Author Topic: Mounting poles and NOT attracting lightning.  (Read 1300 times)

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Offline NHWF5510

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Mounting poles and NOT attracting lightning.
« on: November 15, 2017, 03:18:09 PM »
Been searching the internet and having little luck getting a straight answer so i was hoping some members who have a good understanding of lightning can steer me in the right direction. I honestly don't really understand much about it.

I want to install a mounting pole for an anemometer. ideally 20-30' tall. The weather station would likely be mounted on it too.  That being said, i don't want to "attract" lightning. Is a conductive pole a good thing? or a bad thing? Is a tall steel pole set in concrete going to attract lightning more than a steel pole bolted to a 6x6 wood post set in concrete? It's not realistic to go with a wood pole above 10' so that's not an option.

It's bad enough that a lightning strike could damage my weather station, but seeing as all my homes utility wiring is all underground as is my well pump wiring in the general vicinity of where i'm planning to put this pole i don't want to literally set myself up for a disaster.

 We do get a good amount of lightning here and the previous homeowner already replaced a well pump once due to a strike.


Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #1 on: November 15, 2017, 06:16:28 PM »
It's not so much an issue of "attraction", but what's going to happen if lightning hits.

A tall metal pole should be well-grounded.  That way if lightning hits, it will be channeled safely to ground.

If it is not well-grounded (like your steel pole mounted in a wood post example), then the lightning is forced to pass through something of higher resistance (the wood).  The wood will likely explode, if not burst into flame, from the current being forced through it.

Offline chief-david

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Re: Mounting poles and NOT attracting lightning.
« Reply #2 on: November 15, 2017, 07:06:12 PM »
It's not so much an issue of "attraction", but what's going to happen if lightning hits.

A tall metal pole should be well-grounded.  That way if lightning hits, it will be channeled safely to ground.

If it is not well-grounded (like your steel pole mounted in a wood post example), then the lightning is forced to pass through something of higher resistance (the wood).  The wood will likely explode, if not burst into flame, from the current being forced through it.

Yea, but that would be cool.
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Offline NHWF5510

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Re: Mounting poles and NOT attracting lightning.
« Reply #3 on: November 15, 2017, 07:07:57 PM »
Ok, so i'm not making anything "safer" by mounting a steel pole to something wood. Good to know. Ill just set a steel pole in concrete and make sure the bottom is in direct contact with the earth. But my other question still remains,

  Is having a well grounded steel pole on my front lawn going to attract a lightning strike more than say,   the pine trees 50' away that are much taller? i'm just trying to find out if i am increasing the chances of getting a strike by doing this? Or will my giant trees surrounding my property still be more likely to be struck then a steel pole?

 Again, the bottom line is i don't want to open myself up for major damage for the sake of my weather station by doing this the wrong way.

Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #4 on: November 15, 2017, 07:27:35 PM »
Ok, so i'm not making anything "safer" by mounting a steel pole to something wood. Good to know. Ill just set a steel pole in concrete and make sure the bottom is in direct contact with the earth. But my other question still remains,

  Is having a well grounded steel pole on my front lawn going to attract a lightning strike more than say,   the pine trees 50' away that are much taller? i'm just trying to find out if i am increasing the chances of getting a strike by doing this? Or will my giant trees surrounding my property still be more likely to be struck then a steel pole?

 Again, the bottom line is i don't want to open myself up for major damage for the sake of my weather station by doing this the wrong way.

Lightning often hits taller objects first.  It depends on how close they are and how much taller they are.  The further away they are, the less "protection" they provide.

That's not 100% a sure thing, though.  For example, lightning will sometimes strike the side of a tall building or tower instead of the top.

It's just very hard to predict exactly what lightning will do.  That's why it's best to prepare by assuming it WILL eventually hit, and providing it a safe path to ground.

Offline vreihen

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Re: Mounting poles and NOT attracting lightning.
« Reply #5 on: November 15, 2017, 07:53:34 PM »
Ok, so i'm not making anything "safer" by mounting a steel pole to something wood. Good to know. Ill just set a steel pole in concrete and make sure the bottom is in direct contact with the earth.

My $0.02 is to drive a ground stake per NEC recommendations as a minimum.  Personally, I would Google the recommendations for amateur/ham radio operator towers and do that.  Just being in contact with the ground does not guarantee that the sudden discharge will be properly dissipated.

