Any Ideas?

Status
Not open for further replies.
PVC conduit installed underground seems like it always gets moisture inside. We always plug the ends of our conduits but there is still water in the pipe when we pull, we always swab the conduit before pulling.

The underground wire you installed is probably rated for water such as XHHW or the such. Maybe it would have been better to just direct bury it. That way the water could not just absorb into the wire.

If the wire was installed with just a simple nick in the insulation, it usually causes the wire to corrode. They always told me the electricity somehow traveled on the outside of the wire, and if you nicked a half mark in the insulation, you cut the voltage rating in half.

I have located and repaired a ton in aluminum undergrounds with the Progrssive fault finder. It would literally find the fault within an inch. Everytime we found a fault, there had to be some type in imperfection or nick in the wire, unless a gopher chewed into it. Seems like wire just really does not go bad in a short amount of time for no reason, unless you have some weird deal like lightning or a wild surge to exceed the voltage rating of the jacket.

I don't know about thawing the wire, seems like if you dump hot water into it, it will only make more ice after it freezes. Seems like maybe the best option would be to lay a temp service, in conduit on the ground until you can get the wire out. Keep us posted on what comes about.
 
This situation brings up two issues for me.

The first is why pull direct burial cable in PVC?

The second is the reason I don't use aluminum. I hate it. I have seen the power co. installed a service lateral and in 2 weeks it has gone bad. I totally agree with the previous post that aluminum with a knick in the insulation is a unwanted destiny. It will go bad and fast.

Copper in conduit cost more but I sleep better at night.

Also many reasons why PVC gets water in it is because most contractors don't prime the joints, as the plummers always do. I do realize condensation also plays a roll.
 
Dennis Alwon said:
This situation brings up two issues for me.

The first is why pull direct burial cable in PVC?

The second is the reason I don't use aluminum. I hate it. I have seen the power co. installed a service lateral and in 2 weeks it has gone bad. I totally agree with the previous post that aluminum with a knick in the insulation is a unwanted destiny. It will go bad and fast.

Copper in conduit cost more but I sleep better at night.

Also many reasons why PVC gets water in it is because most contractors don't prime the joints, as the plumbers always do. I do realize condensation also plays a roll.
Click to expand...

This installation is no different than what the local POCO would have done. You use conduit incase of a problem down the road, (upgrade, whatever) this situation is rare, and we wont know the true problem until more investigation occurs, my thoughts are that the pipe is broken and the neutral along with it... but we will have to wait and see...
 
Dennis Alwon said:
This situation brings up two issues for me.

The first is why pull direct burial cable in PVC?

The second is the reason I don't use aluminum. I hate it. I have seen the power co. installed a service lateral and in 2 weeks it has gone bad. I totally agree with the previous post that aluminum with a knick in the insulation is a unwanted destiny. It will go bad and fast.

Copper in conduit cost more but I sleep better at night.

Also many reasons why PVC gets water in it is because most contractors don't prime the joints, as the plummers always do. I do realize condensation also plays a roll.
Click to expand...

Why not use the direct burial? It is about the same cost as xhhw and everyone stocks it. Around here nearly everyone does their underground services using the direct bury use triplex in pvc.

And I can't argue that copper is better.

I do clean all my pvc joints.

And I've also seen a small nick lead to failure of a conductor. I'm as sure as I can be that there wasn't a nick in this. I pulled it myself by hand through a much larger pipe than was needed.

I'll post what happened when I figure it out.
 
I too have seen AL turn to toothpaste many times. Sometimes you can't even see the initial damage to the jacket but it bent like a garden hose. Open it up and...yuck. We sleeve all our underground when it passes under a walkway or driveway as the frostline will be dramatically deeper there. I'd hesitate dumping anything down that pipe at all. Besides, if you are "positive" no damage was done to the jacket (what about defect?), then the pipe must have damaged it therefor rendering the pipe useless. We have temped in 80 on the ground or done a temp overhead in these situations til we could dig it up. Recently we started using 2" flexible carflex as well which seems a better fit for our frost conditions in MN. Frozen 80 will snap like a twig with enough heave pressure.
Good Luck
 
Here's what happened: http://picasaweb.google.com/quinellakid/PowerProblem?authkey=_trFqm9ZjA8

Some of the pic's didn't come out so great, but you can get the idea. I'll try to get some better ones tomorrow.

