Thread: wire life span

I've searched through the archive and my NEC book and haven't found anything so far.
Does anyone have a reference guide or life span tables for electrical wire and equipment?
Any resource would be greatly appreciated.
Thanks, Markus

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Originally Posted by Markus Keller

I've searched through the archive and my NEC book and haven't found anything so far.
Does anyone have a reference guide or life span tables for electrical wire and equipment?
Any resource would be greatly appreciated.
Thanks, Markus

With the insurance industry they use 30-40 years. With my litigation support work this has been the number of years that we have used in a few cases that involved electrical systems. Pretty much any electrical system that is pre 1960 is outdated and special attention needs to be given to it.

I don't think you will find a published source. My information came from underwriters and insurance cost replacement guides. Codes do not address the age or life of a system.


Nothing last forever.

Someplace I read 40 years, but ...

Was that for:

- the original varnished insulated wiring

- rubber insulated wiring

- knob and tube of either above or any type

- thermal plastic insulation (modern day wiring, dating from the 1950s, give or take)

- in conduit (same problems with the wiring, it just contains the fire)

- you see where this is going ... Based on what wiring type?

How long will modern day NM cables with thermoplastic insulation last? A long time. How long? Don't know.

Other than modern day wiring with modern day thermoplastic insulation, the wiring probably needs to be replaced.

Some of that original TW is getting a bit stiff too.

Thanks for the ins info Scott.
Jerry is way too knowledgeable, his last line 'TW'.
The issue at hand is a recent insp in a studio condo
Older highrise condo insp; Bldg. was built in the mid 60's +/-
The 6 fuse main panel 6" from the kitchen sink has to go (only 4 sockets work). No GFI's of course anywhere; most receps either have paint or are brittle. Those are all pretty simple matters.
The point of contention is the wiring throughout. Appears to be original TW wire, the Columbia or Paranite/Parasyn manufacturer most likely. Those were the common ones around here. Came in flat cardboard boxes, I remember them from way back. (Odd the things we remember and forget)
On the one hand if the wire is original that makes it +/- 40 years
On the other hand, from my recollection and talking with my Dad (retired GC), the TW usage around here stopped sometime in the mid late 70's, which would put the wire at +30 years.
I'm recommending replacement based on either age. Seller won't be happy. I checked the wires at various locations. Some really stiff, brittle; some really soft rubbery (heat build-up/high draw?). I just don't see the wiring lasting safely.
Any suggestions for backup?
Thanks, Markus

I would also add that many of the insurance providers will no longer cover or if they do cover the home it will be at a higher rate for homes with fuse panels.

Scott, I forget to add in the ins info. Luckily I saw your post before I emailed the report out and added it. Thanks for the reminder.
Markus

Originally Posted by Markus Keller

I checked the wires at various locations. Some really stiff, brittle;

Deteriorating due to age.

some really soft rubbery (heat build-up/high draw?).

Heat (high current draw creating heat) would tend to make it harder and brittle. 'Cooks' the insulation, if you will.

Being as TW was never "soft and rubbery", that would indicate a failure due to contamination, such as some type of solvent had gotten on the insulation and has damaged it.

Rubber insulation was "soft and rubbery", but after 40 years it would be "hard and brittle". Besides, I doubt anyone still used rubber insulated wires in the 1960s. Not even sure it was available then, thermoplastic had replaced it starting in the late 1940s to early 1950s, surely by the 1960s rubber insulation had gone the way of the dinosaur.

Typically most wire useally last 20~40 years.

It all depending on the useage and location it runs.

Yeah.,, I know some do last longer but again all upon useage.

Basically in the NEC it say nothing about how long you have to replace the wires or cables.

It more fall on common senses when the time to replace it.

Merci,Marc

See NEC 310.10 FPN in part for some ideas too:

"The principal determinants of operating temperature are as follows:

(1) Ambient temperature — ambient temperature may vary along the conductor length as well as from time to time.

(2) Heat generated internally in the conductor as the result of load current flow, including fundamental and harmonic currents.

(3) The rate at which generated heat dissipates into the ambient medium. Thermal insulation that covers or surrounds conductors affects the rate of heat dissipation.

(4) Adjacent load-carrying conductors — adjacent conductors have the dual effect of raising the ambient temperature and impeding heat dissipation."

Mr. Peck added some good comments about the old R Type insulation, and in addition we should also be reminded that TW insulation was one of the reasons for the changes back in 1984 when they started the NM-B rules for Romex calling for double HH.

Look in an earlier code for the Note in 310 concerning deterioration.

Thanks, for the responses guys, very helpful.
Markus

Joe,

Good to see you here again.

Question, what would you guess would be the life of wiring today (manufactured within the last decade)?

Have them made enough improvements in the technology to have that wiring last 50-60 years (when used properly, not overheated, etc.).

The real life of rubber insulation was probably only 20 years or so. Thermoplastic TW was a big jump. Newer insulation (THHN, etc.) another big jump. Then add in for better engineering, technology, and quality control over materials ... ?

Originally Posted by Jerry Peck

Joe,

Good to see you here again.

Question, what would you guess would be the life of wiring today (manufactured within the last decade)?

Have them made enough improvements in the technology to have that wiring last 50-60 years (when used properly, not overheated, etc.).

The real life of rubber insulation was probably only 20 years or so. Thermoplastic TW was a big jump. Newer insulation (THHN, etc.) another big jump. Then add in for better engineering, technology, and quality control over materials ... ?

Jerry:

I agree with your spread of 50-60 years, why in my own condo unit here in the North End of Boston, MA that was wired in 1981, the 4-wire feeder SER and all of the circuit conductors in my panelboard show no signs of deterioration, or where they are getting old!

I expect to live for another 33 years, that will make me 100 years old, so I can keep watch, unless I die before then!

Are you in this picture? Who are these people?

DSC02221.jpg - Image - Photobucket - Video and Image Hosting

Originally Posted by Joe Tedesco

Are you in this picture?

No.

Who are these people?

DSC02221.jpg - Image - Photobucket - Video and Image Hosting

My guess is (based on the fact that 2-3 of them look like people I worked with on Mike Holt's 2005 Changes to the NEC video): that is the panel for Mike Holt's 2008 Changes to the NEC video. I don't remember their names.

Reading through my new IAEI magazine I just got last Friday and there is an article on the life expectancy of ground rods.

Their research testing and results (see 4.).

The main conclusions that can be drawn from our study are as follows:

- 1. Galvanized ground rods will corrode at a significantly faster rate than their copper-bonded counterparts.

- 2. The zinc coating on galvanized rods corrodes at about 3 times the rate of the copper coating on the copper-bonded rods.

- 3. A grounding system based on typical galvanized rods will have a lifetime of about one-third that of a system based on typical copper-bonded rods. (Jerry's note: Bold was their in the article.)

- 4. Our results are in excellent agreement with a 50-year-old National Bureau of Standards field study, which showed that galvanized and copper-bonded rods have a service life of 10-15 and 30-40 years respectively. (Jerry's note: Bold and underlining are my highlighting, not in the article.)

- 5. Within the uncertainties and statistical variation of the experiment, the results showed that typical installation damage such as scratches and dents on the coating of the ground rods does not affect the corrosion performance of the rods.