Conductor life expectancy

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nizak

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A customer recently questioned me about the life expectancy of two different installations.

- Type xhhw aluminum conductors in PVC conduit vs direct burial copper conductors in earth.

Soil appears to be just black dirt with a bit of sandy mix.

Any ideas on which install would last longer?

Thanks.
 
nizak said:
A customer recently questioned me about the life expectancy of two different installations.

- Type xhhw aluminum conductors in PVC conduit vs direct burial copper conductors in earth.

Soil appears to be just black dirt with a bit of sandy mix.

Any ideas on which install would last longer?

Thanks.
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Where I often work, you must factor rodent activity in that equation, they don't seem to care if it is copper or aluminum, you need raceway for both.

That and excavating equipment is also hard on underground wiring.

Telephone company plowed right through power line I installed that was only there for a couple weeks. The guy knew it was there, planned to raise the plow when crossing it, but forgot all about it when he got there:blink:
 
kwired said:
Where I often work, you must factor rodent activity in that equation, they don't seem to care if it is copper or aluminum, you need raceway for both.

That and excavating equipment is also hard on underground wiring.

Telephone company plowed right through power line I installed that was only there for a couple weeks. The guy knew it was there, planned to raise the plow when crossing it, but forgot all about it when he got there:blink:
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I just have to ask.
What does durability/longevity have to do with wires being plowed or dug to destruction?
 
nizak said:
A customer recently questioned me about the life expectancy of two different installations.

- Type xhhw aluminum conductors in PVC conduit vs direct burial copper conductors in earth.

Soil appears to be just black dirt with a bit of sandy mix.

Any ideas on which install would last longer?

Thanks.
Click to expand...

XHHW in conduit is almost unbeatable from a reliability standpoint.
 
myspark said:
I just have to ask.
What does durability/longevity have to do with wires being plowed or dug to destruction?
Click to expand...



ALL and ANY factors that lead to 'no power' are part of durability/longevity. Just like the rodent comment.

Reminds me of the Honolulu airport 40 years ago. A mainland contractor used aluminum conduit in the soil, very reactive volcanic soil. Some conduits failed within 3 years.

Termites so ferocious that direct burial lead sheathed telephone wires in the 30s and 40 which used paper insulation had termites literally eat thru the lead to get to the paper.


ALL factors part of longevity! Reliability numbers for satellite wiring even take into account remote chance of meteor strike, in addition to common degradation mechanisms like radiation, temperature and electron deposition which are barely factors in buried terrestrial cables.
 
myspark said:
I just have to ask.
What does durability/longevity have to do with wires being plowed or dug to destruction?
Click to expand...
I'll admit being plowed isn't exactly a condition you prepare for. If it were, I should have run RMC instead of PVC, maybe even encased it in concrete.
 
nizak said:
A customer recently questioned me about the life expectancy of two different installations.

- Type xhhw aluminum conductors in PVC conduit vs direct burial copper conductors in earth.

Soil appears to be just black dirt with a bit of sandy mix.

Any ideas on which install would last longer?

Thanks.
Click to expand...

Both will probably outlast him short of some physical damage. And PVC conduit is not of as much help in that regard as you might think.

Having said that, a guy from ComEd told me they are mostly not installing DB cable anymore by itself. They are running single conductor DB cable in PVC conduit in most cases, except where it is a repair situation. He told me this is for a lot of reasons, mostly earth shifting can grab the conductors and damage them, whereas inside the PVC they can move around even if the PVC conduit itself is broken. Who knows what the real reason is, or whether what he told me is even true. It seems plausible though from the few installations I have seen of late.

ETA: Supposedly this is also easier to repair for some reason.
 
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Nicked insulation on conductors during install that later fail - you just pull them out and pull new ones in if you have raceway.

Something damages the raceway and/or the conductor - you will likely be excavating anyhow.
 
Around here frost goes down 5 feet and brings rocks up into wires.
 
kwired said:
I'll admit being plowed isn't exactly a condition you prepare for. If it were, I should have run RMC instead of PVC, maybe even encased it in concrete.
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I'm still unclear on how a plow hit your pipe, and how lifting the plow would somehow save it as the truck runs it over. I'm sure there's a logical explanation, but those are my first thoughts.
 
jaylectricity said:
I'm still unclear on how a plow hit your pipe, and how lifting the plow would somehow save it as the truck runs it over. I'm sure there's a logical explanation, but those are my first thoughts.
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The "plow" in question is a wire plow that spreads a narrow slot, lays the cable in at the bottom, and lets the slit close behind it. Used a lot for phone and cable installations.
The weight of the machine is almost certainly too low to damage properly covered pipe.
Lifting the plow just lays that portion of the cable at a shallower depth where it passes over existing infrastructure.

Sent from my XT1585 using Tapatalk
 
GoldDigger said:
The "plow" in question is a wire plow that spreads a narrow slot, lays the cable in at the bottom, and lets the slit close behind it. Used a lot for phone and cable installations.
The weight of the machine is almost certainly too low to damage properly covered pipe.
Lifting the plow just lays that portion of the cable at a shallower depth where it passes over existing infrastructure.

Sent from my XT1585 using Tapatalk
Click to expand...
Exactly what happened. I installed electric line in PVC to a garage and to the house (both were moved to a new site) maybe two - three weeks earlier both were buried approximately 30" deep. Telephone company comes with something similar to this


to install telephone line to the house. I was there the day they did that, told him what I ran and what else was existing in the vicinity (was on a farm place with other existing buildings that also had feeds in the vicinity. He decided since it was still fairly obvious where these new lines were at and we knew approximate depth of them he would just go over them with the plow raised , as his normal depth was pretty close to what I had buried my lines at. He was too busy with concerns of how they were going to tie into main lines and rework some of what was on that end, that he completely forgot about these lines when he got to them.
 
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