Something to think about.  The lightning bolt jumped a 5-mile-long arc between the ground and cloud.  Why does anyone think that a half inch of rubber or 6-foot wooden fence post is going to stop it?????
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Offline eyecue

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Re: Mounting poles and NOT attracting lightning.
« Reply #6 on: November 19, 2017, 06:15:54 PM »
Lightning always takes the path of least resistance to dissipate its charge.  I  have investigated fires where lightning has done some amazing things. With that being said, a lightning rod or pole grounding is an attempt to divert the strike safely away from what it is mounted on.  Given the power of a lightning bolt though, the lightning rod and associated wires or straps are likely to be reduced to molten material and will be distributed around the area of the strike.  The only thing I have seen survive is a 1200 ft commercial radio tower because it can deal with the current dissipation and had massive distribution points on the base that ran all the way to bedrock.  I would go so far as to say that a lightning rod is a feel good effort. 
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Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #7 on: November 19, 2017, 06:36:52 PM »
Lightning always takes the path of least resistance to dissipate its charge.  I  have investigated fires where lightning has done some amazing things. With that being said, a lightning rod or pole grounding is an attempt to divert the strike safely away from what it is mounted on.  Given the power of a lightning bolt though, the lightning rod and associated wires or straps are likely to be reduced to molten material and will be distributed around the area of the strike.  The only thing I have seen survive is a 1200 ft commercial radio tower because it can deal with the current dissipation and had massive distribution points on the base that ran all the way to bedrock.  I would go so far as to say that a lightning rod is a feel good effort.

I have to strongly disagree.  I've seen the effects of lightning striking my parent's house both with and without lightning protection.  I came face to face with ball lightning inside the house with the unprotected strike.

Lighting rods do their job if properly installed.

Offline eyecue

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Re: Mounting poles and NOT attracting lightning.
« Reply #8 on: November 19, 2017, 06:48:44 PM »
Depends on whether or not it is a feeder branch or direct hit.
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Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #9 on: November 19, 2017, 06:50:21 PM »
Depends on whether or not it is a feeder branch or direct hit.

Duh...  they were direct hits, though.

Saying lightning rods are a "feel good effort" is just insane and irresponsible.

I've seen the results of lightning strikes on all sorts of things as an electrical engineer.  Properly installed, the lightning rods and associated cables don't vaporize.
« Last Edit: November 19, 2017, 06:52:24 PM by nincehelser »

Offline eyecue

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Re: Mounting poles and NOT attracting lightning.
« Reply #10 on: November 19, 2017, 07:05:59 PM »
We will have to agree to disagree!  I had pictures and documentation, you have anecdotes. There is no reason for you to be sarcastic and condescending.
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Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #11 on: November 19, 2017, 07:10:09 PM »
We will have to agree to disagree!  I had pictures and documentation, you have anecdotes. There is no reason for you to be sarcastic and condescending.

I've got way more than anecdotes, bud.  You're the one calling an entire industry "feel good".

Again, lighting protection works.  Otherwise engineers wouldn't be spending all the money protecting structures and equipment.


Offline hankster

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Re: Mounting poles and NOT attracting lightning.
« Reply #12 on: November 19, 2017, 07:13:06 PM »
Maybe the question should be will an individual have the knowledge, take the time and spend to money to properly ground a pole for their weather station?

Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #13 on: November 19, 2017, 07:59:32 PM »
Maybe the question should be will an individual have the knowledge, take the time and spend to money to properly ground a pole for their weather station?

As mentioned before, there are published standards for things such as TV and amateur radio antennas, which have been found to work well.

It's not terribly hard or expensive.  Good sense might be in short supply, though.  The biggest problem I see is that ground rods are often not what they should be.  I've seen some installations where folks have grounded to a water supply pipe outside their house, not realizing the connection to the water main isn't metal (!).  Or they don't sink a copper ground rod deep enough in dry stony soil that isn't terribly terribly conductive.


