Lightning Protection

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Alwayslearningelec

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What determines if a building needs lightning protection. I would imagine the height. But what if you had a building that was 2 stories but with no other buildings around it for say 2-3 miles. Would that qualify for a lightning protection system? Thanks.
 
I am not sure that lightning protection is ever "required" by the code. I am no expert on lightning protection but I have done a few buildings but only in the spec for the job was it required. I do know that you might find some answers in NFPA 780.
 
Nearly every building we do has LP. I know every engineer specs it. If it gets value engineered out of the job, the engineer is off the hook.
Lightning is so unpredictable and doesn't always, or rarely strikes the highest point.
Remember electricity 101 about the least path.
It's really a cheap way to protect your new or older asset, especially when you have invested millions in sensitive equipment like computers, medical equipment, audio/visual, theatrical, generators, roof top HVAC equipment. Not to mention the structure of the building. In the scheme of things, spending an extra $20K for LPS is cheap compared to the other big ticket items on a commercial electrical job.
Florida is the leader in lightning strikes. Texas, LA are close. So down here, it just makes sense.
 
cdslotz is correct. consider the location as well, if electrical storms occur then you might need to consider LP. NFPA 780 will give you guidelines with regards to designing such system.





cdslotz said:
Nearly every building we do has LP. I know every engineer specs it. If it gets value engineered out of the job, the engineer is off the hook.
Lightning is so unpredictable and doesn't always, or rarely strikes the highest point.
Remember electricity 101 about the least path.
It's really a cheap way to protect your new or older asset, especially when you have invested millions in sensitive equipment like computers, medical equipment, audio/visual, theatrical, generators, roof top HVAC equipment. Not to mention the structure of the building. In the scheme of things, spending an extra $20K for LPS is cheap compared to the other big ticket items on a commercial electrical job.
Florida is the leader in lightning strikes. Texas, LA are close. So down here, it just makes sense.
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NFPA 780, ?Standard for the Installation of Lightning Protection,? has your answer. It contains a step-by-step process for determining the degree to which a lightning protection system (LPS) is ?needed.? Actually, the process has two possible outcomes: (1) LPS is recommended, and (2) LPS may be optional. The factors that are considered include,

  • Frequency of lightning strikes in the area (a number taken from a published map),
  • Degree to which the facility is likely to catch fire, if hit by lightning (e.g., materials of construction, types of materials stored inside),
  • Physical size and shape of the facility,
  • Value that is placed on the facility and its contents (i.e., a hospital would have a higher value than a fast food restaurant or a warehouse).

There are other factors as well. Essentially, you are weighing the notions of ?how likely is a lightning strike and how bad would it be? against the notion of ?how much would it hurt if it happens.? I have done this type of analysis a few times. It is not very complex, but it does require some input from the architect and the owner.
 
cdslotz said:
Remember electricity 101 about the least path.
Click to expand...
Please don't. :happysad: In fact, please forget that lesson as quickly as you can. :happyyes: It is a lie, and always has been a lie. :thumbsdown: Electricity takes every path it can find, not just the path of "least resistance." The path that has the lowest resistance will get the most current. But if there is a second path, one with even much, much higher resistance, that second path will get some amount, perhaps a very small amount, of current. And that small amount may be enough to have fatal consequences. :eek:
 
Check your local building code. For instance, the state of Florida mandates the installation of lightning protection systems for Hospitals (419.3.19) & Nursing Homes (420.3.26), no matter the size, location, or other criteria. An NFPA 780 Risk Assessment is required for all public educational facilities, and shall be protected accordingly (423.17.7).

Other public buildings such as, fire / police stations, EOC centers, courthouses, etc. are typically also required to be protected to meet FEMA / ICC certification.

Insurance & underwriting interests may also mandate the installation of an LPS in order to be provided with coverage.

Last but certainly not least, the design professional, developer, and/or building owner may call for the installation of an LPS.
 
charlie b said:
NFPA 780, ?Standard for the Installation of Lightning Protection,? has your answer. It contains a step-by-step process for determining the degree to which a lightning protection system (LPS) is ?needed.? Actually, the process has two possible outcomes: (1) LPS is recommended, and (2) LPS may be optional. The factors that are considered include,

  • Frequency of lightning strikes in the area (a number taken from a published map),
  • Degree to which the facility is likely to catch fire, if hit by lightning (e.g., materials of construction, types of materials stored inside),
  • Physical size and shape of the facility,
  • Value that is placed on the facility and its contents (i.e., a hospital would have a higher value than a fast food restaurant or a warehouse).

There are other factors as well. Essentially, you are weighing the notions of ?how likely is a lightning strike and how bad would it be? against the notion of ?how much would it hurt if it happens.? I have done this type of analysis a few times. It is not very complex, but it does require some input from the architect and the owner.
Click to expand...

Unless Local Code or Insurance requires lightning protection, your are not required to install any. If you CHOSE to do so the use of NFPA 780 is one way to install a system that is compliant with the only recognized lighting Standard in the US. There are literally millions of public and private buildings without lightning protection. My house does not have one and NONE does in the entire town.
 
weressl said:
...If you CHOSE to do so the use of NFPA 780 is one way to install a system that is compliant with the only recognized lighting Standard in the US.
Click to expand...

The NFPA 780 is perhaps the MOST recognized US standard, but certainly not the only one. The LPI 175 is also widely recognized...
 
All you can do with a lightning protection system is improve the reference to earth at certain points on a building or structure.

You will not effect where atmospheric charges will build up, if that charge happens to come close enough to your protection system you have increased the chance that it will discharge through the protection system, but have not guaranteed that it will.
 
kwired said:
All you can do with a lightning protection system is improve the reference to earth at certain points on a building or structure.

You will not effect where atmospheric charges will build up, if that charge happens to come close enough to your protection system you have increased the chance that it will discharge through the protection system, but have not guaranteed that it will.
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Very good summation to keep in mind. No lightning system can GUARANTEE with 100% certainty that the object will not be struck, or induced current will not damage your equipment.
 
weressl said:
Very good summation to keep in mind. No lightning system can GUARANTEE with 100% certainty that the object will not be struck, or induced current will not damage your equipment.
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Maybe not 100%, but cell towers can and do operate with impunity while being struck again and again with lightning. I would give them a 99.999 percent survival rate.

The main issue with lightning protection is the cost of a system stout enough to take multiple, direct hits.

Lighting protection is very important to amateur radio operators. Sure, I can design a tower and protection system that could take direct hits, but the amount of money cost to construct such a system would be many times more than the radios it would be protecting.

I don't know if PolyPhaser has been mentioned, but they have a great site on lightning protection.
 
bphgravity said:
The NFPA 780 is perhaps the MOST recognized US standard, but certainly not the only one. The LPI 175 is also widely recognized...
Click to expand...

If you have a copy of one or the other you are good. I have copies of both and can guarantee you someone did a careful job of plagiarizing the other to cover themselves in copyright laws. They both say the same thing in different words to a tee.
 
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