Tom.Margillo
Member
Why is it necessary to put a ground loop around a building or structure. 4/0 bare copper around a building with ground rods every 20' then off of every other steel column a 4/0 cad-welded tieing into the loop. 
Grounding loop
- Thread starter Tom.Margillo
- Start date
- Status
bphgravity
Senior Member
- Location
- Florida
Re: Grounding loop
This is called a ground ring or sometimes a ground halo. It may also serve as a counterpoise.
The designer must believe this will provide the system with an effectively low impedance ground for the protection of the service and building against lightning.
Its most likely a big waste of matierlas and labor.
This is called a ground ring or sometimes a ground halo. It may also serve as a counterpoise.
The designer must believe this will provide the system with an effectively low impedance ground for the protection of the service and building against lightning.
Its most likely a big waste of matierlas and labor.
Tom.Margillo
Member
Re: Grounding loop
My thoughts exactly but every job I have worked the last five years had the same thing.
My thoughts exactly but every job I have worked the last five years had the same thing.
Re: Grounding loop
It is called a ground ring, I have specified many of them for telephone companies. They are not a complete waist for places housing communications equipment and incorporating lightning protection system.
Communication facilities have several entry points where cables enter/leave the building and the ring makes it very easy to gain access to earth electrode wherever cables enter/leave the building for termination of the sheaths and cable protectors. A good example would be wave guides, coaxes, fiber cable, and multi-pair cables.
It is called a ground ring, I have specified many of them for telephone companies. They are not a complete waist for places housing communications equipment and incorporating lightning protection system.
Communication facilities have several entry points where cables enter/leave the building and the ring makes it very easy to gain access to earth electrode wherever cables enter/leave the building for termination of the sheaths and cable protectors. A good example would be wave guides, coaxes, fiber cable, and multi-pair cables.
physis
Senior Member
Re: Grounding loop
I'm going to demonstrate my ignorance of lightning protection systems again.
Isn't something like a ring used, with radial wire electrodes extending from the ring outward, for protection of structures that are very susceptable to lightning?
Why would this be a good idea in one case and wasteful in another?
Or do I just not have it right?
I'm going to demonstrate my ignorance of lightning protection systems again.
Isn't something like a ring used, with radial wire electrodes extending from the ring outward, for protection of structures that are very susceptable to lightning?
Why would this be a good idea in one case and wasteful in another?
Or do I just not have it right?
Tom.Margillo
Member
Re: Grounding loop
When I installed Lightning Protection on the same building that had the ground loop,ring,halo it was not permitted to attach to the same loop, a new loop had to be installed the same way the ground loop was. Talk about overkill.
When I installed Lightning Protection on the same building that had the ground loop,ring,halo it was not permitted to attach to the same loop, a new loop had to be installed the same way the ground loop was. Talk about overkill.
Re: Grounding loop
Cellular towers and aircraft hangers have this type of protection. Look at NFPA #780.Originally posted by Tom.Margillo:
Why is it necessary to put a ground loop around a building or structure. 4/0 bare copper around a building with ground rods every 20' then off of every other steel column a 4/0 cad-welded tieing into the loop.
Re: Grounding loop
That is cetainly one way of doing it. Most of my designs that use a ring and have LPS I will take the down conductor to a rod loacted just outside the ring. The rod then will be bonded to the ring and have a radial extended outward from the building. For Towers the will be a ring around the tower and building bonded to together with a ground grid mat made of # 6AWG. On the corners of the building and each tower leg there are radials extending outward.
Tom.Margillo
Member
Re: Grounding loop
Wouldn't there be a risk of sending the lightning back into the building when you bond them together.
Wouldn't there be a risk of sending the lightning back into the building when you bond them together.
Re: Grounding loop
I installed a ring like this and air terminals on a building. The building owner told me that they were requiring it, not for lightning, but for security. This was a high-tech company and they felt that this would help reduce the signals that their computers were putting out and make it more difficult for a foreign agent to see what was going across their internal network. I don't know, it sounded hokey to me, but it paid good!
