Deterioration of Insulation

Originally Posted By: jtedesco
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It this note still in the code?


I found this in an Article 310 note in the "HI Guide" AKA the 1968 NEC?

Quote:
13. Deterioration of Insulation. It should be noted that even the best grades of rubber insulation will deteriorate in time, so eventually will need to be replaced.


I believe that this information could be used as a good reason to support the concerns expressed over the old knob and tube wiring systems.

Do you agree? ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

Originally Posted By: jpeck
This post was automatically imported from our archived forum.



I did not find it in the current code, but it is definite backup for what I’ve been saying.


Thank you, Kind Sir. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

Maybe I will not be the only voice saying this now. Nah, someone will still say differently.


--
Jerry Peck
South Florida

Originally Posted By: jruddy
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Any indication of how long “eventually” is? Have there been any recent improvements in the insulation that would extend the life?


Originally Posted By: jtedesco
This post was automatically imported from our archived forum.



Hi jruddy:


The word eventually is vague and undefined as it was used, and the text I posted came from th 68 NEC, and it may have been in the earlier editions too.

The life of Type R rubber covered wires that were used in K&T systems, compared to the newer types developed since, have now entered into a second retirement and are usually deteriorated in less than normal conditions.

See 310.10 in the HI Guide AKA the NEC.

Existing electrical systems that were installed as K&T where they are found in walls, or in the attic where we know that the heat is a factor and determinant of operating temperature are almost always as brittle as a pretzel.

Here's a picture of some deteriorated wiring:

![](upload://sCd51Pyi4Ge4mhTKpnoVo12K6M8.jpeg)


--
Joe Tedesco, NEC Consultant

www.nachi.org/tedescobook.htm

Originally Posted By: roconnor
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The design/expected life of a residential building is usually 50 yrs to 75 yrs. I believe HUD uses the 75 yr figure for the entire building before a major rehabilitation or replacement is needed, and I have also heard that 50 yrs is about the maximum for a wiring system (IAEI?).


So IMHO wiring systems older than 1954 would be suspect, and warrant a closer look.

Just my 2-nickels ... ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: jpeck
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FEMA uses a 70 year life expectancy.



Jerry Peck


South Florida

Originally Posted By: roconnor
This post was automatically imported from our archived forum.



Does anyone have a link to what IAEI’s or IEEE’s position is on the design life for wiring systems … I believe it’s considered to be 50 years. Don’t quote me on that until a good reference can be found.



Robert O’Connor, PE


Eagle Engineering ?


Eagle Eye Inspections ?


NACHI Education Committee


I am absolutely amazed sometimes by how much thought goes into doing things wrong