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Joined: Oct 2000
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so is there a defined life span of wiring methods?

where would one reference this?

~S~

Joined: Jun 2006
Posts: 613
M
Member
Sparky

There is always a design limit but it is not necessarily defined. It is the point where all the materials science runs out of data. For example a spec for sunlight resistance might require some type of insulation to withstand exposure to sunlight for 20 years. Well they don't stick the wire outside and wait 20 years. They stick the wire in a box and shine artificial light on the insulation for a period of time and at an intensity high enough to simulate 20 years of exposure. In the real world some will be installed in Arizona and some in Alaska. The UV protection is the same but the wire in Arizona is more likely to fail sooner than the wire in Alaska. The wire was engineered to last a period of time and any day after that is bonus.

So how long is a lifetime? I have heard that electrical equipment is engineered for something like 40 years. So we don't replace it at 41 years but the design was for 40 years and every day beyond is bonus. Our older houses were designed to accommodate a light bulb and a plug in every room. Most outlets beyond those installed for appliances were also expected to accommodate a plug in light since not that many other household appliances existed. We overloaded these circuits and overheated the wires. The insulation degrades and gets brittle from heat. Eventually the wire will lose it's protection and become a hazard.
There has also been the handyman adding and modifying the circuit as well as new hotter fixtures being connected.
The wiring system is on borrowed time. Even the newest K & T is at least 50 to 60 years old. It is all borrowed time. Sure there are houses where the old wiring is in pristine condition and serving the same function but there is no data to indicate the date of ultimate failure. Maybe it is 500 years or 200 but we all see that these old systems are on average, past the expiry date. Old wiring might last a very long time and well past the original design but like everything, it all eventually fails.
If only a product could predict its last day of operation and account for all the variables of use and abuse. We would wake up one morning and the circuit for the counter would just dissolve or stop working without all the safety hazards. The house computer could have called the electrician and arranged replacement dates and scheduled a work plan. It could predict what parts of the system are soon to fail and we would always have an up to date and failsafe system.

Joined: Oct 2000
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Originally Posted by mikesh
Sparky

There is always a design limit but it is not necessarily defined. It is the point where all the materials science runs out of data. For example a spec for sunlight resistance might require some type of insulation to withstand exposure to sunlight for 20 years. Well they don't stick the wire outside and wait 20 years. They stick the wire in a box and shine artificial light on the insulation for a period of time and at an intensity high enough to simulate 20 years of exposure. In the real world some will be installed in Arizona and some in Alaska. The UV protection is the same but the wire in Arizona is more likely to fail sooner than the wire in Alaska. The wire was engineered to last a period of time and any day after that is bonus.


interesting, i read something similar in one of the trade mags about how they tested circuit breakers, solo, by itself. My first thought was all the 'real world' applications, like being sanwhiched bettween other breakers (amibent heat)

Quote
So how long is a lifetime? I have heard that electrical equipment is engineered for something like 40 years. So we don't replace it at 41 years but the design was for 40 years and every day beyond is bonus. Our older houses were designed to accommodate a light bulb and a plug in every room. Most outlets beyond those installed for appliances were also expected to accommodate a plug in light since not that many other household appliances existed. We overloaded these circuits and overheated the wires. The insulation degrades and gets brittle from heat. Eventually the wire will lose it's protection and become a hazard.


No argument here, i've filled more dumpsters with K&T and/or BX than i care to recall, many many 'brittle' terminations, etc....


Quote
There has also been the handyman adding and modifying the circuit as well as new hotter fixtures being connected.


the bane of our profession....

Quote
The wiring system is on borrowed time. Even the newest K & T is at least 50 to 60 years old. It is all borrowed time. Sure there are houses where the old wiring is in pristine condition and serving the same function but there is no data to indicate the date of ultimate failure. Maybe it is 500 years or 200 but we all see that these old systems are on average, past the expiry date. Old wiring might last a very long time and well past the original design but like everything, it all eventually fails.


The problem is two fold then, we are not talking milk here, there's no expiration date , and in truth the manufacturers aren't about to make anything that is 'large print'.

Who can blame them really?

next is the 'if it ain't broke, don't fix it' contingent, and i'm sure nobody here needs a lecture on those sorts....

Quote
If only a product could predict its last day of operation and account for all the variables of use and abuse. We would wake up one morning and the circuit for the counter would just dissolve or stop working without all the safety hazards. The house computer could have called the electrician and arranged replacement dates and scheduled a work plan. It could predict what parts of the system are soon to fail and we would always have an up to date and failsafe system.


true that we could have some better , or maybe more inclusive assessment system , weather it be outside intervention (annual inspections like fire alarms?) , or internal assessors (like enhanced software)

this , however, is where credit might (just might) be given to where it's due.

Because now we have the mighty afci, which i'm to understand mitigates both series as well as parralel faults. So it would seem reasonable to consider them, given series being the major brittle factor fault in K&T

This , of course, would be in lieu of a rewire job, but if we are going to buy time until then, i would , and have , suggested it a viable 'bandiad'

In fact, i've garnered one insurance company that's signed onto this idea, and kept a K&T infested coffee shop in town under their coverage for the time being

Further still, one could , at the panel, place a gfci after the afci, couldn't they? The next step is chasing down the brittlisms that cause it all to trip.

