Re: [TowerTalk] Power ground

[Tony King - W4ZT <towertalk@w4zt.com>]

I agree with Roger.  Brazed joints in copper are actually called braze 
welding because the heat required to flow the rod (typically a copper zinc 
alloy looking like brass but a different mix with a melting point between 
1630F and 1650F) is near the melting temperature of the copper at 
1981F.  In the welding world, any process done above 800F is either brazing 
or welding but never soldering.  The problems with joints in copper pipe 
systems used for grounding are commonly soldered joints and those are less 
desirable. Exothermic welds create the same kind of joint as you would 
create while brazing though in a quicker simpler form.  Though some of us 
are equipped to braze and weld, many folks aren't. The exothermic welding 
devices (by any name) are much easier to keep and use and the resulting 
connection will always "LOOK" better because of the mold but electrically 
they can be identical to brazing.

From my post here on 10/21/2003:
"If you look at MIL-HDBK-419A, Grounding, Bonding, and Shielding for 
Electronic Equipments and Facilities, (available as the complete 2 volume 
set at http://www.tscm.com/MIL-HDBK-419A.PDF but a large file around 9.7 
mb) you'll find that brazing and exothermic bonding are the two recommended 
methods (by the military) for joining components in a grounding 
system.  Brazing requires higher temperatures than soldering so you would 
use oxy-acetylene or mapp gas, brazing flux, filler rod (brass, brass alloy 
or silver alloy are common) and technique but it is far superior to solder 
in both strength and conductivity when used in similar materials 
(copper/bronze/brass etc). Brazing can be done easily with a little 
practice but care must be taken that the filler material flows into the 
joint, not just lays on top of it."

73,
Tony W4ZT



At 01:57 PM 5/26/2004, you wrote:
> I've been following this for a while and keep seeing reference to "brazed"
> water pipes.
> I've never seen a brazed joint in water pipes. Soldered, but never brazed.
>
> The temperature for brazing is much higher than soldering and would be
> enough to show some serious oxidation on the copper.  Brazing would require
> the copper to be at a "cherry red" heat to get the stuff to melt.  In most
> homes the amount of heat required would cause charring on any wood near the
> joint.
>
> It may not be permitted, but I'd trust a good brazed joint any day over a
> compression fitting that can corrode.  I've had compression fittings
> completely lose contact with ground rods.
>
>
> Roger Halstead (K8RI, EN73 & ARRL Life Member)
> N833R, World's Oldest Debonair (S# CD-2)
> www.rogerhalstead.com
>
>
> > In a message dated 5/26/04 10:17:54 AM Pacific Daylight Time,
> > wilsonlui@atitec.com writes:
> >
> > > However using
> > >  brazed water pipes is not recommended. The brazed connections represent
> a
> > >  seriously weak electrical joint and may fail prematurely under thermal
> > >  stress of high currents.
> >
> >     Yessireebob. The only NEC ground connections allowed are compression
> and
> > exothermic (i.e. Cadweld).
> >
> > Cheers,
> > Steve     K7LXC
> > TOWER TECH -
> > Professional tower services for commercial and amateur
> > 888-833-3104

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