Re: [TowerTalk] There's 'ground', and then there's 'ground'

["Alan NV8A (ex. AB2OS)" <nv8a@att.net>]

But note that special fittings are required for connecting aluminum 
conductors to copper ones to avoid corrosion resulting from electrolytic 
action.

Alan NV8A


On 01/16/05 01:04 pm Jim Lux tossed the following ingredients into the 
ever-growing pot of cybersoup:

> > When I went looking for home lightning rod suppliers on the Internet, it
> > appeared that all vendors for this kind of service are still selling this
> > braided aluminum stuff, and only this.
> >
> > I guess I'm perplexed -- if it doesn't conduct lightning well, how can
> > these people continue to sell it and stay in business?  I'd think their
> > liability headaches would be phenomenal> >
>
> I'll speculate..
>
> Aluminum is a fine conductor, and cheaper (for a given current carrying
> capacity) than copper.  The notorious problems with aluminum wiring in
> houses are more to do with installation practices and terminations, not the
> wire itself.  Virtually all power transmission lines use aluminum as the
> conductor (over a steel core), including the lightning protection wire above
> them all.  So, aluminum, if properly installed, isn't inherently a problem.
>
> As for the braiding, while it's not ideal, perhaps it's "good enough" to
> keep the building from burning down (which is the goal of most lightning
> protection) as opposed to preventing your equipment from being damaged by
> transients.
>
> And, don't forget the economic dimension... in theory, you don't want to
> spend more on the system (and installation labor) than the statistical
> expected return.  For example, if the probability of lighnting hitting your
> house is, say, 1:10,000 in any given year, and if no protection were done,
> the damage would be $100K, then the economic value of the protection is only
> $10/yr....     Here in Southern California, nobody has lightning rods on
> their houses.  Lightning is just too rare to justify the expense.
>
> I grant that you (and many others, including myself) will gladly pay much
> more than that to transform an unlikely huge loss into a regular loss of a
> small amount (this is what homeowner's insurance is all about, after all).
>
> The other thing is that relatively few houses have 100 foot metal things
> sticking up into the air next to them.

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