Offline hankster

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Re: Mounting poles and NOT attracting lightning.
« Reply #14 on: November 19, 2017, 10:29:49 PM »
Straight from the ARRL (National Assoc for Amature Radio) it says http://www.arrl.org/files/file/Technology/tis/info/pdf/0208053.pdf :

The primary purpose of the external ground system is to
disperse as much of the lightning energy as possible into the
earth before it follows the feed line into the radio station. No
matter how hard one tries, some of it will follow the coax,
which is why you created the protection plan for the radio
equipment. The easier you make it for the strike energy to
dissipate in the earth before it gets to the radio station, the
less your equipment protection plan will be stressed.
With great diligence, hard work, no real estate restrictions,
plenty of funds and highly conductive soil, it is possible for up
to 90% of the strike energy to be dissipated in the earth, leaving
just 10% heading for your equipment.

Radials and Ground Rods
Spreading out from the base of the tower is a set of eight
radials. While the number of radials required for a particular
installation will be dependent on the soil conditions in your
location, the system shown here is a reasonable start. Each
radial is a bare copper wire (preferably, strap) buried 6 to 18
inches below grade. The radials should be positioned so that
the energy is dissipated away from the house.
Connected to the radials are ground rods. The ground rods
are spaced approximately twice the length of a ground rod.
For an 8-foot rod, the spacing would be 16 feet.


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Doesn't sound easy or cheap to me :)
« Last Edit: November 19, 2017, 10:33:41 PM by hankster »

Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #15 on: November 19, 2017, 10:37:25 PM »

Doesn't sound easy or cheap to me :)

Not if you're also adding in radials for antenna performance.

He's mixing two different applications.

The NEC codes for grounding antenna masts are nothing like this.
« Last Edit: November 19, 2017, 11:03:29 PM by nincehelser »

Offline hankster

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Re: Mounting poles and NOT attracting lightning.
« Reply #16 on: November 20, 2017, 07:30:23 AM »
Well, you are the one that said look for standards for amateur radio antennas,

Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #17 on: November 20, 2017, 07:54:54 AM »
Well, you are the one that said look for standards for amateur radio antennas,

Yes.  For grounding masts.

And I wasn't the first to bring up the subject. 

Sheesh...





« Last Edit: November 20, 2017, 08:03:58 AM by nincehelser »

Offline DaleReid

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Re: Mounting poles and NOT attracting lightning.
« Reply #18 on: November 20, 2017, 09:07:52 AM »
While a strike can go through a plane, for instance, with minimal or even  no damage, and the space shuttle during launch, and tall buildings and heavily grounded towers may not be hit often, I'm wondering if a very well grounded tower will dissipate the charge building up, and actually thwart a strike from happening?

I've spent many storms watching a 1000' tower here with lightning dancing all around expecting that the easy path to ground through the tower would make it very likely to be hit.  Despite all the watching, never a strike seen, although some of the old old radio guys here in town and the engineers say it does get hit once in awhile.

So a properly grounded tower, big or small, might be draining away the charge and keeping a strike from occurring, or am I wrong on that one?

And I recall some antennas on mobile radios we used to install had a little round BB or bigger sized thing crimped on the end of the wire to cut down on noise, and the explanation was that the round surface dissipated any build up from travel through the air (rubbing cat syndrome, St. Elmo's fire in planes) and that sharp edges like a square cut across the wire makes it more likely to have radio noise. 

Just curious about these two things.
 
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Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #19 on: November 20, 2017, 11:32:43 AM »
While a strike can go through a plane, for instance, with minimal or even  no damage, and the space shuttle during launch, and tall buildings and heavily grounded towers may not be hit often, I'm wondering if a very well grounded tower will dissipate the charge building up, and actually thwart a strike from happening?

I've spent many storms watching a 1000' tower here with lightning dancing all around expecting that the easy path to ground through the tower would make it very likely to be hit.  Despite all the watching, never a strike seen, although some of the old old radio guys here in town and the engineers say it does get hit once in awhile.

So a properly grounded tower, big or small, might be draining away the charge and keeping a strike from occurring, or am I wrong on that one?

And I recall some antennas on mobile radios we used to install had a little round BB or bigger sized thing crimped on the end of the wire to cut down on noise, and the explanation was that the round surface dissipated any build up from travel through the air (rubbing cat syndrome, St. Elmo's fire in planes) and that sharp edges like a square cut across the wire makes it more likely to have radio noise. 

Just curious about these two things.

The first one is an age-old debate.  Stormhighway talks about  it here: http://stormhighway.com/lightning_rods_discharge_thunderstorm_cloud_myth.php

I'm not familiar with the 2nd one.

