Old NM cable. To replace or not to replace !

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Davebones

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Friend has a old mobile home built in 1973 he is remodeling .It has 3 conductor copper nm pulled thru-out . It looks good to me as far I can tell but was wondering what some of you contractors that deal with old trailers and remodeling think about replacing it . My background is industrial .Just looking for some opinions about this .
 
I agree with Dennis. '73 romex ain't but hardly broke in by this point.

The only thing that will have degraded the NM (and other wiring methods, for that matter) will be excess heat.

The most likely culprit is the ceiling hugging luminaire that had/has and enclosed incandescant lamp(s). This luminaire traps the lamp heat and the lighting outlet junction box directly above the luminaire achieves temperatures beyond the 60?C rating of the NM plastics for sustained periods of time.

The heat damage will be localized to the lighting outlet, in most cases.
 
Meggar everthing. I assume it's totally exposed. Make them a road map of their circuits.

This protects your statement of it's ok verses the sheet rockers long screws, your map will be priceless.
 
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I'd replace it ,.. here is all you never wanted to know about the life cycle of insulation..
http://www.epa.gov/dfe/pubs/wire-cable/lfs-lca-chap2.pdf

Cables are long-life products; therefore, there is a considerable time lag between when the cables are manufactured and installed and when they reach end-of-life. For example, communications cables have an expected lifetime of 10 to 15 years, due to obsolescence resulting from technological advancements. In addition, low-voltage power cables have a useful life of approximately 25 to 40 years.
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I wouldn't..that information is for LV communications cables, which are a whole different animal, with different insulation materials and more importantly, insulation thickness.

Leave it alone, unless as pointed out there is heat damage from light fixtures.

My apt. is full of 1950's era romex which, other than lacking an ECG, is in perfect condition.
 
no they are talking about both com. and low voltage cables.
Here is another link for chapter one..
http://www.epa.gov/dfe/pubs/wire-cable/lfs-lca-chap1.pdf


The WCP partnership first developed partial life-cycle inventories (cradle-to-gate) of standard
and alternative insulation and jacketing formulations for three selected cable products (Phase I):
1. Category 6, riser-rated communication wire (CMR)
2. Category 6, plenum-rated communication wire (CMP)
3. Non-metallic sheathed low-voltage power cable (NM-B)
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NM-B cables are generally replaced after 25 to 40 years of service, depending on the installation
conditions. During remodeling, NM-B cables are typically replaced only if they are disturbed.
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http://www.doctorfire.com/PVCwiring.pdf
Both UL and IEC assign electrical insulation materials into temperature classes on the basis of 50-
year old research27, and PVC can be rated up to 105?C. But Stricker28 noted that ?although cable
life has not been defined, a life expectancy of 20 to 50 years is reasonable?
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Advice

Advice

Back when I was a teenage lad always under the hood of my car, my dad gave me some useful advice. "Son, if it ain't broke, don't fix it!" :grin:
 
Well this will be the last link I promise...
If he has the dough ,..I'd still change it out...

http://www.kngelectricalservices.com/Aging-Residential-Wiring-Issues.pdf

According to the United States Consumer Product Safety Commission, homes over 40 years of age are the
greater risk, ?but newer ones can have dangers of unacceptable wiring practices and environmental stresses on
their wiring? (CPSC, 2005). Residential wiring systems installed in new or existing houses during the 1960s
and earlier are almost surely at the end of their functional design life.
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So, why wasn't that info included with the wiring? I would never wire a building with wire I 'knew' would have to be replaced during the useful life of the structure.

Okay, let's say I want to build a house to last 100 years. Where am I supposed to find wiring that will continue to function safely over the life span of the house?
 
I didn't read the link but is it possible the reason is the ground on that generation wire is smaller. The OP talks about the 1973 not the sixties. I still see K&T that looks pretty good.
 
100717-1540 EST

In the first report I saw no quantitative data relative to insulation life as a function of anything, temperature, environment, or whatever.

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I would think that if wiring had a finite life span the NEC would address it.


