EGC / GEC

[Marc M]

Hey Jerry, can the same conductor be used for or act as both the equipment grounding conductor (EGC) and grounding electrode conductor (GEC)?
Example: conductor from the panel's ground bus to the water supply entering the house.
Can you explain the difference between conductor and electrode in how they are used?
Thanks
Marc

[Jerry Peck - Codeman]

Marc,

Depends ...

If the metal water pipe is going into the ground and more than 10 feet of it is in the ground and in direct contact with earth, then that water pipe may serve as a grounding electrode.

If such a case, the conductor going to the water pipe (grounding electrode) is the grounding electrode conductor. Likewise, that same conductor is bonding that same metal water piping back to the service equipment, and the key to that same conductor being able to be used for that same purpose is that the metal water piping which continues to the interior of the building is not broken or made discontinuous by any means, including a water meter.

If there is a water meter installed in the piping, a bond conductor needs to be installed to jump around the meter so that in case the water meter is removed the electrical connection is not broken by the removal of the meter (plumbers have been shocked and some electrocuted by removing a water meter which was serving as a fault-current path and they became the fault-current path when they disconnected the meter). That bonding jumper would need to either continue back outside to the grounding electrode conductor or (more likely) be a separate conductor used to bond the interior metal water piping and the bonding conductor would then run to the service equipment.

Thus, the answer is that, under one special condition, yes, the grounding electrode conductor could also be the interior metal water piping bonding jumper. However, your question was could it also be an equipment grounding conductor, not an interior metal water piping bonding conductor, so the answer to the grounding electrode conductor also being used as an equipment grounding conductor is 'no'.

The grounding electrode conductor specifically connects the service equipment to the grounding electrode system. The reason for this is to help protect the electrical service equipment and electrical system from a lightning strike - that is the reason for the grounding electrode system.

The interior metal water piping bonding conductor is to make a ground path back to the service equipment in case there is a fault-current on the interior metal water piping system. A high enough fault-current and the breaker will trip, By bonding the interior metal water piping back to the service equipment ground, the voltage on the interior metal water piping is keep as close to zero in relation to ground as possible (the interior metal water pipe is like a long resistor, as such, with current flow, there will be a voltage drop across the pipe based on the amperage of the fault-current and the length (resistance) of the pipe. By starting out a zero volts at the service equipment, the voltage drop across the pipe should be able to be kept quite low, unless there is a very high fault-current, in which case the voltage is created by that high fault-current through that resistor (the pipe).

You mentioned equipment grounding conductor, though, and not interior water piping bonding conductor. The equipment grounding conductor is also tied back to ground at the service equipment and is not intended to carry current (no intentional current). The equipment grounding conductor may, though, be carrying some unintentional current (fault-current) due to a ground-fault at some location. The equipment grounding conductor is run with the circuit conductors and is intended to be there as a safety conductor in case there is a ground-fault at any equipment which is connected to the electrical system - plugged in or permanently wired in.

Not sure if that answered your question fully?

The main potential problem I see with the grounding electrode conductor in your photo is that it is in a metal conduit (flexible metal conduit at that, which makes it potentially even worse). The grounding electrode conductor needs to be bonded to that metal conduit at each end of the metal conduit. The problem with using flexible metal conduit is that it is spiral wound and the actual length of the metal is far greater than the length of the flexible metal conduit, additionally, the spiral winding of the flexible metal conduit could, at higher fault-currents, create a choke coil around the grounding electrode conductor inside the flexible metal conduit. With high current flowing spirally around the grounding electrode conductor a magnetic field is produced, and the magnetic field will create an inductive reactance and resistance on the current flowing through the grounding electrode conductor, the right current can create a magnetic field which stops the flow of current through the grounding electrode conductor, which is not a desirable outcome - if there is a fault-current, that fault-current needs to be able to flow unrestricted through that grounding electrode conductor to the grounding electrode system.

Jerry

[Marc M]

Excellent. Couple things.
First, I was incorrect in my question. I was always under the assumption that the EGC was also the method used to bond water pipes.
In swimming pool applications I understand the EGC concept completely.

