[TowerTalk] THHN wire problem

[Jim Lux]

Hardy Landskov wrote:
> All,
> Thought I would jump in and tell you my tale of woe about using THHN
> insulated wire.
> I bought a 1000 ft roll of  #12 copper from Home Depot to make some 160
> meter radials. After about 2 years, the insulation had turned hard and was
> cracking. When I peeled back some of the insulation from one of the wire
> ends, the wire had a greenish sticky substance all over it. I asked N7IR
> who is fairly knowledgable in chemistry and he said the insulation
> outgasses a substance that attacks the copper. Wish I could remember
> exactly what he said it was.

Probably Chlorine (as in Poly Vinyl Chloride?) which forms a nice green 
Copper Chloride (aka verdigris)

I've only seen it when there was moisture involved (e.g. wire that had 
sat in a flooded conduit AND had cracks in the insulation)

> With that info, I immediately took down all the radials and stripped off
> all the insulation. They were a real mess. The wire cleaned up nicely using
> a soapy type of brillo pad and a garden hose.
> Out here in AZ practically nothing lasts in the heat and ultra violet we
> have. I was happy to catch the problem before it got worse. Of course, YMMV.

I don't know that it would be a significant long term problem. It might 
form the surface layer and then stop.  I don't think it's like rust, 
where it keeps on eating away (after all, there's only a limited amount 
of Chlorine there to do the mischief.. unlike rust, where there's the 
whole atmosphere to provide oxygen in unlimited quantities)

Don't know for sure, though.

Jim