Liquid Tape: An acceptable repair for damaged 480V wire?

[Jon456]

IMO, this is not the right test method for this conduit run. You should find an application that is an industry standard.

If there's an established industry standard for testing damaged conductors in dry conduit, we would LOVE to see it! This contractor throws out BS excuses and roadblocks at every opportunity to try to avoid being responsible for his work. He initially rejected ANY megger tests, claiming it could damage the wires. If we insist upon a Hi-Pot test without solid and incontrovertible documentation to support our position, he will claim that the damage was caused by our test and not by his shoddy workmanship. I know that the insulation will withstand the Hi-Pot test if it's undamaged. I also know that if the Hi-Pot test were to damage the insulation, it wouldn't look anything like the damage caused by dragging the wire over the metal edge of the LB. But this contractor, despite having a degree in EE, is not the brightest bulb in the box.

Just to give you an idea of his mentality, his propensity to blame anyone but himself, and his lack of critical thinking, let me give this little example...

One of the conductors to our inverter #2 was damaged; this was in buried PVC conduit. We agreed to allow him to intercept the run midway by cutting in a new pull box. The location of this new pull box was selected to be adjacent to an existing pull box for inverter #3. He hired a day laborer to help him dig the hole for the new box, and they piled the dirt and sand on the ground nearby. The conduit was cut, the damaged wire replaced, the conductors were tested, and then the new Christy box was installed. But what happened to the extra sand that was excavated from the conduit trench? It could have been simply spread out on the ground (bare dirt between two buildings), but it wasn't. I discovered that someone opened the pull box for inverter #3 and shoved all the sand in there, filling it above the openings of the conduit with sand spilling down into the conduits. I didn't witness the final installation of the new Christy box, so I don't know who actually did this. I suspect it was some laborer he hired to finish installing the box. When we notified the contractor and told him he needed to clean out the extra sand, he didn't say, "I'm sorry, the guy I hired must have done that. I'll take care of it." Instead, he tried to blame it on me. This is what he wrote to our manager (in two separate emails):

"Lastly, the before photo (marked invert #2) and after photo (re-marked invert #3) that you attached, are of the pull box for inverter #3. [Contractor's company] has not conducted any work in this box other than re-labeling the pipe prior to your flooding of the conduits. However, the after photo clearly indicates that flooding of the conduits or water intrusion has washed sand or dirt into the pull box and perhaps into the conduits."

"Your claim that we put dirt in inverter #3 pull box is simply untrue. As previously stated, we have not conducted work on inverter #3 electrical lines nor work in the pull box. However, we note that you had been working with Power One on inverter #3 ongoing issues. We warned you about the potential damage to equipment while flooding conduits and observed [Jon456] flooding of the pull box. As part of your system maintenance, we recommend that you remove the dirt from the pull box and vacuum out the sand in the conduit to keep the area clean."​

So here are the before & after photos taken of the pull box for inverter #3 (note that the contractor had labelled the conduit incorrectly as "Inverter #2" during the original installation; he remarked it recently):

Firstly, we had flooded the #3 inverter conduit for testing during the first round of testing and all the wire within passed. We did not re-test these #3 inverter wires during the second round of testing after the other damaged wires were replaced. So this conduit never got flooded at the time when the sand appeared.

Secondly, does that look like sand that has been washed in by water? Perhaps this contractor never played in a sand box or at the beach, but water flowing slowly out of the conduits wouldn't deposit sand in loose, crumbly piles above the level of the conduit openings.

Thirdly, if he's claiming that all that sand was washed out of the conduit that he installed, then I would have to question the quality of his conduit installation!

This is a trivial problem; I could easily send one of my workers to clean out that box. But this illustrates the level at which the contractor will stoop to avoid taking responsibility for his work.

 

[zbang]

This is a trivial problem; I could easily send one of my workers to clean out that box. But this illustrates the level at which the contractor will stoop to avoid taking responsibility for his work.

It's amazing when people spend more time coming up with new excuses than just fixing the problem would take.

 

[Jon456]

May get even more difficult to fill if set screw fittings were used

All compression fittings on the EMT.

I usually have no problem with getting underground raceways full, they seem to get that way on their own. One instance I specifically recall - I buried PVC conduit on a Friday, came back next Monday to pull conductors. It was hot and humid - but of course the underground portion was cool and it condensed in there. No rain over the weekend either. Was not full but just over the weekend was enough condensation in there that my pull rope came out damp.

At our property, the ground water table is very high. In the winter, all the in-ground boxes will flood because the water cannot drain into the earth. One of the buried 4" PVC conduits was still completely flooded with water when I opened the Christy box in latge March. (That's how I discovered that this conduit contained yet another damaged 480VAC 500MCM wire to one of our inverters: as I was inspecting some wires in that box, I stupidly touched the water in that conduit and got shocked.) So it's patently absurd for the contractor to have claimed -- and continues to claim -- that flooding the conduits can damage the wires. I even confirmed with the wire manufacturer that they test their wires immersed in water.

