Lightning Damage to Concrete Encased Electrodes

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I already know about the quality and practicality of concrete encased electrode. I have not read or heard anything about what damage, if any,
is done to the foundation of a building after receiving a lightning strike.
Will the concrete and or the electrode be damaged to any significant degree?
 

George Stolz

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Windsor, CO NEC: 2017
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I would think the answer to that question involves too many variables to give an answer.

How about, "Has anyone ever seen damage to a CEE after a lightning strike?" :)
 

bphgravity

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Location
Florida
Check out these topics:

http://forums.mikeholt.com/showthread.php?t=111891&highlight=lightning+concrete

http://forums.mikeholt.com/showthread.php?t=110796&highlight=lightning+concrete


When it comes to lightning, I think just about anything is possble. I know there is not overwhelming evidence of this being a serious, repeatable, or issue of consideration when designing the grounding electrode system for a building's service.

The fact is that potential damage from lightning is not allowance to not bond a concrete encased electrode as required by code. If the risk of lightning is great, an LPS should be consdiered to mitigate the effects of a near by or direct lightning strike.
 

tesi1

Member
Location
florida
concrete electrodes

concrete electrodes

it has been my experience when using ufer or concrete encased grounding
electrodes you also better have a very low resistance tested ground rod to handle the lightining strike discharges, or you will get the blown out concrete.!
 

dicklaxt

Senior Member
Yes it can do quite a bit of damage to concrete on a building structure I cannot address the foundation as conditions are different.Lets talk about the downcomer,that is the cable from the air terminal network on the roof that goes over the roof edge and or parapet(I think thats the right word,anyway the decorative edge if concrete,LOL).There is a minimum bending radius required on the cable as it transitions from horizontal to vertical over the edge and if it is to tight of a bend the energy will jump(or could) from the horizontal to the vertical cable going thru the concrete and will actually blow a good sized chunk of conrete away.

I suppose if the foundation and downcomer were to mimic this situation it would also or could do similar damage.

dick
 

dereckbc

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Plano, TX
I can tell you from personal experience it can happen, although the circumstances are a bit unique to my field, telecom. It has been several years and I have long since lost the photographs but can remember the details quite well.

All 3 sites were built using the exact same specifications where a #4 AWG wire was just laid in the concrete slab. Basically done to minimum NEC requirements. These were all fiber optic regenerator sites that use 345 KV transmission lines static wire as the carrier for the optic cable. As the cable entered the building, the cable sheath was bonded to the very nearby site ground bar. From the ground bar went into the concrete via #4 AWG conductor.

Anyway when the tower was struck, lighting followed the cable and discharged through the Ufer ground. At the point of entry into the concrete and around the GEC, water vapor in the concrete heated up, turned to steam, and literally caused the concrete to explode where the cable entered the concrete. In one of the shelters it literally cracked the whole corner of the foundation off from the pad.

Lesson learned was exceed NEC minimum requirement, have the re-bar bonded using twist wire or even better Burndy clamps and bond GEC to the re-bar as it will dissipate the heat over a much larger area.

What was really ironic was all three of these sites were on the same fiber route (WDC to Miami) and happened in the same spring season, All the shelters on that route were cookie cutter, but built by various contractors along the route with identical spec. The fix was simple but expensive. We added a ground ring. Problem has never came back to my knowledge.
 
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dereckbc

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it has been my experience when using ufer or concrete encased grounding
electrodes you also better have a very low resistance tested ground rod to handle the lightning strike discharges, or you will get the blown out concrete.!
I am not so sure about that unless you are talking about just doing the minimum NEC requirement of 20 feet of cable in the concrete form,. That was my experience.

If you use some of the methods Herbert Ufer used, or as recommended in some of Poly Phaser guidelines blowout is not a problem because impedance is extremely low and dissipated over a huge area. I mean the bomb shelters Herbet Ufer's designed have never had a single incident, and neither have I since I learned my lesson the hard way.
 
I already know about the quality and practicality of concrete encased electrode. I have not read or heard anything about what damage, if any,
is done to the foundation of a building after receiving a lightning strike.
Will the concrete and or the electrode be damaged to any significant degree?
Just to clarify: the concrete damages are similar to the effect when lightning strikes a live tree. It is the rapidly heated water content that turns into steam that causes the 'explosion' of the tree and the concrete as well.
 

renosteinke

Senior Member
Location
NE Arkansas
While Mr. Ufer gets all the credit for inventing the concrete encased electrode, at least half the credit belongs to Reno electrical contractor Bruce McCain (IIRC).

Bruce was the guy who got it into the NEC. He did so by documenting the performance of the many such electrodes he had installed on ski-lift stations in the Sierra Nevada mountains. His electrodes endured many, many lightning strikes without problems- to either the electrode or the surrounding concrete.

