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Author Topic: Chimney mount anemometer mast in lightning prone area. Advice please??  (Read 7450 times)

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Offline w0mbat

  • Posts: 300
  • W Tree, East Gippsland, Victoria, Australia
    • W Tree Weather
I'm most of the way through the process of building a complete 1-wire station to replace my LaCrosse which was destroyed by lightning. The last stage is mounting my new Inspeed Windworks anemometer and windvane kit which has just arrived.
Previously I had my wind gear mounted on a tall mast some distance from the house. But as the windworks gear is separately connected to the weather PC (ie, not through the 1-wire bus) it would be much easier/better if I could mount the wind mast on the chimney of my house.
My house is more or less on the top of a hill and we are in an area prone to thunderstorms. The house is not the highest object on the hill as there are trees within a hundred metres.
My question is is it safe (for the house) to mount a pole on the chimney under the circumstances I have described? The chimney is brick construction and the rest of the house is timber with a metal roof. If I do this should the mast be earthed or not?
I have puzzled over this for a while and would really appreciate the thoughts/experiences of the forum.
Thank you
w0mbat

Offline vk2him

  • Posts: 604
  • Gerringong, NSW, Australia
    • The Shack by the Beach
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #1 on: January 19, 2009, 09:34:28 PM »
G'day,

I'm interested in building a 1-wire system, can you advise if there are any places in Australia selling 1-wire components at reasonable prices?

Cheers

Offline aardvark

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  • Des Moines, Iowa, USA
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Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #2 on: January 19, 2009, 09:37:44 PM »
Ideally  your roof... if it were me I wouldn't use your roof as a mounting area...    I definitely would have it eartherd ( grounded)...
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Offline kray1000

  • Posts: 248
  • Roanoke, VA (USA)
    • Roanoke Valley Weather
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #3 on: January 19, 2009, 11:10:45 PM »
My house is more or less on the top of a hill and we are in an area prone to thunderstorms. The house is not the highest object on the hill as there are trees within a hundred metres.
My question is is it safe (for the house) to mount a pole on the chimney under the circumstances I have described? The chimney is brick construction and the rest of the house is timber with a metal roof. If I do this should the mast be earthed or not?
I have puzzled over this for a while and would really appreciate the thoughts/experiences of the forum.
Thank you
w0mbat

One hundred meters is far enough away from your house that I certainly wouldn't consider those trees to be adequate lightning rods.  Of course, you certainly don't want trees too close to your house either.

The house I grew up in for 13 years was on a similar hill.  We had an underground well about ten feet from a huge tree and even less from a metal clothesline, not far from our house.  The taller tree was never hit, but the well was hit at least twice (one of which I think I witnessed from my school bus about a half mile away).

I agree that brick is not normally a good conductor, but keep in mind that the water that might cover them could be.  And if you have any wires connecting the mast to the house itself (rather than mounting a transmitter to your chimney), I'd be even more concerned.

All that being said, I also believe that grounding may actually increase the chances of being hit, but if it happens, you're MUCH less likely to have a fire as a result.  Proper grounding is a must.

Having any kind of tall object attached to my house would make me nervous.  Others will probably disagree, but if you can find any other location that isn't shielded by your house, I'd strongly consider it.  You're not going to get official-quality measurements at your residence anyway (nobody does if there are trees around).  The fact that you're on a hill already gives you better wind measurements than most. 
« Last Edit: January 19, 2009, 11:20:14 PM by kray1000 »
Kevin Ray

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Offline w0mbat

  • Posts: 300
  • W Tree, East Gippsland, Victoria, Australia
    • W Tree Weather
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #4 on: January 19, 2009, 11:35:08 PM »
Thanks for the answers guys. It looks like my concerns were justified. I'll have to think again.

VK2him..... I have found the USB 1-wire adaptor in Australia for less money (and somewhat quicker) and you can source some individual components(like DS18B20 temp sensors) but assembled instruments generally are not available. I have found that ordering what I need from Hobby Boards in the USA works well. Delivery usually takes about a week.
The mail costs can be steep however.
Regards
w0mbat

Offline vk2him

  • Posts: 604
  • Gerringong, NSW, Australia
    • The Shack by the Beach
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #5 on: January 19, 2009, 11:37:30 PM »
How's this for a close lightning strike .... less than 200m from me ...

