# Confused about Lightning Ground and Building Ground



## ponders (Aug 25, 2011)

I am currently caught in between 2 difference schools of thoughts regarding if Lightning ground should be bonded to Building's bond, the scenarios are explained below and would like an explanation of basis why there are differing standards existing.

I have just been appointed to oversee Fiber Optics and Networking cables laying project at my workplace

All laying has now been completed and the Contractor is now seeking payment. However during the audit, we have differences in opinions as to whether the groundings should be bonded.

I am currently in Indonesia where Electrical Codes and Standards are just guidelines (not law) and rarely adhered to. Different "_experts_" i spoke to have very different opinions. As the project leader, I need to be sure what the Contractor did was sound before payment is done. I would like to seek answers because even google give conflicting answers.

Indonesia national electrical code is last updated in 2000 and is based on NEC. here are the versions of interpretation I encountered.

*Version 1* (Contractor's Version based on IEC 1024) 
says the Server room's grounding system (2.5 ohm) has to be bonded to Lightning protection's ground (3.5 ohm). Building electrical ground is currently bonded to Server's ground.

*Version 2* (Building inspector based in Singapore, and a British electrical engineer graduate based in Indonesia)
says that lightning protection's ground must be stand-alone from other grounding electrodes. Building and communications ground can be bonded together but not to Lightning's ground. 

there can be a few and bonded lightning electrodes so long they are no where near non-lightning grounding electrode.

*Version 3* (my google research)
NEC 250.50, 250.60 and 250.106 seems to be in conflict with one another.

This is what i got from http://ecmweb.com/grounding/electric_grounding_vs_bonding_10/

"bond this system to the building (or structure) grounding electrode system [250.106]. Do not use the grounding electrode for a lightning protection system as the building (or structure) grounding electrode (250.60)."

from http://www.ecmag.com/?articleID=11248&fa=article

"*Earth-grounding electrodes* Down conductors must be connected to earth-grounding electrodes that are dedicated to the lightning protection system. In other words, the grounding-electrode system for the service equipment for the facility, as well as that used for grounding telecommunications and cable television systems, must not be used in lieu of lightning protection electrode"

and from http://ecmweb.com/grounding/electric_grounding_vs_bonding_6/

"If you use a grounding electrode for a lightning protection system, you can't use it as a grounding electrode for the structure grounding electrode (earthing) system required by 250.50. The purpose of a lightning protection system installed per NFPA 780 is to protect the structure from lightning damage. The concern that bonding the lightning protection system to the building grounding system may create a path for lightning into the electrical wiring or equipment within the structure doesn't justify keeping the two systems separate; separation creates a dangerous potential between them. You must bond your lightning protection electrode system to the structure grounding electrode (earthing) system (250.106)."


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## Jlarson (Jun 28, 2009)

So basically you have your electrical system ground (connecting the neutral point of the electrical service to earth), your lightning protection system ground (connecting all the down conductors to earth) and your telecommunication ground (wire from the electrical grounding electrode(s) to a bar in the telecom room probably in your case) right? 

Even if you do separate electrode(s) for each in the end you need to bond them all together in the end so it's really gonna be one electrode system.


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## ponders (Aug 25, 2011)

Yes, and thanks for the reply.

The primary concern here if there should even be a bond between the Lightning protection system with the Building/Communications grounding system.

Camp 1 says yes to even out the potential differences should there be a sudden surge or lightning strike.

Camp 2 says no because it will risk Electronics and Communications within the buildings from the lightning strike. 

Camp 2 agrees with camp 1 that potential difference should be eliminated but at the same time point out the risk of linking LPS to building's ground is too great.

So me being caught in between am not sure who is correct as Camp 1 and Camp 2 seems to explain their thoughts logically. And things I read on google is conflicting too.


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## Jlarson (Jun 28, 2009)

The main reasons for toeing them together is eliminating the potential difference and as the same time eliminating or at least reducing the potential for side flashes when your LPS (lightning protection system) conductors get near a metal object in the electrical system. 

Think of it this way if a down conductor runs near lets say a metal junction box or conduit and the LPS isn't bonded to the electrical ground there will be a potential difference and the chance for a side flash to that object. 

Actually the same goes for any metal object near the LPS conductors. They will need to be bonded too.


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## ponders (Aug 25, 2011)

K, i am understanding it better now.

My Server/building electrical ground electrode is around 120 feet away from the Lightning one. Basically they are at opposite ends of the building.

The Lightning protection system is somewhat isolated from anything metallic or another circuit. 3 rods on the roof, and down conductors to ground electrode, along the path there is nothing metallic within 20 ft, the only thing i can think of are rebar-rods implanted into the building that might be inches away from the down conductors.

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That being said, how is the Building/Server side of things protected should there be a lightning strike and the LPS are toe-ed in together?

Or due to path of less resistance the lighting current is "in theory" flowing to the ground electrode and not upwards to the server/building. Am i thinking right?

FYI, there are Distribution panel mounted Surge protectors installed for the Server.

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## Jlarson (Jun 28, 2009)

ponders said:


> My Server/building electrical ground electrode is around 120 feet away from the Lightning one. Basically they are at opposite ends of the building.