Okay that said, my question should have been, " can the GEC also be used as the bonding conductor? I need to get the terminology correct because obviously, the individual I learned from was also incorrect in the use of his terminology.
So, if you would be so kind, I'd like to get this straight once and for all.
GEC: Grounds the electrical system as we know it.
EGC: bonds Electrical equipment to all metal parts ( in whatever given area) e.g. Hydromassage tub motor to pipes...
NAME ? : That bonds the equipment panel to water pipes

I attached another image. Same thing, there was no water pipe bond within the interior anywhere. So I assume the GEC is also being used as the water pipe bonding? I noticed it is continuous from the panel, through the electrode (rod) and to the water pipe (electrode).
I know about the conduit being bonded at both ends, I was fascinated to learn about the spiral conduit and how it affects the process.
In this image, can the metal straps at the ends of the FMC make an effective bond?

[Jerry Peck - Codeman]

GEC: Grounds the electrical system as we know it.

GEC=Grounding Electrode Conductor
Yes, sort of, the GEC is the conductor which bonds (connects) the electrical service equipment, the metallic enclosures, the neutral conductor, and the equipment grounding conductors to the Grounding Electrode System. In that sense, because all those things are bonded together at the service equipment, it therefore bonds all those items to the grounding electrode system.

EGC: bonds Electrical equipment to all metal parts ( in whatever given area) e.g. Hydromassage tub motor to pipes...

EGC = Equipment Grounding Conductor
Correct to a point - the equipment grounding conductor grounds the pump and other related electrical items (metal timer enclosures, metal heat pump cabinets, etc.,) back to the service equipment point where the equipment grounding conductor is bonded to "ground", i.e., the neutral and the grounding electrode conductor, and to the grounding electrode system.

The conductor which "bonds" the hydromassage motor to the metal water piping is a "bonding conductor", not a "grounding conductor" as that conductor does not go to "ground", all that bonding conductor does is electrically connect specific metallic items to each other. Now, those metallic items may also be bonded back to ground by means of some other conductor, such as the metal water piping would be bonded back to ground by the interior metal water piping bonding conductor and the metallic pump motor housing would be connected back to ground by its equipment grounding conductor.

NAME ? : That bonds the equipment panel to water pipes

That is typically called a bonding conductor, however, the NEC defines that as a "bonding jumper".
- Bonding Jumper. A reliable conductor to ensure the required electrical conductivity between metal parts required to be electrically connected.

People tend to think of a "jumper" as being short in length, measured in 'inches' instead of 'feet', but there is no maximum length for a "jumper", so people tend to call long lengths of a 'jumper' a 'conductor' instead - makes it more understandable to think of a long 'bonding jumper' as a 'bonding conductor' because there is no mental thought or picture of a short length. This 'short length' aspect possibly comes from seeing the short 'bonding jumpers' in service equipment where the neutral terminal bar is bonded to the enclosure, which is 'grounded' - that 'jumper' is what, maybe 2 inches to 3 inches long?

I attached another image. Same thing, there was no water pipe bond within the interior anywhere. So I assume the GEC is also being used as the water pipe bonding? I noticed it is continuous from the panel, through the electrode (rod) and to the water pipe (electrode).

That would not be the bonding for the interior water piping system, that would be a grounding electrode bonding jumper which is connecting the underground metal water piping serving as the grounding electrode to the supplemental ground rod so that the two different grounding electrodes are 'bonded' together.

Now, *IF* ... that big "if" the metal water piping is unbroken through to the interior of the building and to the interior metal water piping system, that may serve as the 'interior metal water piping bonding jumper', however, there are many AHJ which will require the interior metal water piping' to be bonded to the service equipment with the connection made on the interior side of the piping, after all, that bonding jumper is for the "interior" metal water piping, not the "exterior" metal water piping, and they want to make sure that no repair of the piping, such as inserting a piece of PVC in the outdoor piping, breaks the continuity of the bonding from the "interior" metal water piping.

That is why, in my previous response, I said: "Thus, the answer is that, under one special condition, yes, the grounding electrode conductor could also be the interior metal water piping bonding jumper.", with the critical word there being "could", as in "could also be the interior metal water piping bonding jumper" - that would be up to the AHJ as they 'may not allow that use'.

In this image, can the metal straps at the ends of the FMC make an effective bond?

From the photos it is difficult to tell, but those fittings may well be designed and listed for that purpose. That said, keep in mind that the Flexible Metal Conduit is only there to protect the grounding electrode conductor from physical damage, and that flexible metal conduit is one of the options listed for that protection "it shall be in rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, electrical metallic tubing, or cable armor." I would say that flexible metal conduit is essentially similar to 'cable armor'.

[Marc M]

Very well stated Jerry. This helps to understand the differences between grounding and bonding, conductors and electrodes (and yes, jumpers). I appreciate you taking the time and having the patience to articulate this and clarify if for me.
Much appreciated.