Lightning protection system on building - increased risks

[hansforum]

Hi!

Does lightning protection system on building increase the chances that this building will be hit by a lightning compared to this same building without lightning protection system? Some people say that it does and some that it doesn't. What is correct?

If this is not correct forum to post this can someone recommend where to ask this question?

Thanks!

 

[jghrist]

You can get flashes from the down conductor to grounded objects in the building. That's why there are firmulas im NFPA 780 to determine how large a gap to maintain frin the down conductor.

 

[hansforum]

When I walk on the synthetic carpet in rubber shoes and when I touch metal objects (big metal pot, faucet) there is a spark between my finger and the metal object but when I touch any other non metal object the is no discharge. Why?
If we sad that lightning doesn't care metal or not why this little lightning (static discharge) does?

 

[davidbeach]

There is always a discharge if you touch a surface of lower potential. But, if that other surface is an insulator the rate of discharge is much lower. Find a location where you can be assured of getting a good sharp discharge from a metal door knob or handle on a glass or wood door. Now, under the same circumstances go up to the door, but before touching the metal, touch the door itself; then you can touch the metal without feeling the discharge. The only way that happens is if you do discharge through the insulating material of the door.

 

[Compositepro]

Another factor is capacitance. The larger the metal object, the greater its capacitance (which is the capacity to store charge). Earth is the largest capacitor around and that is why lightning strikes it so often.

 

[hansforum]

But why when I touch the metal object (door knob) I can hear spark between my finger and metal and when I touch glass on the door there is no spark? I know there is greater discharge when I touch metal but why is there a spark before I touch metal and there is no spark before I touch wood? If we observe the wooden door with metal knob, both door and door knob should be at the same potential. Or not? If wooden door and metal knob are at the same potential there should be spark between my fingers and any part of the door no matter metal or not, because spark occurs before touching and it depends on voltage between objects.

 

[Compositepro]

Voltage is required only to initiate the spark. The size of the spark, or brightness is determined by the amount of charge transfer, or current. Wood is basically an insulator, though not a perfect one, and therefore has no capacitance. Air is also an insulator. Do you expect to spark to air?

Simple questions and simple answers will not lead to much understanding. There is a chapter on static electricity in every physics text, and there are free on-line video courses.

 

[corlickmark]

well, this is an interesting question. if you have two house of similar height and one with a lightening protection it has higher probability to get hit. but as it has a safe path for the current there will be no damage. the reason is when the lightening strike it strikes on the higher ground or higher structure. as you make a lightening structure your house will have a lighting rod that will increase your house's height.

 

[jghrist]

as you make a lightening structure your house will have a lighting rod that will increase your house's height.

An 18" air terminal on the roof of a house will not significantly increase the height for lightning stroke probability purposes.

 

[BJC]

IF your building has a UL approved system installed your chance of insurance covering the damage is better. IF you have none and it's in a high strike area it may be less. IF its' a homemade system you may be SOL.