Here is a link to a useful document on the merits of lightning rods:
http://www.agu.org/focus_group/ASE/NFPAreport.pdf
On the topic of "lighting rods attract (more) lightning and therefore should not be installed" as opined by one or more fire department personnel, I have the following logic to share:
The first part of the assertion is technically true. The higher a conductive object is located, the greater the chance it will be struck by lightning. Raising a conductive object 12" (the typical height of a lightning rod above the protected structure) will infintessimally increase the chance of "attracting" a lightning strike. But the validity of the logic of the complete statement ends there. The object of lightning rods is not to reduce or eliminate lightning strikes. (There are other technologies that strive for that - but they are still in the experimental stage.)
The object of lightning rods is to direct lighting into the ground that would otherwise tend to strike your house. The rod(s) conduct the lighting strike away from the structure of the house, reducing the chance for fire or other damage to the structure caused by the lighting strike. Properly installed lightining rods have proven effective in accomplishing this purpose.
One properly installed rod on a house will not be effective. There needs to be several, optimally not more than 10' to 15' apart from one another or from any other high spot of the roof. The closer they are together, the greater the reduction of chance for the structure being hit. There is a cost-effective point that seems to be in the vicinity of plus or minus 15 feet from one another across the extent of the roof system.
On a related topic, I have a call in to Mike Farrington (referred by Kim in the Ocala Offie) of TECO. Mike is over all the service techs in this area. His number is 352-401-3417. My questions to him will include:
1) Is there any significant difference in level of safety of gas lines installed in the attic compared to ground mounted gas lines in a lightining prone area.
2) What modifications have been made to the gas connections in the attic over the years in The Villages to increase their safety.
3) How can I be sure that my attic gas line installation reflects that latest improvements and safety measures?
4) Are there any measures that can or should be taken by the homeowner to improve the safety of this system, given our lightning-prone environment?
Any other good questions you can think of to ask are invited.
And finally, here are two articles about the attic mounted gas line materials (corregated stainless steel tubing (CSST)) particularly subject to rupture by lightning strikes:
http://www.wthr.com/global/story.asp...e=Printableand http://hawkeyehomeinspects.com/docum...ST-DANGERS.pdf
It appears that this type of material is used in new homes with attic gas line installations in TV. The question is: Is proper grounding sufficient to prevent perforations from electrical discharge from lightning? Or is replacement with black iron pipe or a lightning diversion system safer alternatives?
My admittedly unscientific conclusion after reading the above articles is this:
Grounded or not, CSST serves as an effective lightning-attracting ground - like having a lightning rod in your attic. With the older, thick-walled "black iron" pipe used for gas transmission, a lightning strike does not perforate its thick wall, and the mega volts are conducted harmlessly into the ground. In the case of CSST, a lightning strike will perforate its thin wall as it is conducted disasterously into the ground.
Comments and critiques from you electricians, electro-mechanical engineers, physicists and other logical types out there?
08-11-2008, 10:47 AM
Re: Lightning Protection
