Choking the GEC

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karl riley

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Here's a suggestion for keeping most of the neutral return current on the service neutral instead of on the water service pipe:

This was suggested by one Ed Maxey in an email to Roy L. Beavers:

Take the grounding electrode conductor going to the water pipe and wrap it 11 - 13 turns around a laminated silicon core, such as from an old transformer. How much of the neutral current this will choke off is not stated.

Question: does this violate NEC? Opinions?

I am going to try an experiment. I will take a zip cord, add a paralleled length of zip conductor to the neutral conductor of the cord, use a lamp as the load, and see how much neutral goes in each paralled conductor.

Karl
 
Re: Choking the GEC

P.S. I forgot to say that I will wrap 12 turns of the paralleled conductor around some core material I have.
Karl
 
Re: Choking the GEC

Karl, what you are doing is called girdling or choking a single conductor. IMHO you would be violating the intent of 250.64(E) by intentionally adding unnecessary impedance.

It could completely defeat the purpose of a planned low impedance path for lightning, and accidental contact with MV/HV systems. These type of faults could seek other paths rather than the GEC which is it's purpose in life.
 
Re: Choking the GEC

Originally posted by pierre:
[QB] Adding a resistor to the GEC is permitted./QB]
Click to expand...
Where is it permitted?
You can add a resistor in SDS sytemms between the Xo and GES to limit fault current, but not add a resistor to the GEC conductor.
 
Re: Choking the GEC

Why not cut the water pipe outside the building and insert a non-metallic section. This is both safe and legal. Of course the water piping in the house still needs a bonding connection per 250.104
 
Re: Choking the GEC

Tom, that is my approach. It is the only action which really solves the problem and is allowed by Code (10' out from the building).

Dereck, that was my thought, that since the GEC is primarily for lightning and surge, and since we are asked to keep the runs as straight as possible, a coil would obviously be an obstruction.

It would be interesting to know exactly what would be the effect on a high voltage surge. I know one thing, if it followed the turns of the coil, there would be one heck of a magnetic field pulse shooting out from the coil.

I tried it with a zip cord, but I guess my core material was not very good, since I saw little effect. I no longer have the lab set up I used to have when producing gaussmeters.

But the question remains, aside from intent, does it violate the NEC as now written?

Karl
 
Re: Choking the GEC

I think that the inductive reactance caused by the choke will be minimal at the low current levels that are normally found on the water pipe, but it would be a major impedance to high current flows.
Don
 
Re: Choking the GEC

Originally posted by don_resqcapt19:
I think that the inductive reactance caused by the choke will be minimal at the low current levels that are normally found on the water pipe,
Click to expand...
Inductive reactance is a function of frequency not current.
 
Re: Choking the GEC

Hello Derek
The systems I was alluding to are systems that are not solidly grounded where grounding is not permitted or would cause greater harm. These would be Reactance grounded, resistance grounded or high resistance grounded systems; not your typical residential or commercial systems.
 
Re: Choking the GEC

Originally posted by pierre:
Hello Derek
These would be Reactance grounded, resistance grounded or high resistance grounded systems;
Click to expand...
Pierre, I am familar with the systems and I think my point is still valid. The reactance/resistance is installed between the Xo and ground electrode to limit fault current in a L-N faultand/or prevent the line from tripping from a L-N fault.

I guess it just depends on your point of view. I do not see that adding any impedance to the GES, all the equipment grounds still are solidly bonded without any added impedance.
 
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