I installed a ring like this and air terminals on a building. The building owner told me that they were requiring it, not for lightning, but for security. This was a high-tech company and they felt that this would help reduce the signals that their computers were putting out and make it more difficult for a foreign agent to see what was going across their internal network. I don't know, it sounded hokey to me, but it paid good!
Re: Grounding loop
However down conductors and air terminals do not form a RF shield, the spacing is to far apart to do that. Spacing of the grid has to be in fractions of an inch to form a ground plane, not measured in feet. In some cases like Military and RF testing facilities the room is completely enclosed by copper plating to provide maximum shielding and leakage. Not something you really need at your home or business.
Now this is an miss-application. Military facilities that use zone RED areas to house sensitive communications will embed a copper screen (not unlike the window screen on your windows)in the walls and ceiling to form a EMI shield to prevent RF leakage and detection. They shield is then bonded to the ring and all other electrodes.
However down conductors and air terminals do not form a RF shield, the spacing is to far apart to do that. Spacing of the grid has to be in fractions of an inch to form a ground plane, not measured in feet. In some cases like Military and RF testing facilities the room is completely enclosed by copper plating to provide maximum shielding and leakage. Not something you really need at your home or business.
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Grounding loop
What 250.60 says is that you can't use the air terminal conductors and their associated electrodes in lieu of the grounding electrodes that the electrical system requires. You need to satisfy the rules in 250.50 (for creation of a grounding electrode system), separately from what you do with lightning protection.
250.60 says that it does not prohibit you from bonding the building's GES to the lightning protection system's electrodes. What I do not know is what, if anything, requires it. I know that 800, 810, and 820 have rules about bonding the electrodes associated with communication systems to the building GES. What requires the same for the lightning protection system?
- Location
- Massachusetts
Re: Grounding loop
250.50
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
Re: Grounding loop
I don't think so, Bob. It's kind of a "catch 22" situation. 250.50 says that all available electrodes will be part of the GES. But 250.60 says you can't use the lightning protection system's electrodes in lieu of the GES. So where does the GES end and where do the lightning protection system's electrodes begin? Since 250.60 only says that you are not forbidden to bond them, that tells me first the NEC considers them to be separate beasts, and it tells me second that we are not required to bond them. So I don't think 250.50 gets us there.
I don't think so, Bob. It's kind of a "catch 22" situation. 250.50 says that all available electrodes will be part of the GES. But 250.60 says you can't use the lightning protection system's electrodes in lieu of the GES. So where does the GES end and where do the lightning protection system's electrodes begin? Since 250.60 only says that you are not forbidden to bond them, that tells me first the NEC considers them to be separate beasts, and it tells me second that we are not required to bond them. So I don't think 250.50 gets us there.
bphgravity
Senior Member
- Location
- Florida
Re: Grounding loop
Check out 250.106
I don't care how much copper you put in the ground and in what configuration you connect it. There is no absolute guaranty of lightning protection. The best today and for years to come will be TVSS and other surege protection devices.
Check out 250.106
I don't care how much copper you put in the ground and in what configuration you connect it. There is no absolute guaranty of lightning protection. The best today and for years to come will be TVSS and other surege protection devices.
- Location
- Massachusetts
Re: Grounding loop
If the lightning protection system uses electrodes that fit the descriptions in 250.52(A)(1) through (A)(6) then IMO they must be bonded to the service electrodes.
That aside I agree with Byran.
I can not understand your position.
If the lightning protection system uses electrodes that fit the descriptions in 250.52(A)(1) through (A)(6) then IMO they must be bonded to the service electrodes.
That aside I agree with Byran.
Re: Grounding loop
Charlie, I do not have access to 2005 book but do have 2002 with me, unless something changed finnish reading out 250.60.
"This provision shall not prohibit the required bonding together of grounding electrodes of different systems".
Charlie, I do not have access to 2005 book but do have 2002 with me, unless something changed finnish reading out 250.60.
"This provision shall not prohibit the required bonding together of grounding electrodes of different systems".
- Status