Small wiring [number 14 American Wire Gauge
[FONT=Times New Roman,Times New Roman][FONT=Times New Roman,Times New Roman](AWG)] ... By about 1970, the National Electric Code changed to 12 AWG, thus making the older standard out of date regarding increasing KWH use and peaks. Unless wiring has been upgraded since 1970, then homes are probably wired with small wiring for common branch circuits. [/FONT][/FONT]​

What's this guy talking about? This is what gives homeowner's false information.​

As I see it the problem isn't the wiring itself but improper maintenance of the switches, receptacles and other devices. DIY additions and repairs are also a major problem. We've all worked with wiring from more than 50 years ago that's still in perfect condition. The only exception I found to that is some poorly manufactured AC cable limited to the late 40's with RW insulated conductors where the rubber became brittle throughout the entire cable just due to age.​

An electrical system [FONT=Times New Roman,Times New Roman]doesn't have to meet current standards or code to be safe as long as it meets the code at the time it was installed (with a few exceptions) and is maintained. That's why there is no requirement for upgrading. [/FONT]​

-Hal​
 
1.2 Product Systems
1.2.1 Functional Unit
. . . last sentence . . .
NM-B cables are generally replaced after 25 to 40 years of service, depending on the installation conditions. During remodeling, NM-B cables are typically replaced only if they are disturbed.
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"Replaced". Past tense.

The 1984 NEC introduced the requirement for NM-B (with its 90?C insulated conductors in an 60?C plastic sheath). That's a few months from being 26 years ago.

Has anybody had an up tick of these jobs? Potential clients clamoring?

I've seen absolutely zero activity, ever, for replacing NM-B that has exceeded its "expiration date".

I think this quote is nonsense.

I think that EPA writer, a writer obviously dealing with the boogy man of environmentally hazardous trace compounds, is self aggrandizing.
 
100717-2034 EST

hbiss:

I would suggest that wire insulation has a finite life. Some extremely long, others maybe in the 100 year time frame, and some very short.

The environment and operating conditions have a great effect on this life time.

As an example when I first made use of LVDTs they were only available, off the shelf, with vinyl insulation. I had a number of these at Buick Motor. Within 3 months some of these cables failed. The cause was the hydraulic oil on the machine dripping on the cable leached the plasticizer from the insulation making it rock hard and thus it broke from flexing.

Investigation indicated that Teflon would not have this problem, no plasticizer. Thus, we had to special order LVDTs with Teflon insulation. Problem eliminated.

Before vinyl became available hookup wire used cotton or glass insulation. Rubber was used for test leads and its life was not great. However, I may be able to find some rubber insulated cord, meaning flexible, that is maybe 60 to 70 years old that is still ok.

.

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Davebones said:
Friend has a old mobile home built in 1973 he is remodeling .It has 3 conductor copper nm pulled thru-out . It looks good to me as far I can tell but was wondering what some of you contractors that deal with old trailers and remodeling think about replacing it . My background is industrial .Just looking for some opinions about this .
Click to expand...

Most moblie homes I have seen from that era are in worse shape than the wiring - if the wiring is still original and not modified with the exception of ones wired in aluminum.
 
NM-B cables are generally replaced after 25 to 40 years of service, depending on the installation conditions. During remodeling, NM-B cables are typically replaced only if they are disturbed.
Click to expand...

I would say the first statement NM-B cables are generally replaced after 25 to 40 years of service is an extreme exaggeration, the second statement, depending on the installation conditions. Would be in the cases where heat has affected the outer jacket and insulation.

Now with proper testing and a visual inspection the condition of the insulation can be determined.

This is a government report several things to consider.

Common sense seldom prevails.

These folks have seldom have any real field experience.

Most government agencies have an unwritten goal of expanding their scope and power thereby employing more underlings thus enhancing their position, power, pay and the title on their door. Under Secretary to the Secretary of, Certifying, Inspecting, and Controlling Under Sectaries, that Review NM-B Life Cycles.
 
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