Entrance wiring

Hello all - I’m in the process of rewiring an old cabin and updating the entry service. I’m going more than 6 feet in the house and therefore am required to have a shut off switch outside. The wiring between the meter base and shut off seem straight forward but I’m required to use a cable with 4 wires between the shut off and the breaker box in the back room. I’ll attach photos but if anyone has insight on where the wire that’s not the two hots or neutral should be terminated on the breaker box and the shut off switch that would be a huge help. Thanks in advance.

Here are some photos of the equipment and cables used with labels to reference

You have a wire missing between the D & E connections. Through the tapped holes wich show up in the picture of the E connection points you will mount a Grounding Busbar. You will also purchase an add on lug for that busbar and the neutral busbar of the first panel; that is the one with the C & D connections shown in it's photograph. Those add on lugs will be sized for the bare wire in the cable. You will run that bare wire from the neutral busbar of the C & D panel to the separate equipment grounding busbar of the E panel. Do not install the bonding screw; which is green in color; in the E panel. The E panel is supplied with a Feeder rather than Service Entry Conductors (SECs). Feeders include an Equipment Grounding Conductor in all cases. Panels supplied by a feeder must keep the EGCs and the neutral conductors entirely separated and insulated from each other. I will have to add pictures later as I am out of time.

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Tom Horne

Thank you so much! Any pictures would be great whenever you get time. I really appreciate it. If I’m understanding you right, the bare (3) and neutral (4) in the feeder wire will be electrically connected on the C and D panel (on the neutral bus bar) but separated on the E panel using the mounted grounding bar? I will update my drawings and repost when I can.
Here’s a sketch let me know if I’m anywhere close.

Your there. Just let me say again that the Equipment Grounding busbar in Panel E will be added by you and that all of the Equipment Grounding Conductors, for all of the circuits that originate from a circuit breaker in that panel, will be terminated on that added busbar. Only Neutral conductors will be terminated on the built in neutral busbar and the green bonding screw which was supplied with Panel E will NOT be installed!

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Tom Horne

One other thing I am not clear about. In your photograph of the meter enclosure I cannot make out if it is installed inside or outside of the building. Most Electrical Utilities will not allow an indoor meter in single family homes. The Utility will also have very specific standards for were and at what height the meter will be mounted. If the meter would be in a portion of the yard that is fenced off from the street that will not be acceptable to many Utilities.

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Tom Horne

A couple of more things.

In panel E it appears that you have the connections mismarked in your photograph. You already know that the bare conductor from the cable terminates on the Equipment Grounding busbar that you will install in that panel. [Select one that has the same or more terminations as the number of breaker slots in that panel.]

Conductor 4 will go on the middle lug which is built into the panel and which has an "N" underneath it.
Conductor 1, which is black without any additional marking, will; by custom; go to the Left hand lug.
Conductor 2, which is black with a Red Stripe, will; by custom; go to the Right hand lug.
Conductor 3 will go to the lug that you will add to the separate Equipment Grounding busbar that you will install. All of those connections will be made immediately after using a wire brush to remove any Aluminum Oxide from the stripped portion of each conductor and applying an Anti Oxidase Paste. Ideal NOALOX and Gardner Bender Ox-Gard are 2 brands of these pastes.

Some will tell you that the Anti Oxidase Paste is not required in some modern panels and they may even be technically correct. Even if the listing and labeling of the panel does not require the Anti Oxidase Paste using it is still good practice and I would not make an Aluminum wire connection without it.

The National Electric Code does not specify which side of the panel that the Black conductor, numbered 1 in your photograph, will supply. Nor does it specify which side of the panel the Black with a red stripe conductor, numbered 2 in your photograph, will supply. That is why I have the phrase; "by custom;" set off in semi-colons.

If you have any more questions please ask.

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Tom Horne

Very good. I cannot express enough gratitude for taking the time to help me.

I won’t insert the bonding screw in the E panel but I should insert the green bonding screw in the C&D panel? (The shut off switch?)

As for the meter base, I haven’t mounted it yet but will be mounting it outside when I’m ready. Thank you for the reminder to check the local height requirement though!

