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kebwi 07-14-2012 11:34 PM

Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
I'm trying to learn how lightening grounding usually works. It seems like a conventional approach is to use a nearly 4' solid copper rod driven all the way into the ground...that's expensive.

Any ideas? Is copper necessary? Is 4' necessary?

Laku 07-15-2012 12:54 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
It's about conductivity conductivity of metals. You could substitute copper with silver, but some how I don't think you'd like that any better. ;)

Thick 1 cm (2/5") bare copper wire will also do the grounding trick if it's long enough. It's dug at least 0,5 meters (2 feet) to the ground (usually in a circle around the protected building).

Something like this
http://www.tukes.fi/Tiedostot/sahko_...ukkoskuva1.gif

kebwi 07-15-2012 08:17 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
I realize copper is more conductive than other typical materials. What I don't understand is why it makes any difference in a lightning rod. The current is going to follow the available path of least resistance and just about any metal would make a good path for electricity to follow...so wouldn't a steel spike direct lightening into the ground just as easily?

By the same logic, if only copper will do, so how does attaching a cable to the foot of my aluminum pole work at all? Don't I need to lead a copper cable up to the top of the pole (and a second cable up to the top of the stove-pipe)? Neither of those is made of copper. One is stainless steel and the other is aluminum. What do those not have to be copper by the spike in the ground does? I'm sorry, I just don't understand that.

Laku 07-15-2012 08:41 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
Other metals do conduct better than most of other stuff, but the more conductive it is the more sure the lightning will travel along that path and not jump/fork to something you don't want it to. Then there's also corrosion to consider. Also the less conductive then more resistive the material is and that will cause it to heat more when passing current trough --> additional fire hazard.

That's how I've understood it, just a layman's opinion though so keep that in mind.

kebwi 07-15-2012 08:49 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
Right, but is the implication that I should not only use a copper spike in the ground, but also that I should run heavy gauge copper cable up to the top of my support pole and also to the top of the stove-pipe?

That seems absurd, but it's one or the other. I mean, I don't see much purpose in using copper at and below ground level to ground a tall metal structure which isn't copper. Am I wrong? Is it perfectly sensible to use a copper spike to ground an aluminum pole and a steel stove-pipe?...or should I just go ahead and just steel (the more conductive of the two metals involved in this discussion).

Laku 07-15-2012 09:03 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
I think it is, considering the huge amount of current lightning will produce.

I think they only connect the corners on metal roofs to grounding, so don't know about having to run the wire all they way top. Then again the amount of metal in a roof will ensure that the resistance isn't going to get high enough to set anything in fire.. I think

Way I see it the copper is best suited material to transfer enough current and still be discreet as possible. Other metals would need to be thicker to pass through the same amount of current without heating too much.

here's something on the subject I found with quick search

Gulf 07-15-2012 09:56 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
On the electrical poles down here they have the copper attached to the full length of the pole. The wire is twisted into a coil and attached underneath the base of the pole. When the pole is set, the weight of the pole is setting on the coil of copper. I think the coil of wire must give it more area of contact with the earth. Of course they do require grounding rods at the service entrance of the home, though. The reason copper is requred for earth contact is that steel will eventually turn into a ball of rust and probably would be less of a ground at that point. I think that your aluminum pole would have enough mass to be a good conductor. I would just run a copper ground from the top of the chimney to the pole. Then I would secure another length of copper wire to the base of the aluminum pole and then to a copper ground rod.

kebwi 07-15-2012 10:25 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
Thanks Gulf. Sounds expensive. I actually suspect the 4" to 3-1/2" aluminum support pole doesn't provide more metal for electricity to flow through than the 7" double-walled steel pipe, despite the pole's 1/8" thickness (since the stove pipe is two concentric walls of significantly greater circumference than the pole, and I believe steel is more conductive than aluminum, so for a given thickness it generates less resistance...I think).

Of course, there's the question of whether the support arm between the two structures is solid enough to transmit lightening from one to the other such that I need only ground one of the two structures (ostensibly the pole). I have been considering using copper pipe as the support arms between the pole and the stove pipe, just for aesthetic reasons. Perhaps this is another good reason for that approach. :-)

I'll see what copper cable costs, I don't want to spend as much on a lightening system as the rest of the system put together. Good grief.

Thanks.

kebwi 07-15-2012 10:29 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
I seriously doubt that this thing will ever take a strike. There are several 80-footish trees in the immediate viscinity (within thirty-forty feet of the oven) and a church steeple just two lots away (to say nothing of my own house's roof, which will be of comparable height and only thirty-forty feet away).

Part of the reason for this super long stove pipe is that the oven is on really low ground. In the end, after I build this thing, the top of the stove-pipe will still be lower than that of many other roof-stove-pipes in the area. The only thing that makes it look so electrical is that it will be one rather long pipe instead of a short pipe one top of a roof (and the 14' support pole next to it).

Cheers!

Laku 07-15-2012 11:28 AM

Re: Any thoughts on electrically ground a tall stove-pipe (and support pole)?
 
There's a formula of a sort to that kind of protection

http://www.tukes.fi/Tiedostot/sahko_...ukkoskuva2.gif

How trees (and tall buildings/structures if conductive enough) affect protection angle

Trees all around the building alpha= 60
Trees on two opposite sides of the house alpha = 50
Trees on one side of the house alpha = 30
Solitary tree alpha = 25

Everything that is inside of that is almost perfectly protected.


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