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#185812 - 03/29/09 02:44 PM Brittle THHN insulation on NM-B conductors
newsgraphics Offline
Member
Registered: 11/05/05
Posts: 11
Loc: California
Last night I was installing a ceiling fan in our relatively new house (built in 2005). It was pre-wired for ceiling fans, so this should have been an easy installation. However, after twisting the wire nut onto two of the conductors, I noticed that the insulation on the THHN jacket had literally split and exposed the bare copper wire!

Admittedly, I did crank those wire nuts on tightly, but I have never had a problem with insulation splitting like this before. I ended up having to cut it back about two inches. Has anyone else had this occur before?
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#185813 - 03/29/09 03:17 PM Re: Brittle THHN insulation on NM-B conductors [Re: newsgraphics]
gfretwell Offline


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Registered: 07/20/04
Posts: 9039
Loc: Estero,Fl,usa
I have seen a lot of the teflon jacket splitting off but the thermoplastic insulation always seems OK.
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Greg Fretwell
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#185814 - 03/29/09 03:19 PM Re: Brittle THHN insulation on NM-B conductors [Re: gfretwell]
newsgraphics Offline
Member
Registered: 11/05/05
Posts: 11
Loc: California
Must have been Chinese made wire or something!
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#185817 - 03/29/09 07:14 PM Re: Brittle THHN insulation on NM-B conductors [Re: newsgraphics]
KJay Offline
Member
Registered: 11/27/07
Posts: 763
Loc: MA, USA
Just wondering, did you remove the NM outer jacket with a utility razor knife or maybe use those Klein NM cable stripping pliers?
I've often seen the type of problem you described when these tools are used.
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#185820 - 03/30/09 12:15 AM Re: Brittle THHN insulation on NM-B conductors [Re: KJay]
newsgraphics Offline
Member
Registered: 11/05/05
Posts: 11
Loc: California
Hard to say what kind of tool was used by the original installers, this is a tract home, but your suspicions sound quite plausible.
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