Sure, there are many variables. What's pretty clear, though, is that however much a Ufer might be damaged, any other form of electrode would be damaged far more. Every bit of data collected on the Ufer so far has pointed to this method being many, many times a better electrode than any other method.
 

StephenSDH

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Location
Allentown, PA
Don't mean to hijack a tread, but I assume copper water pipes would also be damaged during a lightning strike for the same reasons. Has anyone seen this?
 

don_resqcapt19

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Illinois
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retired electrician
Don't mean to hijack a tread, but I assume copper water pipes would also be damaged during a lightning strike for the same reasons. Has anyone seen this?
I would not expect damage to the water pipes. Even if you heat the water enough to turn it to steam, that would just increase the pressure of the complete water piping system. I think it would be a rare case where you would have enough pressure to cause damage, with the exception of a length of pipe that has closed valves at both ends.
 
I would not expect damage to the water pipes. Even if you heat the water enough to turn it to steam, that would just increase the pressure of the complete water piping system. I think it would be a rare case where you would have enough pressure to cause damage, with the exception of a length of pipe that has closed valves at both ends.

Also, the water pipes in ground travel for such a long distance, the strike will dissipate over the distance.


The installers who live in lightning prone areas may have some concern, but there are expansive areas of the country that do not see much of lightning striking the service of a building/structure.
95% (I am guessing at this percentage) of the strikes in the Northeast that actually hit a house/structure, hit the roof or siding and completely miss the service. (I am not counting the tall buildings such as in the cities)
 

dereckbc

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While Mr. Ufer gets all the credit for inventing the concrete encased electrode, at least half the credit belongs to Reno electrical contractor Bruce McCain (IIRC).
When was Mr. McCain born and what year did he introduce the CCE to NEC?

Ufer Ground, and CCE and not the same thing.
 

dereckbc

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Location
Plano, TX
Please elaborate
The main difference is the NEC uses bare copper wire embedded into the concrete and no requirement for the reinforcing bar to be used. Where as the Ufer Ground does not use copper wire embedded in the concrete and requires the reinforcing bar to be used.

Copper wire does not react well to the pH factor of concrete as it chips and flakes. The use of steel reinforcement works well and concrete does not chip or flake as has been found with copper. The use of copper wire tied to the reinforcement rods outside the concrete shows none of these problems.
 

don_resqcapt19

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Location
Illinois
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retired electrician
Dereck,
Didn't you also find that with pole foundations, that you had little or no damage where you had the re-bar "double tied" or welded in place of the standard single tie?
 

dereckbc

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Location
Plano, TX
Dereck,
Didn't you also find that with pole foundations, that you had little or no damage where you had the re-bar "double tied" or welded in place of the standard single tie?
Yes Don but the caveat here is POLE FOUNDATIONS because the amount of concrete is so small in comparison to say a slab on grade building the extra cost of double tied are justified for the extra protection it offers.

When you get into regular sized buildings due to the scale of and number of interconnections there is no real benefit IMO to double tie or spot weld. It has been my experience with a foundation as small as say a average size home, just using single tie method can result impedance as low as 1 ohm.

But as I get older and wiser, I am less convinced that such low impedance is of any real benefit. In fact I can make a good argument having such a low impedance can actually cause some problems like high GEC return current as experienced in the ole days of a metallic water pipe system.

What is important in lightning dissipation is not the actual impedance, but rather a number of paths to reduce capacitance and inductive choking. Think if a single or two ground rod system as being a funnel with respect to lightning where the flow gets backed up at the Bottle Neck of the funnel.

Today I build mostly cell tower sites and switch centers, and with the methods we use lightning problems are non existent, or when they do cause damage is minor and usually results from loose connections. A tower site uses a lot of radials, rods, Ufer, grids, and rings, so lightning has a lot of paths to dissipate very quickly before voltage can build up to dangerous levels. Plus the techniques we use inside the shelters also contribute to the effectiveness, but that is another thread, or I should say book. :grin:
 

renosteinke

Senior Member
Location
NE Arkansas
I detect a certain amount of scepticism - which is no surprise, as Mr. McCain's contribution has long been overlooked.

While there is no doubt that Mr. Ufer invented the grounding electrode that bears his name, the method was not accepted into the NEC until the mid-60's. It was accepted at that time solely because of McCain's documentation of the performance of the method- both in general, and as regards lightning strikes.

Let's face it ... you place a steel tower atop a mountain that divides a continent, and you're going to have a perfect lightning target. The "Ufer" grounds performed far better than anyone had expected - and far better than any other method!
 
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