last edited by H.G. Watson, Sr.; 04-26-2011 at 11:19 AM.

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    Default Re: A question about bonding

    Quote Originally Posted by Corn Walker View Post
    Because the neutral conductor may be carrying some current (e.g. 15A load on one leg, 20A load on the other, resulting in 5A returning on the neutral leg). If the panel is not bonded to an earth ground, bonding it only to the neutral leg gives the panel a voltage potential of 120V relative to ground.

    Consider the home inspector standing in a water puddle and unscrewing the panel cover with a non-insulated screwdriver. That home inspector represents an additional path to ground and, depending on the resistance that home inspector's body presents, some percentage of the 5A current will take that route to reach ground. If there was a suitable earth ground present, the relative resistance compared to the inspector would be such that only a negligible amount of current would be carried by the inspector's body.

    As you no doubt know, this is the reason neutrals and ground are separate in remote panels. Because electrical current will take all available paths (proportional to resistance) to resolve voltage potential, any unbalanced current will be carried on both the neutral conductor as well as the ground conductor back to the service panel.
    You can't equate low impedance paths with high impedance paths for current that returns to the source. If what you say is true and you would have dangerous current flow thru you to ground (earth) if the panel metal is not connected to earth then your also saying that dangerous current is flowing on any grounding electrode conductors terminated to the neutral buss (very low resistance that copper wire..) .

    Also remember that the service neutral is earthed at the transformer.

    There is a reason that the service equipment is intentionally earthed (grounded) but it is not to allow system current to return to the source at dangerous amperage. Current does return to the source on all available paths regardless of impedance/resistance. However current that would go to earth in your example is so insignificant it does not pose a threat to human safety.

    As long as the service neutral is intact (not open) and grounded at the transformer there would be no danger in touching the metal panel of the service equipment if it is ungrounded... with the main bonding screw installed. I'd be more worried if it wasn't installed in your example.


  34. #34
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    Default Re: A question about bonding

    HGW
    No I am not saying red is allowed on the neutral wire to the service panel. I think the issue here is not whether red neutral is allowed (it isn't, even in BC) but what is the impact if it is already there and in use. In other words what is the impact of not replacing it. The senior Electrical inspector I just talked to says that, unless the service is being replaced with a larger one, then because there is no significant negative impact caused by the existing red wire, he would not ask for it to be replaced. He would be OK with having it identified it with white tape. This is not in the code but it makes sense nevertheless. Since the drop is overhead, as it is here, they may have some concern about whether the red insulation has the necessary sunlight resistance. That is why white-taped black neutral wire is required for new overhead service installs rather than white wire which deteriorates in the sun. However they are not asking for anything to be done about existing white wires (or red ones). If the insulation has deteriorated then he suggests heat shrink tubing could be used over the wire. How you do this easily I did not ask.

    FN

    Quote Originally Posted by H.G. Watson, Sr. View Post
    F.N.
    ... I don't recall identification (reidentification) of other than a natural or black insulated conductor, certainly not red, being allowed even in BC, as a neutral, a grounding conductor, or a ground/equipment grounding conductor, or a bonding conductor, on AC, are you saying it was/is allowed?
    ...



  35. #35
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    Default Re: A question about bonding

    Quote Originally Posted by Roger Frazee View Post
    You can't equate low impedance paths with high impedance paths for current that returns to the source. If what you say is true and you would have dangerous current flow thru you to ground (earth) if the panel metal is not connected to earth then your also saying that dangerous current is flowing on any grounding electrode conductors terminated to the neutral buss (very low resistance that copper wire..)
    I'm not sure where you read that in what I wrote. Unless there is an earth ground on the other end of those conductors (e.g. the equipment ground at the receptacle is bonded to a separate ground instead of floated) then there is no current on those grounding conductors.

    Electricity will take ALL paths to ground, both low impedance and high impedance, and the amount of current traveling along each path is relative to the impedance of the path. So with my example 5A current on a low impedance neutral bonded to the enclosure, very little will likely pass through the inspector. But the assumption that the neutral is low impedance isn't always a prudent one, nor is the assumption that the impedance of a home inspector is relatively high.


    Also remember that the service neutral is earthed at the transformer.

    There is a reason that the service equipment is intentionally earthed (grounded) but it is not to allow system current to return to the source at dangerous amperage. Current does return to the source on all available paths regardless of impedance/resistance. However current that would go to earth in your example is so insignificant it does not pose a threat to human safety.
    It allows dangerous current to return to earth in the case of an open or high impedance neutral and it allows dangerous current to return to earth in the case of a fault.

    Whether the current on an un-bonded neutral is dangerous or not depends on the amount of unbalanced current (unfortunately it's not at all uncommon to have >15A imbalance) and the impedance of the service neutral compared to the path through the inspector.

    As long as the service neutral is intact (not open) and grounded at the transformer there would be no danger in touching the metal panel of the service equipment if it is ungrounded... with the main bonding screw installed. I'd be more worried if it wasn't installed in your example.
    Aside from an open neutral you can have a high neutral to earth voltage (NEV) that presents a hazard. Again it depends on the impedance and is based on the conditions of the system and that of the person touching the system (the inspector coming in from the rain is at higher danger than one that is dry).

    Bonding an otherwise ungrounded panel enclosure to neutral protects against low impedance faults (i.e. short circuit) but not against (some) high impedance faults (i.e. wet inspector + high NEV). Not bonding protects against (some) high impedance faults but not low. My intention was not to say that the latter was preferable to the former, but to point out that the lack of a properly bonded grounding conductor can lead to problems, even in a system where there are no low impedance faults. That's why I believe we can both agree that a proper grounding conductor bonded to the enclosure is essential to the safety of an electrical distribution system.


  36. #36
    James Duffin's Avatar
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    Default Re: A question about bonding

    Here is a interesting pdf about grounding...

    Attached Files Attached Files

  37. #37
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    Default Re: A question about bonding

    Thanks James, Roger, HG, and Joe.
    The missing bonding screw was the first thing I saw. then there was the plastic pipe. I've posted another shot of the plastic pipe coming into the basement and attached to the copper pipe with a blue compression fitting.

    Re: the positioning of the meter: the house was built in 1948. People were short, bad diets during the war years. It is a typical installation for the age, and yes, they often leak, but not worthy of mention. The new service mast will be clamped to outside of the wall and the new meter will be at the correct height.

    The red, white and black are taped and abandoned in the corner of the panel. NC.

    I guess I should have called out the red neutral. Next time. []

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    John Kogel, RHI, BC HI Lic #47455
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  38. #38
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    Default Re: A question about bonding

    John,

    Thanks for the special picture file and info .



    Last edited by H.G. Watson, Sr.; 04-26-2011 at 06:30 PM.

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