The main reason to cadweld connections is to ensure a good connection over
Yes you can get a very good connection between rod and cable with the brass
clamps and get a much lower resistance connection than the ground rod itself
gives to earth. But the clamp can not be assured of a good connection over
long periods of time compared to a cadweld.
All ground connections should be checked and serviced at regular intervals,
but how many actually do that.
A low resistance connection to a ground rod is not near as important as it
is in other connections of your single point system. There you want a very
low resistance connection in order to maintain low voltage differences
between equipment, supply lines, antenna cables etc.
A few tenths of an ohm can cause a huge voltage difference when thousands of
amps of strike current are passing by.
> -----Original Message-----
> From: TowerTalk [mailto:firstname.lastname@example.org] On Behalf Of
> Jim Lux
> Sent: Saturday, November 17, 2012 10:51 AM
> To: email@example.com
> Subject: Re: [TowerTalk] Grounding
> On 11/17/12 4:40 AM, K1TTT wrote:
> >> Dale - WD4IFR
> >> In any lightning strike, even a 2" solid piece of copper takes on the
> >> characteristics of a light bulb filament.
> > It is simple statements like this that make the rest of what you say
> > questionable. The fact is that MOST lightning strokes hitting even
> > conductors will not significantly heat them. To get any significant
> > in 2" copper is probably even beyond even the largest measured mega
> I agree... take a look at the Preece or Onderdonk equations for fusing
> current. Onderdonk takes into account the pulse length.
> >> BTW -- You do not have to use exothermic welds exclusively for your
> >> ground connections. One of the companies that make crimp on
> >> connectors is "Burndy". These clamps are designed to get away from
> >> Cadwelding but still require the use of a 12 ton crimper to bond the
> > I have never cadwelded a ground connection, most commercial
> electricians I
> > know would probably look at you with complete confusion if you asked
> them to
> > do that. The basic brass clamp sold in every hardware store is what
> > probably 99% of the ground connections in this country are connected
> with is
> > just fine. After all a discharge that has just jumped a mile to the
> > isn't going to be stopped by a few microns of oxide in a connection
> > two conductors. Even lightning rod installers use easily hand crimped
> > splices and connectors.
> the need for exothermic welding or good clamps isn't for lightning. As
> 'TTT says, a few thousandths of an inch gap or oxide isn't going to make
> any difference.
> The good quality bond is for more mundane electrical safety reasons,
> when the 110V wire shorts to the metal case, you want the circuit
> breaker to trip, or, at least, the voltage on the case relative to your
> bare feet to be limited.
> > Oh, one more while I'm at it:
> >> copper braid that are cadwelded (exothermic) to the tower legs. From
> > Braid?? Cadwelded?? I always thought this was a no-no. and who runs
> > for a lightning or safety ground? Don't all codes specify solid
> You can use stranded in larger sizes. There's a lot of 2/0 stranded used
> for this kind of application, for instance. (because handling solid 2/0
> is hard work?)
> I'm too lazy to go get my code book and check, but there IS some
> threshold size for it.
> I wouldn't use welding cable (zillions of tiny strands, so it's real
> flexible). I had bad luck using welding cable for pulsed power
> applications, although I never spent much time figuring out why.
> > I wouldn't trust braid for an outdoor application like that anywhere,
> > maybe you are talking about braid that uses something like 10ga
> AWG 2/0 stranded...19 strands of something like 16.
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