Offline NHWF5510

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Re: Mounting poles and NOT attracting lightning.
« Reply #20 on: November 21, 2017, 10:05:25 AM »
Thank you all for the information. Some good info being posted here. I still have not really received a clear answer though as to my primary question. Simply put, is adding a properly grounded steel pole going to INCREASE my chances of taking a direct hit even if it's not as tall as adjacent trees? Or will it make no difference at all?

 As for lightning rods, working as both a firefighter and for the railroad i have seen the effects what lightning can do. To say that lightning rods are a "feel good" is completely false. I have been to quite a few house and building fires caused by lightning strikes. I remember a multi family home that took a direct hit to the main sewer vent stack for the house. it melted all the lead joints and set fires in all the walls the pipe passed through. The electric panel was blown completely off the wall and we found pieces of it on the other side of the room. But none were on structures with lightning rod systems.

Lightning has wreaked havoc on the railroad between Boston and NYC where i work. But each time repairs were made and they spent the money for lightning protection the problems never returned. We had one location that used to get hit more than once a year. They finally spent the $$ to properly protect it and it's been fine ever since.

Done right, lightning protection systems are absolutely a worthwhile investment.  Certainly not a guarantee of never having damage, but far better than no system at all.

Offline DoctorKnow

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Re: Mounting poles and NOT attracting lightning.
« Reply #21 on: November 21, 2017, 11:42:58 AM »
The grounding is for "safety", to drain the static buildup into the ground, and should help to not attract lightning as opposed to not grounding a pole and the wind blowing over it and static electrically charging it up. There is never any guarantee that lightning will not hit a pole, but you want to take appropriate measures to be sure that if it does, you take as much of the power of it to the ground outside, and not through your home wiring system to get it into the ground, which is where it is trying to get to in the first place. Lots of damage and fire can occur without a proper ground.

Offline nincehelser

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Re: Mounting poles and NOT attracting lightning.
« Reply #22 on: November 21, 2017, 06:01:23 PM »
Static charge on the mast is irrelevant in this case.

Grounding the mast doesn’t make it any more attractive to lightning.  It would just as likely strike the mast if it were ungrounded.

The difference is the grounded mast would provide a safe path to ground, limiting any damage.  An ungrounded mast, like one separated from ground by wood as you originally suggested, would cause damage as the lightning tries to pass through the wood.

In short, lightning doesn’t “know” how well something is grounded before it hits. 


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Offline NHWF5510

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Re: Mounting poles and NOT attracting lightning.
« Reply #23 on: November 21, 2017, 09:14:47 PM »
Static charge on the mast is irrelevant in this case.

Grounding the mast doesn’t make it any more attractive to lightning.  It would just as likely strike the mast if it were ungrounded.

The difference is the grounded mast would provide a safe path to ground, limiting any damage.  An ungrounded mast, like one separated from ground by wood as you originally suggested, would cause damage as the lightning tries to pass through the wood.

In short, lightning doesn’t “know” how well something is grounded before it hits. 


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  This is interesting. And leads me to another relevant question on the subject of masts and lighting.

 Many people opt to mount their anemometers on the roof. This can be done via a chimney mount, tripod mount or an eave mount. Whatever the mount, these typically support a metal pole and are completely un-grounded. Usually bolted into wood or masonry. But this will almost always mean it's the highest point on the roof as well. Do these become more of a target for lightning? Or are they "invisible" to lightning because they offer no easy path to ground?

Offline wxthomson

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Re: Mounting poles and NOT attracting lightning.
« Reply #24 on: November 22, 2017, 03:08:55 PM »
The grounding is for "safety", to drain the static buildup into the ground, and should help to not attract lightning as opposed to not grounding a pole and the wind blowing over it and static electrically charging it up. There is never any guarantee that lightning will not hit a pole, but you want to take appropriate measures to be sure that if it does, you take as much of the power of it to the ground outside, and not through your home wiring system to get it into the ground, which is where it is trying to get to in the first place. Lots of damage and fire can occur without a proper ground.

I agree
i used to manage data centers and all my buildings had lightning protection systems on the roof.

I have been told several times by the companies that install and maintain these systems that their main purpose is to dissipate the static charge that develops under a large cloud.
thus reducing the potential for a strike.