We sent a snake down each end. Obstruction was right above steel 90 at pole. Dug out and exposed 90 and a bit of the pvc. (To be clear, it is pvc the whole way, except changes over to RMC 90 with steel riser at pole. Per poco requirements)

Fortunately this winter had been so warm around here until recently that there was no frost. Just the grass was froxen a bit. And fortunately the backfill was pure sand all the way.

We started to cut through the pvc with the intent to cut right through conductors as well. As soon as we cut through the pvc, water came shooting out as if under pressure. BTW, the 90 is the lowest point of this entire run, so I guess technically the water was under pressure. We kept cutting, got all the way through. (After pausing to bale out the trench. Probably got 10 gallons or so in the trench.)

So now we have the 10' RMC riser and 90 out with the conductors stuck inside. From the meter, we were able to pull out the 50' or so of conductors. They're perfect. So we thaw out the rigid until the conductors pull free. Actually some cylindrical pieces of ice come out still frozen to the triplex. Right in the middle of the ice, we could see the nuetral completely squeezed. Almost like you took a dull pair of cutters and were cutting through. The insulation was not damaged, and there was no corrosion. The ice somehow squeezed enough to cut through the nuetral. And the ungrounded conductors looked perfect.

I then cut the 90 at the coupling, and there was still a bunch of ice inside the pipe and the 90. That's in the pic's.

And then matching up the wires to the empty pipe, we figured out that the break occured about 2' above ground in the piece of rigid. Not at the coupling or in the "narrow" part of the 90.

I'd never have believed it if I didn't see it. I almost wonder whether it was a defective conductor from the factory, but figure that's too big of a coincidence to have happened right where it was frozen.

Thanks to eveyone for the replies.

John
 
You have just earned electrician of the month for braving the cold and dealing with that. Looks like a mess. I am sure the small 10 gallon shower was no fun either and I bet temps were not above 20 or 30.
 
Dennis Alwon said:
You have just earned electrician of the month for braving the cold and dealing with that. Looks like a mess. I am sure the small 10 gallon shower was no fun either and I bet temps were not above 20 or 30.
Click to expand...

Thanks. Fortunately one of my guys got the shower. I just laughed and yelled "keep cutting before it fills up".

I don't know about electrician of the month. But if I stayed last friday with the temps what they were, I'd have deserved electrician of the year.:grin:

And BTW the water stunk like hell.:mad:

And I think I'll try out my new duct seal kit from Raychem tomorrow when we finish the job.
 
Thats pretty insane! I'm guessing that you were able to salvage the rest of the run here(pipe). How does that triplex pull in on install? I usually use Cu but sometime Al when price is an issue(dealing with multiple bids).

Tom
 
Davis9 said:
Thats pretty insane! I'm guessing that you were able to salvage the rest of the run here(pipe). How does that triplex pull in on install? I usually use Cu but sometime Al when price is an issue(dealing with multiple bids).

Tom
Click to expand...

Yeah, the rest of the run was fine. Again, I always clean and glue on my undergrounds. The triplex pulls fine. We always use it for residential and so do most around here.

I've seen plenty of undeground services fail, but never one in pipe. At least not one less than 30 - 40 years old. Come to think of it we did an overhead a few months ago to replace a failed underground. But that one was about 50 years old.
 
blue spark said:
Recently we started using 2" flexible carflex as well which seems a better fit for our frost conditions in MN. Frozen 80 will snap like a twig with enough heave pressure.
Click to expand...
Have you considered using HDPE?
 
Status
Not open for further replies.
Top