Wiring exposed to sewer gas

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  #1  
Old 01-22-07, 06:04 AM
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Wiring exposed to sewer gas

This past weekend I discovered a disconnected plumbing vent pipe in my finished basement. Besides the obvious sewer gas issues all the NM cable in the immediate vicinity of the "leak" has severly discolored. This exposure has existed for about 2-1/2 years since the house was built. It was hidden by fiberglass insulation between the floor joists of the 1st floor.

This is within 5-6 feet of the main panel where various circuits converge and run to the panel. The sheathing seems intact but has turned a coco brown color. It is darkest close to the leak fadng back to the original white or yellow of the original wire 4-5 feet from the leak. The discoloration does not wipe or rub off, it appears to be a color change in the plastic.

Has anyone had this experience or know of any longterm problems of the wire being exposed to sewer gas? Any suggestions of who to contact or where to look for this information?

Your help greatly appreciated.
 
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  #2  
Old 01-22-07, 08:04 AM
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Location: Milwaukee WI
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From
http://www.southwire.com/processGetArticle.do?commonId=b06660f3b370ff00VgnVCM1000002702a8c0____

NM-B:
Nonmetallic-Sheathed Cable. The "B" denotes that individual conductor insulation is rated 90C; however, ampacity is limited to that for a 60C conductor (see NEC Section 336-26, 1999 edition). Thermoplastic (PVC) conductor insulation-nylon jacketed, with overall PVC cable jacket.

PVC is the same stuff used for some sewer pipes, but I am not a chemical or plastics engineer.

You might want to inquire with the wire manufacturer, whose name should be on the cable somewhere, about the NM-B jacket's susceptibility to damage from exposure to sewer gas, which I think is mostly methane and hydrogen sulfide.

FYI I've got grey electrical PVC that looks "sunburned" to a brownish tint. I probably overheated a spot a little when I was bending it. Are you sure you're not seeing heat damage from nearby pipe soldering?
 
  #3  
Old 01-23-07, 08:33 AM
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Wire not overheated

Originally Posted by ArgMeMatey View Post
From
http://www.southwire.com/processGetArticle.do?commonId=b06660f3b370ff00VgnVCM1000002702a8c0____

NM-B:
Nonmetallic-Sheathed Cable. The "B" denotes that individual conductor insulation is rated 90C; however, ampacity is limited to that for a 60C conductor (see NEC Section 336-26, 1999 edition). Thermoplastic (PVC) conductor insulation-nylon jacketed, with overall PVC cable jacket.

PVC is the same stuff used for some sewer pipes, but I am not a chemical or plastics engineer.

You might want to inquire with the wire manufacturer, whose name should be on the cable somewhere, about the NM-B jacket's susceptibility to damage from exposure to sewer gas, which I think is mostly methane and hydrogen sulfide.

FYI I've got grey electrical PVC that looks "sunburned" to a brownish tint. I probably overheated a spot a little when I was bending it. Are you sure you're not seeing heat damage from nearby pipe soldering?
Thanks for the information from the Southwire website.

The wires in questions are definately not discolored due to heat as there are no soldered pipes in the basement. All the supply piping is CPVC and the discoloration is not an isolated spot, its on multiple wires over a three plus foot length in multiple floor joist bays.

I did contact the manufacturer. Spoke to the product engeneer who didn't feel there was any damage to the sheathing just a discoloration of the plastic. He did refer my question to there plastics engineer but I haven't heard anything back.

Thanks Again.
 
  #4  
Old 01-23-07, 05:26 PM
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Alot of worry for nothing. You should see where some of this stuff is.
 
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