In any case, the problem arises when one end of the buried conduit is at a lower elevation than the other. Even packing the low end opening with duct seal (around and between, for example, six 350 MCM wires) cannot adequately contain the water enough to completely flood the conduit. The other problem can be "hills" in the buried conduit run than can create air-locked pockets.

The XHHW insulation is excellent at shedding water and there is no nylon jacket that can trap water at the site of any insulation damage. So unless the area where the insulation damage can be fully wetted and kept wet, it is difficult to get a meaningful megger test.

 

[kwired]

Underground location is a wet location - whether intentionally flooded or not - then if you have high water table - it may be flooded year round if you are having a wet year.

This guy needs to be slapped with a wet fish.

 

[FionaZuppa]

I didn't witness the final installation of the new Christy box

mistake #1. if you didnt, who on your side did? the ongoing issues means you need to hover like fly on shiat, etc.

in last few posts.......... why "fill & test", why not "pump & test" ??

 

[Jon456]

mistake #1. if you didnt, who on your side did? the ongoing issues means you need to hover like fly on shiat, etc.

I agree with you about needing to watch him like a hawk. The problem is this contractor is unethical: he knows that I observe and document everything, and I'm not afraid to call him out and stop him when I see him doing something wrong. His solution is to be dishonest and deceptive in order to do his work without our knowledge or presence.

We tell him to give us advance written statements of his methods & materials, and he fails to do so (or gives us some meaningless BS statement without actually telling us anything). We tell him to give us his schedule for when the work is to be done, and he lies (e.g., tells us on Wednesday that he's going to do work on Friday; but then does it Thursday instead.) We tell him to notify us when he's going to make a repair so we can witness the work, and instead he "sneaks" onto our property and doesn't notify us until afterwards.

As for the installation of that Christy box, he did that surreptitiously on the day that his sub-contractor was replacing all of our damaged main feeders and some of the damaged PV feeders. I was busy observing the feeder pulls and working with the independent testing company that was megger testing the newly replaced wires. So I didn't have time to shadow the contractor all day to see what he was up to.

We really didn't expect there to be an issue with setting the top ring and backfilling the box (the lower extension ring was already in place over the conduit). Besides, who could have imagined that he'd open a closed pull-box that's perfectly fine and dump the excess excavated sand into it, when the sand could have simply been spread out on the bare dirt surrounding these two boxes? His modus operandi is to spend the least amount of time and do the minimum amount of work to complete the job.

in last few posts.......... why "fill & test", why not "pump & test" ??

Pump & test? Would you please elaborate?

 

[Jacob S]

All compression fittings on the EMT.


At our property, the ground water table is very high. In the winter, all the in-ground boxes will flood because the water cannot drain into the earth.

In any case, the problem arises when one end of the buried conduit is at a lower elevation than the other. Even packing the low end opening with duct seal (around and between, for example, six 350 MCM wires) cannot adequately contain the water enough to completely flood the conduit. The other problem can be "hills" in the buried conduit run than can create air-locked pockets.

This is a long shot, but is it possible that the water could be freezing in the conduit, in the winter time, damaging the insulation?

 

[FionaZuppa]

Pump & test? Would you please elaborate?

if you cant hold a fill in the pipes for whatever reason, then pump water continuously while doing the test, etc.

 

[Jon456]

This is a long shot, but is it possible that the water could be freezing in the conduit, in the winter time, damaging the insulation?

No, not at all. We're in a very temperate climate zone: never too hot or too cold. During the winter months we may get a little surface frost, but it never gets cold enough to freeze anything below ground. Additionally, we've seen the damage on a number of conductors that have already been pulled and replaced. It's clearly due to improper installation.

 

[Jon456]

if you cant hold a fill in the pipes for whatever reason, then pump water continuously while doing the test, etc.

I understand. The problem would be the same because we'd still not be able to achieve a water-tight seal at the low-end of the conduit, so the water would still be flowing out past the wire bundle as we're pumping it in. Unless we could pump in a volume exceeding the rate at which the water is escaping. But if we were to increase the rate-of-flow too high, it would just blow out the duct seal due to back-pressure.

The other concern is that the low-end of the conduit is typically at an in-ground pull box, while the high-end is typically in a panel. Flowing water into the conduit from a hose at the high-end poses little risk of damage to the electrical equipment because it's being gravity fed, not forced into the conduit at high-pressure. Plus I can stop the flow in an instant when the water backs up to the top of the conduit. If I'm pumping water in from the low-end, I risk a geyser at the conduit high-end inside our electrical panels.

The only real solution that I can see is to use an expanding closed-cell foam (like Polywater's product) to seal the low-end opening. But that would make it difficult to R&R any wires that test bad.

 

[zbang]

As an aside- if he's coming on property when you don't expect it and he doesn't have blanket permission to be there, that might be considered trespassing.

 

[kwired]

Sounds like it may cost more to fight with this guy then to just dismiss him and be done with him. Then find someone else to fix any issues still remaining. May need to eat some cost but down time from failures could cost more depending on the application.

Do you still owe this guy any money? I wouldn't pay him anything still owed. Maybe even consult some legal counsel before doing anything for or against this guy.

