Online Lightning Risk Assessment

[bphgravity]

go here: http://www.harger.com/lightningprotection.htm

Click on "Risk Assessment".

Select one of the two categories.

Enter the required data.

Click on Calculate and the program will indicate wheter or not a LPS is needed.

 

[infinity]

Excellent link. I ran a test model of my own home and was surprised at the result. It assessed my risk at medium.

Bryan, what is your opinion of the validity of this calculation given that these guys are selling lightning protection equipment.

 

[edamico11]

I

I

like the link,,

did my home low

Did the shop,,, well I think I will be leaving now..

 

[tallgirl]

They didn't have an option for "Collects birdhouses in the backyard, all of which are about as tall as the roof".

I'm betting the Purple Martin houses get nailed -- long metal rods, all the way into the ground. Let's just hope they aren't home when it happens. Could be a real mess.

Oh -- I came out "Low".

 

[bphgravity]

The assessment should mirror the result if performed by hand per the NFPA 780. As with any "free" program, especially from a manufacturer with an interest in the result of the program, use it only as a guide or comparison to the actual risk assessment formula.

Like the NEC, the NFPA 780 is rather conservative on particular issues. Risk assessment is one of them, in my opinion.

 

[Fast__Eddie]

I have a few Martin houses in my yard (approx.4 yrs) without lightning strikes... YET.

 

[tallgirl]

I have a few Martin houses in my yard (approx.4 yrs) without lightning strikes... YET.

Mine first has been up for 7 summers without being struck. I suspect I'm fairly safe between the 2 story houses and distribution lines in the 'hood. Which I'm sure would make the Martins happy if they knew they are living in what amounts to a lightning rod ...

 

[don_resqcapt19]

Julie,

I suspect I'm fairly safe between the 2 story houses and distribution lines in the 'hood.

Maybe, maybe not. Lightning goes where it wants to. I worked on lightning damage to a house that was caused when lightning hit the underground phone line in the back yard. The back lot was about 60' deep with the house on one end and overhead utility lines on the other. The burried line was struck about midway between.
Don

 

[tom baker]

The Seattle area is has the lowest amount of thunderstorm days in the US. There are few buildings with LPS, one is a Naval Submarine Base Bangor Stratregic Weapons Facility, with its rumored nuclear missiles, has a LPS.
They are two fences around this building, if you are caught between the fences then its too late.

 

[petersonra]

Excellent link. I ran a test model of my own home and was surprised at the result. It assessed my risk at medium.

Bryan, what is your opinion of the validity of this calculation given that these guys are selling lightning protection equipment.

I think you have to look at what their definition of medium risk is.

It is a lot like what your definition of likely to become energized is.

It said I was a medium risk as well.

 

[tallgirl]

Julie,

Maybe, maybe not. Lightning goes where it wants to. I worked on lightning damage to a house that was caused when lightning hit the underground phone line in the back yard. The back lot was about 60' deep with the house on one end and overhead utility lines on the other. The burried line was struck about midway between.
Don

Most likely that wasn't the direct strike.

If whatever the upward leader is coming from can't handle the strike when the first downward strike occurs, the excess current goes looking for something new to attack. In order for the telephone wire to have been the original target, it would have been able to supply enough current to ionize the pathway from the telephone line to the stepped leader coming from the cloud. That, as they say, ain't very likely.

But, yeah -- doesn't make much difference when ones house is busted up. More likely a pole or tree was hit and the telephone wire happened to be in the path of the current.

 

[don_resqcapt19]

Julie,

If whatever the upward leader is coming from can't handle the strike when the first downward strike occurs, the excess current goes looking for something new to attack. In order for the telephone wire to have been the original target, it would have been able to supply enough current to ionize the pathway from the telephone line to the stepped leader coming from the cloud. That, as they say, ain't very likely.

Direct strikes to the earth are not uncommon. The phone line just happened to be in the ground at that point.
Don

 

[bphgravity]

Any underground cable will be subject to the effects of lightning in a number of ways. Most of the time a direct or near strike will cause localized damaged or signs of high currents or induced currents imposed on the cable itself. When equipment is damaged at a remote structure or building supplied by the cable, this can usually be attributed to frequency coupling (sometimes called "ringing"). Most of the frequencies associated with lightning will have no effect on the cable; however a tuned frequency can impose a transient surge on the cable.

Neither grounding nor bonding will provide any protection against this event. Only properly installed TVSS can be used to as a protective method.