Help me understand the GEC

[brother]

I was just wondering about the size of the GEC(grounding electrode conductor). Why is it that the GEC has to be BIGGER (sized different) than the EGC (equipment grounding conductor)n in houses (dwelling units). Seeing that a water pipe can break and the continuety (sp?) is broken and the electrode is gone. it looks like a we would want a bigger conductor and less resistance to thru the EGC (to the ground rod) rather than to a water pipe.

This is if im understanding a GEC correctly. Thanks for you input.

 

[wbalsam1]

The EGC connects non-current-carrying metal parts to the GEC which in turn connects to the grounding electrodes. Typically the EGC is sized with regard to the equipment it is intended to provide a ground-fault return current path for, and the GEC is contemplated to carry more current at a given moment, such as a fault that would occur relative to several branch circuits at a time, or a feeder fault, or perhaps a lightning strike (questionable)...It stands to reason that this conductor size would be increased with comparison to what an EGC would be expected to carry. The conductor must not be allowed to burn off before the fault has cleared. IMHO. :smile:

 

[Dennis Alwon]

I was just wondering about the size of the GEC(grounding electrode conductor). Why is it that the GEC has to be BIGGER (sized different) than the EGC (equipment grounding conductor)n in houses (dwelling units). Seeing that a water pipe can break and the continuety (sp?) is broken and the electrode is gone. it looks like a we would want a bigger conductor and less resistance to thru the EGC (to the ground rod) rather than to a water pipe.

This is if im understanding a GEC correctly. Thanks for you input.

I think there is some confusion here. The EGC is the wire that travels with your branch circuits to protect any metal parts from being energize. The GEC can be a water pipe if metal and the ground rod is a supplemental GEC not an EGC.

The reason the wire to the ground rod is smaller than the wire to the water pipe is because the ground rod is only as good as a #6 wire and thus you would never have to run a larger conductor. A ground rod is pretty much ineffective.

 

[brother]

I think there is some confusion here. The EGC is the wire that travels with your branch circuits to protect any metal parts from being energize. The GEC can be a water pipe if metal and the ground rod is a supplemental GEC not an EGC.

The reason the wire to the ground rod is smaller than the wire to the water pipe is because the ground rod is only as good as a #6 wire and thus you would never have to run a larger conductor. A ground rod is pretty much ineffective.

that goes to my question, I think that the ground rod WOULD be MORE effective than the water pipe especially in older homes, seeing how the water pipe breaks and sometimes is replaced with plastic(pvc) FOR quick repairs. So this 'SUPPLEMENTAL' GEC (ground rod) is really the only good GEC.

Ive even heard that some plumbers/pipefitters do NOT like us (electricians) bonding to the water pipe for that reason, some claim to have gotten shocked when they went out to an old house to repair/replace the broken pipe that is buried in the ground. Seems like the ground rods can be made bigger and have a bigger wire (#4) go to it than to the water pipe.

love to hear opinions.

 

[tallguy]

I think there is some confusion here. The EGC is the wire that travels with your branch circuits to protect any metal parts from being energize. The GEC can be a water pipe if metal and the ground rod is a supplemental GEC not an EGC.

Huh? I thought the pipe and rod would be called Grounding Electrodes -- GE's if you will, but have never heard anyone put it that way. The Grounding Electrode Conductors (GECs) are what bond them together with the EGCs, etc. Right?

 

[Dennis Alwon]

Huh? I thought the pipe and rod would be called Grounding Electrodes -- GE's if you will, but have never heard anyone put it that way. The Grounding Electrode Conductors (GECs) are what bond them together with the EGCs, etc. Right?

I thought I was saying that the rod and pipe were GE's. i thought the op was calling the egc the wire going to the ground rod but I think I may have misread that.

Yes I agree the gec is a bond. I never thought of it as a bond for the egc although they are tied together.

A service can exist without an egc but it does need the gec. I don't know about ungrounded systems so I am excluding them.

Perhaps we are all saying the same just looking at it from different perspectives.

 

[tallguy]

Perhaps we are all saying the same just looking at it from different perspectives.

Yep, it was just that your acronyms were a bit askew from the norm, that was all.

 

[don_resqcapt19]

that goes to my question, I think that the ground rod WOULD be MORE effective than the water pipe especially in older homes, seeing how the water pipe breaks and sometimes is replaced with plastic(pvc) FOR quick repairs. So this 'SUPPLEMENTAL' GEC (ground rod) is really the only good GEC.

A grounding electrode is not really effective for anything other than lightning or problems caused by accidental contact with a high voltage system. The only play a small part in fault clearing and cannot replace an open service grounded conductor. Now if the electrode is a metal underground water pipe that is common with other buildings in the area it will clear faults and act to serve in place of an open service grounded conductor, but not because it is a better grounding electrode. It can do this because it is really a metallic bonding jumper between the grounded conductor in one building and the grounded conductors in near by buildings.

Ive even heard that some plumbers/pipefitters do NOT like us (electricians) bonding to the water pipe for that reason, some claim to have gotten shocked when they went out to an old house to repair/replace the broken pipe that is buried in the ground.

That is very possible when the service grounded conductor is open or has a high resistance. Also even when the service grounded conductor is intact, the metal water pipe will be carrying some of the grounded conductor current because it is in parallel with the grounded conductor, assuming a common metal underground water piping system. In this case there may be a small arc when the pipe is opened, but there is no shock hazard as the only votlage between the two parts of the piping system is equal to the votlage drop on the service grounded conductor. The voltage drop the service grounded conductor should only be a few volts at most.
[/quote]Seems like the ground rods can be made bigger and have a bigger wire (#4) go to it than to the water pipe.[/quote]
It is unlikely to have a ground rod with a low enough earth resistance to require a conductor larger than what is now required by the code.
Don

 

[Dennis Alwon]

Don can you explain why some people are required to use 10" copper rods 3/4" diameter. Does it really do anything more than the standard 5/8 rod or are they kidding themselves. I am not talking about soil conditions in which copper would do better.

 

[iwire]

why some people are required to use 10" copper rods 3/4" diameter.

Around here that is a typical power company requirement around transformer pads.

Four 3/4" x 10' rods, with one placed about 18" off the four corners of the pad.

They are then connected in a ring with 4/0 CU bare with a 4/0 bare lead cad welded on each side of the pad and brought into the wiring compartment.

Keep in mind that at the voltages the power company is dealing with ground rods do become effective fault clearing paths. I also imagine the use of 4/0 is more for it's physical strength then it's ampacity.

 

[Dennis Alwon]

Thanks Bob-- I had just met a guy who says all his commercial jobs require 2 copper 10' 3/4 rods at the service. Was curious.

Would these rods be beneficial on a residence. I would assume not or they would be required by the NEC.

 

[roger]

Would these rods be beneficial on a residence.

Dennis, for this to be beneficial to a residential service, the voltage to the dwelling would have to be at least 12,470 or more. :wink:

Roger

 

[Dennis Alwon]

Dennis, for this to be beneficial to a residential service, the voltage to the dwelling would have to be at least 12,470 or more. :wink:

Roger

Wow. Guess I don't need copper rods. Thanks Roger.

 

[don_resqcapt19]

Dennis,

Don can you explain why some people are required to use 10" copper rods 3/4" diameter. Does it really do anything more than the standard 5/8 rod or are they kidding themselves. I am not talking about soil conditions in which copper would do better.

There is a small improvement in the resistance to earth both when you increase the diameter or the length of the ground rod. This is often in the job specs.
Don