 

[pjholguin]

I concur, @Jon456 consult an attorney and see where you can cut this guy loose...to see what you can recover. How is he getting on the property? Does your company have a security force?

Sounds like it may cost more to fight with this guy then to just dismiss him and be done with him. Then find someone else to fix any issues still remaining. May need to eat some cost but down time from failures could cost more depending on the application.

Do you still owe this guy any money? I wouldn't pay him anything still owed. Maybe even consult some legal counsel before doing anything for or against this guy.

 

[PetrosA]

...
The only real solution that I can see is to use an expanding closed-cell foam (like Polywater's product) to seal the low-end opening. But that would make it difficult to R&R any wires that test bad.

I recently sealed some conduits with the Polywater product and it's actually pretty easy to chip out. It gets brittle once it hardens so if you were to put a thinner barrier in than they recommend, it would probably be removable without too much trouble. For a hundred bucks you could order a tube and do a few mockups to experiment. I"m thinking maybe a 1-2 inch barrier versus the five inch they recommend for water sealing...

 

[FionaZuppa]

I understand. The problem would be the same because we'd still not be able to achieve a water-tight seal at the low-end of the conduit, so the water would still be flowing out past the wire bundle as we're pumping it in. Unless we could pump in a volume exceeding the rate at which the water is escaping. But if we were to increase the rate-of-flow too high, it would just blow out the duct seal due to back-pressure.

The other concern is that the low-end of the conduit is typically at an in-ground pull box, while the high-end is typically in a panel. Flowing water into the conduit from a hose at the high-end poses little risk of damage to the electrical equipment because it's being gravity fed, not forced into the conduit at high-pressure. Plus I can stop the flow in an instant when the water backs up to the top of the conduit. If I'm pumping water in from the low-end, I risk a geyser at the conduit high-end inside our electrical panels.

The only real solution that I can see is to use an expanding closed-cell foam (like Polywater's product) to seal the low-end opening. But that would make it difficult to R&R any wires that test bad.

you cant pump in faster than its leaving, water is not a compressible fluid (and it wont leave faster than input unless gravity is pulling hard enough to create cavitation).

a slow input rate from high side should suffice, the goal is to force out all the air and not allow air in while pumping the water. this might indeed be tough with wires coming out of the end, etc.

 

[Barbqranch]

Personally, I don't see any reason why all the air should have to be forced out. Really all you need is a conduction path between any insulation breaks and the conduit. Even areas out of the water stream will get a lot of humidity which will most likely create a conduction path.

ps. a minor comment on something that is a personal nit pick of mine, water is compressible, as is everything else. Only it is not very compressible. If it didn't compress, then sound waves would travel in water at (or above) the speed of light. This is just my physics teacher reminding me of odd facts.

 

[FionaZuppa]

ps. a minor comment on something that is a personal nit pick of mine, water is compressible, as is everything else. Only it is not very compressible. If it didn't compress, then sound waves would travel in water at (or above) the speed of light. This is just my physics teacher reminding me of odd facts.

yikes, too technical for here. for water, 0.0046 % @1atm, 0.004% @250atm. its not a significant factor until you get into critical processes like nuclear fission, etc.

 

[K8MHZ]

Personally, I don't see any reason why all the air should have to be forced out. Really all you need is a conduction path between any insulation breaks and the conduit. Even areas out of the water stream will get a lot of humidity which will most likely create a conduction path.

ps. a minor comment on something that is a personal nit pick of mine, water is compressible, as is everything else. Only it is not very compressible. If it didn't compress, then sound waves would travel in water at (or above) the speed of light. This is just my physics teacher reminding me of odd facts.

Another scientific issue is the fact that water does not conduct electricity and the ability to conduct fault current would depend on other things dissolved in the water.

Maybe add a little salt???

:?

 

[FionaZuppa]

Another scientific issue is the fact that water does not conduct electricity and the ability to conduct fault current would depend on other things dissolved in the water.

Maybe add a little salt???

:?

unless you have some fairly expensive gear, you dont have access to pure water.

do not add salt, it will be corrosive. even high mineral content water might be too corrosive to use in this method.

if water is used, after tests are done i might consider blowing the pipe out with air for a period of time, and then introduce some rubbing alcohol to disperse any remaining water, and then air again to evap the alcohol. this is likely all not feasible.

 

[Jon456]

you cant pump in faster than its leaving, water is not a compressible fluid (and it wont leave faster than input unless gravity is pulling hard enough to create cavitation).

a slow input rate from high side should suffice, the goal is to force out all the air and not allow air in while pumping the water. this might indeed be tough with wires coming out of the end, etc.

I know that water is -- for all practical purposes -- incompressible. My point was that if I tried to pump water into the low-end of the 4" conduit at a rate greater than what could flow past the bundle of six 350 MCM wires, then the resulting pressure would simply blow out whatever seal I have at the low-end.

As far as filling from the high-end, the gravity flow into the conduit is restricted by the wire bundle. As the conduit fills, it develops enough head pressure such that the rate-of-flow past the duct seal at the low end is equal to the rate-of-flow into the conduit past the internal restrictions. So it reaches an equilibrium point where the conduit is partially filled, but cannot be completely filled.