Still gonna want to bond them, if anything 120 feet of copper burred will make an fairly good electrode. 



> That being said, how is the Building/Server side of things protected should there be a lightning strike and the LPS are toe-ed in together?


Through your surge protection and proper cable shielding, isolation and such. And proper bonding in the telecom room. 



> Or due to path of less resistance the lighting current is "in theory" flowing to the ground electrode and not upwards to the server/building. Am i thinking right?


It's gonna take all available paths. But if everything is done properly your equipment shouldn't suffer, obviously there is always a chance a strike will do damage regardless of what you have in place.


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## ponders (Aug 25, 2011)

Its clear now !

So in a way Camp 1 guys eliminate the risk of surge by protecting the entire circuitry when LPS is bonded.

Camp 2 guys (who might be wrong) are just not comfortable with the risk and isolate both Systems from one another.

Thanks for the helpful reply.


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## Jlarson (Jun 28, 2009)

ponders said:


> Camp 2 guys


Yeah I don't know where they came up with keeping them separate. I have never seen a reputable paper or association suggest that. Never done it in one of my installs either.


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## ponders (Aug 25, 2011)

Well I am wondering because they are basing on a different standards. 

Camp 2 people i have asked are Building Inspectors, Facilities Managers and Electrical Engineer. The common thing between these 3 people is that they received their training either in UK or Singapore (where standards are British based). 

Just wondering, but still Science is Science so standards around the world should be the same.


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## dogleg (Dec 22, 2008)

*dogleg*

I agree nowhere I've read tells me to separate the two .However it does lead right into the grounds of the more sensitive electronic componets .For a while we were losing a card everytime we had lightning strike closebyI could not find any blown "gas block fuses" The phone system is conected to a UPS with surge protection.The only way I could figure out it was coming in was maybe from the ground wires . There is a main grounding grid of 1/0 cu and plenty of steel structures that are bonded together to form a gounding electrode system which in turn is tied together with all grounds including the phone system.Does this theory make any sense?:001_huh:


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## jwjrw (Jan 14, 2010)

Jlarson said:


> The main reasons for toeing them together is eliminating the potential difference and as the same time eliminating or at least reducing the potential for side flashes when your LPS (lightning protection system) conductors get near a metal object in the electrical system.
> 
> Think of it this way if a down conductor runs near lets say a metal junction box or conduit and the LPS isn't bonded to the electrical ground there will be a potential difference and the chance for a side flash to that object.
> 
> Actually the same goes for any metal object near the LPS conductors. They will need to be bonded too.



Where is the roofer from AZ and what have you done with him?.....
That post was way to smart sounding and correct to come from jlarson...:laughing:


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## brian john (Mar 11, 2007)

There is NO way not to have them connected, either you attempt to connect them in a controlled fashion or they are connected through all metallic components in the structure, rebar, metal ducts, water pipes, electrical conduit.

Either way, both ways they are connected.


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## Jlarson (Jun 28, 2009)

brian john said:


> There is NO way not to have them connected


You'd think but some of the well sites and such I've overhauled they were isolated. Why the hell they did it is beyond me. Probably didn't know any better. 

On one the ground bus was mounted on wood and all the conductors where insulated and the electrical stuff was on the wood too. Quick piece of copper and a new ground plate to replace a melted rod for the LPS and all was well.


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## brian john (Mar 11, 2007)

Jlarson,

In some specific structures it is possible to have two systems but in a typical facility with either steel or concrete isolation is next to impossible.

Additionally when lighting strikes a site that has obtained isolation in some mistaken attempt at keeping it clean, the earth can be the connection as the voltage reaches a level to conduct through the ground.


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## Jlarson (Jun 28, 2009)

brian john said:


> Jlarson,
> 
> In some specific structures it is possible to have two systems but in a typical facility with either steel or concrete isolation is next to impossible.


Yeah I agree there, most well shacks here are wood or fiberglass. Guess I should just be happy they got as far as putting in electrodes, that's a big step for some, maybe eventually they'll pick up on the bonding thing. 

Peter, teach your comrades better. :laughing:


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## jwjrw (Jan 14, 2010)

jwjrw said:


> Where is the roofer from AZ and what have you done with him?.....
> That post was way to smart sounding and correct to come from jlarson...:laughing:



Another spot on thankless post........


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## EJPHI (May 7, 2008)

Lots of really good advice here.

I would only add:

1) Ideally all facilities would enter at the same point so that potential differences would be minimized. Real world often does not cooperate though.

2) It is preferred to run the grounding conductor along with the line/signal conductors to reduce the voltage potential difference caused by the lightning strike.

3) Check out http://groups.yahoo.com/group/LightningProtection
Some real pros hang out there and they are good at answering questions. In fact, many of the guys on that forum are from SE Asia.

EJPHI


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## nitro71 (Sep 17, 2009)

I would also post this over on Mike Holt's forum. A lot more engineers there. On a average size building in the US they are bonded together. Say on a high rise I'm not really sure if they do get bonded together. How about a cell tower? Anyone do one of those?


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## Jlarson (Jun 28, 2009)

nitro71 said:


> ....tower?


Every tower we do EVERYTHING is bonded together. We even put a bond strap on the broadcast engineer's metal pen :jester:


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