[Gone Coastal]

I'm in the unfortunate role of being on an HOA board tasked with overseeing the lights in our neighborhood. The board this year decided the 20+ year old lights along the streets of the neighborhood need replacing. One of the members tossed out the idea that maybe we should consider replacing the buried wire while we are doing the project, claiming that it's been 20-25 years since it was installed so it must be needing replaced sometime soon. I don't have any reference for how long buried wired should last. I could fathom if it was done properly then much longer than 25 years should be achievable.

If this wire did need replacing and it was buried in conduit, any idea on what kind of cost we'd be looking at for new wire runs? It would be about 4000ft.

 

[gregzoll]

Only as long as no one nicks the wires, and that the connection points at the lights in the base were properly done, when they were put in. Only reasoning that I can think of that one person wanting to replace the 20 year old lights, is to go with LED, and that they are really starting to get beat up, since they do save money in the long term, along with maintenance costs of having to replace bulbs every 3-5 years. You still have the maintenance on the Photo cell though.

Costs is one thing that cannot be discussed, due to it varies area from area, and no telling what all is involved in the work.

 

[k_buz]

I don't know how large the neighborhood is, or how many lights you are talking about, but replacing the wire would be a very large additional (possibly) unneeded expense. Replace or repair the underground as needed.

 

[AllanJ]

If the old lights are working almost normally except for being dirty, the wires can be left as-is when you upgrade to new lights.

It is possible to test the wires, one conductor in one portion of run, between two light fixtures, at a time. Create a circuit using one length of underground wire unwirenutted from the system at both ends, about 200 watts worth of incandescent lamps in parallel, and enough additional 12 or 14 gauge wire needed to get from a power source.

Measure the voltage across the lamp terminals. Change the wiring around so just the lights and not the test section of underground wire is in the circuit but do not omit any of the loose additional wire from the circuit. Measure the voltage across the lamp terminals again. A significant difference in voltage means the underground length of wire is defective.

Repeat for other portions of the run.

 

[gregzoll]

Actually AllanJ, the company that would be doing the work, would hook up a Megger to test the wiring, to decide if it is worth keeping or tossing. Also as I stated before, depends if there was ever any damage done to the wire, or what the soil is like, would also determine what the next step they would take.

Our Fairgrounds here in Springfield, IL, just had the whole wire distribution system updated around three years ago, due to the wiring was in some areas over 50 years old and starting to cause phase shorts, etc, due to the loads placed on the lines over the years did its wear and tear on it.

The only system they never touched was the street lighting system, which I doubt the state will ever do anything with that, until the insulation on it wears so bad, that it starts shorting out and causing system failure. That system is going on over 60 years out there.

I know of parts of our city, that there are underground lines in some unincorporated areas that Ameren-IL/Cilco maintains, that is well over 70 years old and showing its age.

 

[deverson]

I'm not sure if I would trust the company to meg the wires and give you an honest answer. Kind of like leaving the fox in charge of the henhouse!

 

[gregzoll]

I'm not sure if I would trust the company to meg the wires and give you an honest answer. Kind of like leaving the fox in charge of the henhouse!

Any company that does that type of work, would not be a run of the mill electrical company. We had to do it all of the time on the Ship to Shore cables, especially when we got to the Philly yards, due to you never knew how bad they were, until you got to the port.

I cannot count how many times we had phase to phase shorts, that would sit there and overheat, then give you a nice fire to roast hot dogs by, and never would they trip the breakers, which usually were 400 amp per phase.

 

[Gone Coastal]

Measure the voltage across the lamp terminals. Change the wiring around so just the lights and not the test section of underground wire is in the circuit but do not omit any of the loose additional wire from the circuit. Measure the voltage across the lamp terminals again. A significant difference in voltage means the underground length of wire is defective.

I c, so basically comparing the underground versus the known good test wire to see how much the drop is down the underground length? Is that just showing degradation in the copper making it have higher resistance?

the company that would be doing the work, would hook up a Megger to test the wiring, to decide if it is worth keeping or tossing

Aren't meggers just testing the insulation? Or, is the test Alan describes also going to reveal problems with the insulation as well?

 

[gregzoll]

Yes, it reveals problems with the insulation to make sure that it is not breaking down, to allow shorts, or degrading of the Copper wiring from the soil reacting with it.

 

[al_smelter]

Do you know what type of system and voltage you have? Our plant has around 4000 ft of street lighting as well. We use a constant current transformer and high voltage cable. It is a series circuit, which requires two cables. You can send power a very long distance with a constant current system. Our wire size is #6 with 5kV insulation.

Just curious as to what your neighborhood has.