I did miss label the original photos under the assumption the bare wire would be tied together with the neutral. I’ll be running the (4) black with a white stripe wire as a neutral in between panels C&D and E. Again, can’t express how much of a help you’ve been. I plan on gathering the needed materials and finishing the project by next week. I will take pictures and post them if you don’t mind a final critique and hopefully help future DIYers who come across this!

And maybe you can clarify this for me, but what is the reason for keeping the neutral and ground separate in the breaker box?

Humbleabode said:

And maybe you can clarify this for me, but what is the reason for keeping the neutral and ground separate in the breaker box?

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Since many objects that don't normally carry electricity are connected to the Equipment Grounding Conductor (EGC); including the metal parts of handheld tools and appliances; it is important that the EGC not carry normal operating currents the way the Grounded Current Carrying Conductor (Neutral) does. The hazard here is twofold.

First there would be some voltage drop on the EGC. By that I mean that there would be a difference in the voltage between the far end of a circuit and the panel. That can cause current to flow on the metal objects and surfaces that were not meant to carry current. Even under the best of conditions that difference in voltage can be a hazard to the very old and the very young.

In the event of an open in the feeder neutral all of the current of all of the 120 volt loads would be returning to the Equipment Bonding Jumper; which s that green screw that you will put in the Service Entry Enclosure's neutral busbar to bond the enclosure to the Neutral of the Service Entry Conductors; at the panel you are calling the main switch; and back to the utility's transformer via the EGCs, main bonding jumper, and the neutral of the Service Entry Conductors. That would cause a markedly elevated voltage on exposed conductive surfaces that could be dangerous to everyone.

Those 2 scenarios are why the National Electric Code (NEC); of the United States; now requires that the Neutral and the EGC be kept separated from each other so that only the current from a fault will travel on the EGC.

Not so very long ago the NEC allowed the chassis of kitchen ranges, clothes dryers and similar appliances to be bonded to the neutral so that any contact between the Hot and the metal frame would create a short circuit which would open the Over Current Protective Device (OCPD) [Fuse or circuit breaker in homes]. But in some cases the Neutral conductor of such circuits would fail open. In the absence of a separate EGC there is no pathway back to the utility's transformer from which that current originated. That would cause the conductive surfaces of the appliance to rise in voltage to a full 120 volts. So you jump out of the shower,relize you need a piece of clothing that is in the clothes drier, run down to the basement, across the conductive concrete floor, grab the metal handle of the drier, and become the guest of honor at a funeral. That is not far fetched. There are hundreds of documented cases of such electrocutions. That is another reason that the NEC now forbids using the Neutral to ground equipment and requires a separate EGC to all loads that are in dwellings. The exceptions allowed for industrial premises are few and quite unique.

For this purpose any contact between the current carrying conductors, including both the Energized Conductors [Hot] and the Neutral Conductors that connects with the EGC is a Ground Fault. If the accidental contact were between the Energized Conductor and the Neutral that would be a Short Circuit.

I do realize that is a lot to take in. If it raises questions for you just ask. The only stupid question is the one you didn't ask!

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Tom Horne

So this is why I often find that grounding the neutral in a GFCI-protected receptacle will trip the GFCI?

So this is why I often find that grounding the neutral in a GFCI-protected receptacle will trip the GFCI?

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That is what it is supposed to do. A Wiggy; read a Wiggington solenoid voltage tester; draws about 6-7 Milliamperes. The maximum leakage current; read the maximum difference in current between the hot and the neutral; that a 120 volt GFCI is supposed to put up with is <5 Milliamperes. That made me treat the Wiggy as a perfectly adequate GFCI tester in that if I went between the hot and the neutral of a 120 volt GFCI the Wiggy's 7 milliamps of current draw could be expected to trip it. Inspectors always used one of those plug in testers with the precision resistor in them so that it drew exactly 5 milliamperes but I thought the 2 milliamperes higher was close enough. The basic premise is that any significant difference of current flow in the conductors of the circuit means that some of that current is getting back to the source transformer by a route outside the normal current carrying conductors of the circuit. Since it only takes about 30 milliamperes to kill a healthy adult; and less for the very young and the very old; current traveling outside the circuit is a bad thing. That is also why the neutral must not be bonded to ground anywhere but at the Service Disconnecting Means.

