I would beware of any kind of connection that depends on mechanical pressure
for contact, especially if the bus ring is buried in the ground. If
soldered, you must use brazing material like silver alloy. I once used
plain old lead/tin solder, and had to go out and resolder all the radials
every 2-3 weeks. The chemicals in the soil decomposed the solder and it
turned to a white powder, and the radials just fell off the ring.
My present setup used silver alloy brazing rods, installed about 25 years
ago. I just dug down to the bus ring a couple of weeks ago to inspect. The
brazed connections are all still intact.
I purchased my brazing rods from a plumbing supplier. It has long been a
violation of code to use lead/tin solder for copper pipes because the lead
in the solder may leach into drinking water, and lead solder deteriorates
just like it did with my radial system, and the pipes eventually leak. The
codes require a special silver solder sold for the purpose. The rods come
in about 18" lengths, flat stock, about 1/8" wide. It takes a hot torch to
reach the melting point of the solder. Ordinary propane won't do it, but a
Mapp Gas torch works very well. The copper must be heated to a dull red.
No flux is needed, and the copper need only be cleaned well enough to get
rid of any scaling oxide on the surface. Once the alloy melts, copper soaks
it up like a sponge soaks up water. The rods aren't cheap, but not
outrageously expensive either.
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