Why is everyone so hung up on putting your anemometer on the roof when 99.9% of us also have a TV antenna/ satellite dish  up there???? Wombat, I seems your LaCross was hit by lightning already, is this the first lightning strike you have had in that house? Maybe you were just unlucky as it happens sometimes ..
Cheers

« Last Edit: January 19, 2009, 11:39:08 PM by vk2him »

Offline Jim18655

  • Posts: 11
  • Jonestown, Columbia County, PA
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #6 on: January 19, 2009, 11:42:05 PM »
Check whatever building codes or electrical code that you use in your country or area. I know a lot of people feel it's better not to ground because they feel it attracts lighting but the bottom line is to follow the codes. The last thing you want is a lightning strike and fire and then have your insurance company argue in court that you where negligent with your installation and you were partially responsible for the damages.
They might get out of paying the entire cost of repair.
In the US the National Electrical Code would require grounding a mast if it was for an antenna but I think your mast would have the same attraction to lightning as an antenna. I have my anemometer mounted 10' above the roof on a chimney bracket with a heavy ground wire to a ground rod. The ground should also be connected to any other ground system you have, such as your electric service, unless that isn't permitted in your country.
As far as other things acting as lightning rods and protecting your house, the general rule of thumb I've learned from lightning protection contractors is you're in a zone of protection if you're within an area less than the height of the grounded item you're depending on for protection such as a building that has lighting protection installed on it. I don't think trees would be good enough conductors to count on for protection.

Offline kray1000

  • Posts: 248
  • Roanoke, VA (USA)
    • Roanoke Valley Weather
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #7 on: January 19, 2009, 11:56:02 PM »
Why is everyone so hung up on putting your anemometer on the roof when 99.9% of us also have a TV antenna/ satellite dish  up there????

Because lightning hitting a grounded TV antenna (with lightning being redirected to the ground) is a lot different than lightning running down an anemometer wire to your weather console and computer.
Kevin Ray

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Offline vk2him

  • Posts: 604
  • Gerringong, NSW, Australia
    • The Shack by the Beach
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #8 on: January 20, 2009, 12:08:32 AM »
Because lightning hitting a grounded TV antenna (with lightning being redirected to the ground) is a lot different than lightning running down an anemometer wire to your weather console and computer.

I understand that, however having an anemometer if you already have a TV antenna shouldn't increase your chances of being hit  ... in fact having a grounded TV antenna nearby may save your anemometer from a direct hit ... In Wombats case, as he has a metal roof on his house, he would reduce the likelihood of a direct strike on his antenna or anemometer if he grounded the roof and gutter ...  :)

Offline kray1000

  • Posts: 248
  • Roanoke, VA (USA)
    • Roanoke Valley Weather
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #9 on: January 20, 2009, 12:17:13 AM »
I understand that, however having an anemometer if you already have a TV antenna shouldn't increase your chances of being hit  ... in fact having a grounded TV antenna nearby may save your anemometer from a direct hit ... In Wombats case, as he has a metal roof on his house, he would reduce the likelihood of a direct strike on his antenna or anemometer if he grounded the roof and gutter ...  :)

I wasn't aware that w0mbat already had a mast on his chimney.  Either way, a strike that close to your anemometer would still likely shock your hardware.
Kevin Ray

Wireless VP2, Stardot NetCam, ImageSalsa 2.0.12, MovieSalsa, Nexstorm, WASP2, Skymet, VWS, WD 10.37Nb03

Offline drobbins

  • Posts: 1,699
  • Kentucky, USA
    • Cave Country Weather
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #10 on: January 20, 2009, 01:27:44 AM »
I have been told by a friend who works at the electric co. that the last house on a line is prone to get hit more than other houses. My previous house was one of these lucky houses. We were hit twice in 7 years. I had an antenna that was grounded the first time and the charge went down the ground wire. Unfortunately it jumped through my phone line and killed all the phones also taking out a computer that was connected by modem.

So I took down the antenna figuring that maybe it was drawing the lightening. Then a few year later my Dish got hit and took out a TV.

I built my current house on the lot next door. Last January I put up my weather station. In July it got hit. I thought that because I ran 30' of wire to the hydrosensor and another 50' of wire to the house that the charge would have been dissipated before getting to my computer. Wrong! Lost the weather computer, the weather station, and a LCD monitor.

I have thought about mounting my equipment on the house, but with my luck I won't chance it. If I get hit again, I will buy a good wireless station with more range than the one I have.

I wasn't aware that w0mbat already had a mast on his chimney.  Either way, a strike that close to your anemometer would still likely shock your hardware.
I agree.

Offline w0mbat

  • Posts: 300
  • W Tree, East Gippsland, Victoria, Australia
    • W Tree Weather
Re: Chimney mount anemometer mast in lightning prone area. Advice please??
« Reply #11 on: January 23, 2009, 01:54:51 AM »
Thanks for all the input guys. My internet has been "off" for several days so I have'nt been able to check the forum.
It does puzzle me a little that I can't imagine anyone being bothered by putting up a tv antenna on the chimney.
I think I will go with the mast I already had for my old LaCrosse anemometer. Is about 30 metres from the house. I was trying to both avoid running another underground cable and also minimise the length of cable attached to the Inspeed Windworks box.
Thanks agin for the discussion.
w0mbat

 

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