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Brittle THHN insulation on NM-B conductors #185812 03/29/09 04:44 PM
Joined: Nov 2005
Posts: 13
N
newsgraphics Offline OP
Member
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?

2017 / 2014 NEC & Related Books and Study Guides
Re: Brittle THHN insulation on NM-B conductors [Re: newsgraphics] #185813 03/29/09 05:17 PM
Joined: Jul 2004
Posts: 9,571
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gfretwell Offline
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I have seen a lot of the teflon jacket splitting off but the thermoplastic insulation always seems OK.


Greg Fretwell
Re: Brittle THHN insulation on NM-B conductors [Re: gfretwell] #185814 03/29/09 05:19 PM
Joined: Nov 2005
Posts: 13
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newsgraphics Offline OP
Member
Must have been Chinese made wire or something!

Re: Brittle THHN insulation on NM-B conductors [Re: newsgraphics] #185817 03/29/09 09:14 PM
Joined: Nov 2007
Posts: 763
K
KJay Offline
Member
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.

Re: Brittle THHN insulation on NM-B conductors [Re: KJay] #185820 03/30/09 02:15 AM
Joined: Nov 2005
Posts: 13
N
newsgraphics Offline OP
Member
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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