Damaged 600 amp feeder repair

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Dannyboy1978

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Location
NY
Hi All,

First time posting but life long viewer and supporter of MH and site.

Project we are doing down in St. John USVI, The excavator/GC damaged the existing 600 ampere feeder conduit that was on premises.

The existing 120/240 single phase feeder was piped/installed(not by us) with 3 sets of 3/0 in 1 X 4" PVC conduit fused @ 600 Amps @ 250 feet. The damage was done on 1 of the sets on the phase side.

We are discussing options for repairs and I would like to hear from some other professionals.


My first option was:

  • Shunt out the damaged conduit allowing us to work and open trench as necessary. We can then remove and abandon old conduit and feeders. Re pipe 2 X new 3 or 4 inch PVC conduits. Install 2 new sets of 500 Mcm feeders.
My second option was:
  • Shunt out the damaged conduit. Remove damaged section of conduit/feeder. Try and remove the existing 3/0 feeder. Repair existing 4 inch conduit as needed. Pull 2 new sets of 500 mcm in existing 4 inch conduit. I'm concerned with the integrity or this conduit and not sure if its been damaged anywhere else. Plus the pull will be a bear.
My third option was:
  • Cut back on shorter section of feeder. Have GC install property box. Re pipe into a proper splice box. Pull new sets of 3/0 cable on the shorter side and splice accordingly.

A couple of points on option 1/2: I'm up sizing to the 500 mcm to accommodate for the length of run and lower the voltage drop.

The last option which I told contractor I advised against and wouldn't do is:
  • The contractor wants to do a direct burial splice on the cable and try and rebuild the conduit using resin, pipe etc. I'm totally against this as the THWN/XHHW wires inside damaged conduit are not listed for direct burial.

I've attached some pics.

Thanking you guys in advance.

IMG_2936.jpgIMG_2931.jpgIMG_2934.jpg
 
The NEC way would to pull out all the conductors and at a minimum replace the damaged ones. Meg everything.

I would lead with replacing it all, because it doesn't work very well to remove wire, roll it up or stage it, and pull it back in. While replacing only the wires that were damaged.

I can tell you out here in farm country on LONG pulls(250' isn't considered long over here), we have spliced with compression buttsplices and adhesive lined heatshrink damaged wires.

We follow it up with a clamshell kit from these guys with some stainless hose clamps to keep it secure.

http://www.ipexna.com/usa/products/electrical/rigid-pvc-conduit-fittings/epr-repair-kit-for-conduit
 
I would say your options suck. You can't fit 3 sets of 500 KCMIL in the conduit, but I think you might be referring to two sets of 500 (don't forget to upsize your ground) This, is actually required to comply with derating per 310.15(B)(3)(a). The original installation was a violation of code. If you are trying to comply with code, then pull it out, repair the conduit and pull new conductors in. If you aren't trying to comply with code, then repair the conductor and conduit per Cow. We (well I) won't tell.

I wouldn't worry too much about the rest of the conduit, but if you have access to a mandrel https://www.zoro.com/greenlee-4-inc...Twa2UNCpI85zI_rAKUzNgERUejJ4P_X4aAvjjEALw_wcB pull it through fist. Don't forget to tie a rope on both ends in case it does actually get stuck in the conduit.
 
is there any chance the conductors are of a type that is allowed to be direct buried? is so you might be able to just repair them in place and not worry about the trying to repair the conduit.
 
Thx guys for the info so far. Appreciated.

I agree the original install was in violation. We came on to clean up after the orginal EC and we pointed it out.

Yeah the cable is THWN/XHHW as far as I can see not rated for direct burial.

If they go with the proper fix we will definitely try and get the conduit cleaned with the mandrel.

Thx again.
 
classic pandoras box.

-whoever was at the controls is paying the bill. start ignoring the Gc (controler) immediately and do it right... unless blue stake is on the hook.

-there is nothing wrong with re using undamaged conductors but lenght may be an issue. like strat said, id fix and re use damaged conduit and bring up to code with added conduits... the cheap always costs more in the end. (so many wrongs here- the first being, who runs feeders in a footing?) and it looks like a new house, no? how the heck did he not know it was there?

-another great reason (regardless of your trade or scope of electrical) to have in your contract, All existing work is hereby assumed blah blah blah UP TO CODE, if not owners assume all costs regardless blah blah blah TO FIX existing violations.

-be sure to have your lawyer re-word that last bullet point. :)

edit- ok, it may be the wall footing or better, just slurry... but yeah,,,, why slurry crap work, and second well duh, because a track hoe operator doesn't stop when he hits rocks. so there is that answer
 
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Strathead said:
I would say your options suck.
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The GC won't be happy but it's better just to redo the whole thing and do it right and that way you can walk away with a clear conscience and sleep nights. They should have known better than to get close to conduit like this with any sort of excavator.
 
You have three existing conduits. Only one is damaged.

I can't think of any reason not to pull the conductors out of the damaged conduit and repair it and then run new conductors into the repaired conduit.

I can't think of a good reason to run bigger conductors unless there is a problem with VD.
 
petersonra said:
You have three existing conduits. Only one is damaged.

I can't think of any reason not to pull the conductors out of the damaged conduit and repair it and then run new conductors into the repaired conduit.

I can't think of a good reason to run bigger conductors unless there is a problem with VD.
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Thx Bob,

Other conduits are for Fiber to ISP and other does gate controls. They are all grouped together. Yes the bigger conduit would address the VD since run is at 225 ft.
 
Dannyboy1978 said:
Thx Bob,

Other conduits are for Fiber to ISP and other does gate controls. They are all grouped together. Yes the bigger conduit would address the VD since run is at 225 ft.
Click to expand...

I thought your OP meant there were three separate conduits the power wires were installed in.I was not paying close enough attention to what you typed. So they have nine 3/0 wires and a ground in one conduit?

I can see your dilemma better now.

Any reason you can't just run UG cable?

What is the calculated load? If it is THWN-2 wire you could replace the 600A fuses with 500A fuses which would appear to make you compliant if the calculated load supported doing so.
 
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You would have thought when the operator hit the buried cable marker they would have investigated, why no labor watching him dig, I know.
With the above in mind put it in new and make some money, remember scrap probably goes to the payer now days so no discounts.
Worked for a guy who pulled feeders from one job had us pull them in on another never meg them, boom, must be the men fed up.
If your work burns part of the house could you just buff it out?
 
How far from the end of the conduit is the damage? Could you not replace the damaged phase conductors with 2 sets of 350cu possibly utilizing the damaged conductors as your pull rope. Utilize the 3 sets of 3/0 as your neutral conductor, and 1 of the remaining 3/0 as the egc. Original conductors copper I assume
 
Cow said:
...
I would lead with replacing it all, because it doesn't work very well to remove wire, roll it up or stage it, and pull it back in. While replacing only the wires that were damaged. ...
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Amen to that. The only time I have been in an Arc Flash incident was when conductors were pulled out and back into a conduit; the insulation was nicked and missed in the megger check, which was done prior to terminating (so the conductors were moved again after being meggered). It's a high risk situation for further failure.
 
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