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Tom Horne

My point was that even with the neutral connected to ground at the service disconnect, connecting the neutral to ground at a remote receptacle (presumably the remoter the better) will trip the GFCI. That will apparently produce a current flow in the neutral of over 5ma, although one would think a conductor grounded at each end wouldn't have much current flowing.

Michael Armstrong said:

My point was that even with the neutral connected to ground at the service disconnect, connecting the neutral to ground at a remote receptacle (presumably the remoter the better) will trip the GFCI. That will apparently produce a current flow in the neutral of over 5ma, although one would think a conductor grounded at each end wouldn't have much current flowing.

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If there is no current flowing in the energized conductor then faulting the neutral to ground will not trip the GFCI. A GFCI measures the difference between the energized conductor and the neutral. As long as that difference is less than 5 Milliamperes it will stay closed. But if the difference reaches 5 milliamperes the GFCI will open the circuit. With the more recent GFCI designs you cannot close the GFCI circuit unless there is AC voltage present in the circuit. But with no current flowing no difference in current can occur and the GFCI will remain closed.

I first saw this a couple years ago, and found (in http://www.ecmweb.com/content/think-gfci) this:

"...the UL standard requires that GFCIs trip with a 6mA ground fault even when the neutral and ground are connected. To meet this requirement, GFCIs trip when the load side neutral and equipment grounding conductors are joined, even if there is no ground fault."

Michael Armstrong said:

I first saw this a couple years ago, and found (in http://www.ecmweb.com/content/think-gfci) this:

"...the UL standard requires that GFCIs trip with a 6mA ground fault even when the neutral and ground are connected. To meet this requirement, GFCIs trip when the load side neutral and equipment grounding conductors are joined, even if there is no ground fault."

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Great information. I've not been keeping up with the annual technical information reviews since I retired. Thank you.

Michael Armstrong said:

My point was that even with the neutral connected to ground at the service disconnect, connecting the neutral to ground at a remote receptacle (presumably the remoter the better) will trip the GFCI. That will apparently produce a current flow in the neutral of over 5ma, although one would think a conductor grounded at each end wouldn't have much current flowing.

Click to expand...

This is where my thinking got fouled up. I cannot see how the ground fault between the Neutral and the Equipment Grounding Conductor can cause a current flow. If there is already current flowing then such a fault would cause a large enough difference in the current between the energized conductor and the neutral conductor to trip the GFCI. If there is no current flowing there must be some other way of detecting the cross between the neutral and the load side EGC. I wonder how that is done. Do you have any information on how the device detects the fault without having any load current flowing?

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Tom Horne

My only guess right now is that with no load current flowing, ANY neutral current might trip the thing. I tried this today, however, on a new Square D CAFI breaker, and it worked as expected -- i.e., no trip when neutral was grounded at a receptacle. I'll keep looking, and post further if I find enlightenment.

Michael Armstrong said:

My only guess right now is that with no load current flowing, ANY neutral current might trip the thing. I tried this today, however, on a new Square D CAFI breaker, and it worked as expected -- i.e., no trip when neutral was grounded at a receptacle. I'll keep looking, and post further if I find enlightenment.

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Isn't the trip level on a CFI higher than a GFCI breaker at somewhere around 30 Milliamperes? Isn't it only the Dual Function CFI and GFI breakers that have the 5mA trip point? I'm wondering if the higher fault trip point of the CFI breaker as compared with the trip point of a GFCI breaker has something to do with it's detecting a neutral to ground cross. I still haven't found information on the physical mechanism that trips the GFCI Breakers Open on a cross between neutral and the EGC. Since the "CAFI" breaker you mentioned is not listed as a GFCI is it even required to detect a neutral to EGC cross as a GFCI is?

Good question. The CAFI detects and reports (via its internal diagnostics) 6 different faults, including ground faults:

...but its function as a GFCI is questionable, and generally not explicitly mentioned in Schneider's literature. In fact, I was told by a Schneider tech support guy that it was NOT a GFCI. They say: "Breakers designed to protect against parallel and series arcs are called Combination Arc-Fault Circuit Breakers, have a CAFI suffix, and have a white test button. An example catalog number is QO120CAFI." I remain puzzled, but will continue digging in to it as time permits. Somewhere I found a pretty good internal diagram of how a GFCI works, but it's escaped me for now.