Yes , i know, 'bandaids' stick around long enough to be voting age, a problem in of itself. But faced with say, a 10K rewire , as well as the cost of imported french wallpaper being replaced, why can't this be a consideration?

~S~


Joined: Dec 2009
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jimbob Offline OP
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i agree but some people are not willing to rip up floors and ceilings.i thought if it was still flexable without breaking the insulation it was still good.not the best by any means. thanks for all the insight.

Joined: Jun 2006
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I can appreciate that selling a rewire in an old house has its challenges. I'd caution That assuming the wire is in good shape because it is flexible where you can get to it and thinking it is in the same shape where it is concealed is a dangerous assumption.
It is just impossible to predict an ultimate failure date as there are just too many variables. Sure the copper should last thousands of years but the insulation has no millenia of data to show its mean failure.

Sparky from your post I am assuming that you don't know that arc fault breakers have ground fault protection built in. It is not GFCI protection and trips around 30 milliamps instead of the 6 MA for GFCI protection.


Joined: Dec 2007
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JUST MY 2 CENTS. BUT TELL THE CUSTOMER IT NEEDS A TOTAL REWIRE. IF THEY DON'T WANT TO PAY, WALK AWAY. I'VE WORKED FOR MICKEY MOUSE CONTRACTOR'S WHO ARE WILLING TO PUT IN OLD USED BULLDOG BREAKERS IN A RELIC PANEL AS AN EXAMPLE. I USED TO SAY, TELL THE CUSTOMER THEY DON'T EXIST. I WOULD'NT EVEN KEEP THAT OLD GARBAGE AROUND MY SHOP IF I HAD ONE, NOT WORTH THE HEADACHES.

Joined: Aug 2007
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I SEE K&T that has been in use for 80+ years in better shape than NM in use for 20 yrs.

Most damage is at the devices. Where exposed to all that deadly O2.
(That Mr. Gore wants to out law) (OOPS)
However,I do recommend it to be -Upgraded- Not changed- Unless serious issues are found.

Most issues 'Needs' can be addressed with a service upgrade or new ckts to an already upgraded service.

Most N&T I see,is in better shape than the added stuff.

Last edited by leland; 01/06/10 02:37 AM. Reason: Surprise
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Quote
Sparky from your post I am assuming that you don't know that arc fault breakers have ground fault protection built in. It is not GFCI protection and trips around 30 milliamps instead of the 6 MA for GFCI protection.


well i believe that would make it a GFPE here MikeS, and no, nobody really knows all the parameters of the AFCI.

but that's really inconsequential , given the situation i have repeatedly stepped into around my turf , the insurance companies are dictating what is, and what is not 'safe' wiring, at least in that limbo term 'existing' is applicable

i've approached some, or suggested my customers approach them, with the idea of installing afci's

explaining that it stands for 'Arc Fault' and that one can contact the manufacturer for details

The onus of credibility is then, shifted bettween these entities , they decide, not me.

and why shouldn't it? any AHJ can ask me here to produce manufactuer's information on any electrical item i install, i've just kicked it all upstairs to where the real movers and shakers are

I've explained this to the local AHJ too. He's conceeded to my methods as the bandaid that it is. About ten years ago i also wrote UL asking the same Q, but they did not forward a detailed reply.

In an economy where few have the $$$ for a complete rewire, and a biz can get shut down , or a homeower rejected by the insurance cabal , any sanctioned avenue is going to be investigated

my methods from this point are typical, usually done in stages. 1)split up the older larger circuits into a number of derated ones, 2) investigate & reterminate with plastic enclosures (not metal) 3)provide new dedicated circuitry where applicable 4)GFCI at point of use where required.

so they eventually get a rewire anyways....

~S~




Joined: Jun 2006
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Sparky
I like that "Insurance Cabal". The are selling insurance but it is poor business to sell only to the high risk guys. Actuarial data indicates that most house fire are in houses older than 40 years. I can't comment on what data they use to determine risk but if it motivates people to at least visit the current state of their electrical systems, then I am on their side. It also makes for more work for us, also good. My experience indicates that it is actually removing a lot of the abused wiring around town. Sure there are a few Little old ladies that have never blown a fuse and are living in the same house for 60 years. Never a home handyman or contractor has ever altered or damaged the wiring. I still have a couple of 120 volt 30 amp services here just waiting for a change of ownership to get an insurance upgrade. Nothing lasts forever and with only a hundred years of electricity in houses there are still a lot of risks that have not been measured yet. Code books don't make rules for upgrade except for a couple of rules in section 2 that speak to maintenance.

Last edited by mikesh; 01/06/10 02:48 PM.
Joined: Oct 2000
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Actually i'm probably being too hard on the insurance industry Mikes, hard not to being a contractor.

In this case, you've a point in that they really are the only game in town pointing out what is obvious to us in our trade, yet oblivious to much of the general public....

Especially in those catch 22 'existing' situations, which i tend to stumble into more than i really care to

~S~

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