Does wire get a whole lot stiffer with age?

[Milton Shaw]

I recently had a GCFI outlet fail. These were installed about 35 years ago in 4X4 boxes with #12 THHN in conduit. So these were wired as feed through to cover the circuit down stream. That one nearly got to me. The wires were so stiff that I broke the new GCFI trying to get it back in the box. They have 5 # 12's on each one and I could not get them back in the box. I tried rewiring it using WAGO and just stuffing 3 wires with the outlet back in the box. Even that broke one of the WAGO'S. Any body else run into this very stiff wiring. It does not help that there was a 36" loaded grinder work bench in front that I had to lay across or a 12" deep cabinet with the outlet recessed into the back wall. I am now 75 and that may have been a lot of the reason things were so difficult to do. Any body else have similar problems. I had some new #12 Romex and that wire is not nearly as stiff as the 35 year old THHN.

 

[Zeus36]

It's not the wire, it's the insulation.

From the web:

Nylon, the main covering of THHN, is very susceptible to water and moisture, causing additional breakdowns in the wiring under adverse conditions. All of these will cause THHN to wear down and erode, rendering itself useless over the course of several years.

The most direct cause of THHN stranded wire or cable failure is breakdown caused by the degradation of insulation layer.

Due to current overload operation, the thermal effect of the load current through the thhn stranded wire and cable will inevitably cause the conductor to heat up. At the same time, skin effect, eddy current loss of charge and electrical loss of steel armored will also generate extra heat in the thwn wire underground, thus raising the cable temperature, and eventually lead to failure of thhn stranded wire or cable.

 

[sparky 1971]

At 35 years old it's a little before my time but there's a chance it's TW and not THHN. That wire has a big fat insulation and is a little stiffer than the THHN/THWN we use now.

 

[rlitman]

...From the web:

Nylon, the main covering of THHN...

Famous last works. The web is not a trusted source, so please feel free to fact check me, but nylon is NOT the main covering of THHN.

THHN insulation is PVC based, with a very thin clear nylon covering over that designed to protect the PVC from abrasion. TW (the same as the insulation you'd find in old NM before NM-B) had a thicker PVC based insulation that lacked the nylon layer. I wouldn't say the thicker PVC made the older wire all that much stiffer, but I've found it more difficult to pack into tight places.

As for my take on this thread, once I learned to fold my pigtails into a W shaped zig-zag, I've found I can easily accordion that into any box without struggling.

 

[The Cobbler]

Probably , and I'm kind of guessing, the copper gets harder with age

 

[nadogail]

I was told by my new deceased father that Copper “Work Hardens”.

I remember him taking a piece of copper tubing and annealing it by getting it hot and quenching it, just the opposite of steel.

 

[Walkers]

Simply install a much higher amp breaker, short the wires so that they get up to about 800* and they will move much easier after they are annealed.

 

[dogdog]

Copper age hardening but have no idea how op breaks the gfci or wago connections. It’s not like these connections will break because the wire is stiff…..

 

[Zeus36]

Copper will work harden, but will not harden from age or current.

 

[Zeus36]

Famous last works. The web is not a trusted source, so please feel free to fact check me, but nylon is NOT the main covering of THHN.

THHN insulation is PVC based, with a very thin clear nylon covering over that designed to protect the PVC from abrasion. TW (the same as the insulation you'd find in old NM before NM-B) had a thicker PVC based insulation that lacked the nylon layer. I wouldn't say the thicker PVC made the older wire all that much stiffer, but I've found it more difficult to pack into tight places.

As for my take on this thread, once I learned to fold my pigtails into a W shaped zig-zag, I've found I can easily accordion that into any box without struggling.

You are correct: THHN (Thermoplastic High Heat-resistant Nylon-coated) wire is designed with a PVC (polyvinyl chloride) insulated nylon sheath.