sort of a bolted fault short.... sort of.

[Fulthrotl]

customer of mine has a marina. still does, lucky man.
it didn't burn to the waterline.

the other day, there was a bolted fault short inside a 2" GRC
conduit feeding one section of marina. harbor patrol noticed
smoke, and could see what looked like a signal flare burning
on the dock, visible from 100 yards away.

wooden dock, with pretty much full occupancy. lotta boats
tied up, some with live aboards.

seems a 3/0 copper feed with kearneys tapped off in 2" T's
went to ground, welded itself there, and as there wasn't a
good enough ground path to fault the 200 amp fuse and open
the circuit, just sat there burning. the resistance at the couplings
from rust got them hotter than the other parts of the pipe, and that
is where some of the flames were coming from. it seems that the
split bolts were taped with what looks like 79 cent plastic tape,
witout rubber tape or varnished cambric, and the high current flow
started melting them in the condulets working their way back to the
panel. as they began shorting out, it provided a better path to ground,
and finally enough current flow occurred to open the cartridge fuse.

it would seem that new conduit, wire, and dock boxes are in order.
awaiting communication from the owner about what course of action
he wishes to take.

here is the bolt at fault:





here are some more photos of the conduit condition:

 

[GoldDigger]

Isn't it nice that the raceway is legally capable of carrying whatever fault current the hot wires can deliver?

Tapatalk!

 

[augie47]

Please tell me it was never inspected

 

[GoldDigger]

Never mind....

Tapatalk!

 

[Fulthrotl]

Please tell me it was never inspected

ok. it was never inspected. did that help?

 

[RLyons]

Taped split bolt....not a fan
Come across a few that have a worn spot where the bolt was making contact with a jb cover.
And one time at band camp had a panel cover I was removing blow up cause of split bolt.

 

[J.P.]

Every split bolt I have came across has needed to be replaced.

I'm not sure how good polaris lugs will be long term, but right now they seem a lot safer than split bolts.

 

[texie]

ok. it was never inspected. did that help?

Forgetting the code violation here, one would have to wonder what kind of magician it would take to get those connections made in that conduit body.

 

[gadfly56]

Forgetting the code violation here, one would have to wonder what kind of magician it would take to get those connections made in that conduit body.

Pull enough slack to make the connections outside the body, then pull on the other ends to draw the whole mess back in. Not that I know from personal experience, you understand...

 

[mivey]

Every split bolt I have came across has needed to be replaced.

Similar to always finding something in the last place you look.

I'm not sure how good polaris lugs will be long term, but right now they seem a lot safer than split bolts.

I've installed untold numbers of them and never had a failure that I know of. Even re-worked some troughs that my boss had put in long before I was born and they were still in perfect shape when we took them apart. There is a right way and wrong way for everything.

 

[cowboyjwc]

Similar to always finding something in the last place you look.

I've installed untold numbers of them and never had a failure that I know of. Even re-worked some troughs that my boss had put in long before I was born and they were still in perfect shape when we took them apart. There is a right way and wrong way for everything.

And a right place and a wrong place. Forgetting some of the other violations, take a taped splice and put it in a metal box on a platform that moves up and down, all the time, and you're going to have an issue. We had the same thing happen on a train platform. The splices were done simply with rubber tape in in ground boxes. Pretty soon the vibration of the platform from the trains wore through the rubber tape, and someone stepped on the metal cover and grabbed the hand rail at the same time and you can guess what happened. No they were not inspected (don't ask).

 

[kingpb]

For gods sake, use a new conduit system that isn't going to rust away.:slaphead:

 

[mivey]

And a right place and a wrong place.

I agree with that.

Forgetting some of the other violations, take a taped splice and put it in a metal box on a platform that moves up and down, all the time, and you're going to have an issue. We had the same thing happen on a train platform. The splices were done simply with rubber tape in in ground boxes. Pretty soon the vibration of the platform from the trains wore through the rubber tape, and someone stepped on the metal cover and grabbed the hand rail at the same time and you can guess what happened. No they were not inspected (don't ask).

Consider that a bad abrasion condition will also wear through the conductor insulation or the coating on a Polaris connector. Wrapped and positioned correctly, the abrasion withstand should hold up as well as the conductor insulation or the Polaris insulation. You really have to watch the sharp edges with the split bolts and I'm sure many do not take the time to provide adequate coverage. Back in the day split bolts were all you had so you had better make them work right.

The value of split bolts is greatly reduced if a Polaris will do the job since it is so much easier, faster, and versatile. I can also imagine wrapping a Polaris would be wise for some installations.

 

[mivey]

For gods sake, use a new conduit system that isn't going to rust away.:slaphead:

But PVC won't get you that nice EGC.

 

[Fulthrotl]

Forgetting the code violation here, one would have to wonder what kind of magician it would take to get those connections made in that conduit body.

like was said... pull a little loop out, make 'em up, push them back...
go down the whole run doing that.

the simplest fix is to use 2" schedule 80, with FA's and chase
nipples entering the sides of the dock power pedestals, and pull
3/0 aluminum, fusing appropriately. now... as i'd be running
the 2" on strut on the dock, would i have to derate like i would
if i was running across a roof?

3/0 AL is only good for 103 amps 2" off the roof.
without derating, it's good for 150 amps.

 

[don_resqcapt19]

...
The value of split bolts is greatly reduced if a Polaris will do the job since it is so much easier, faster, and versatile. I can also imagine wrapping a Polaris would be wise for some installations.

But you would never fit the Polaris in that T fitting

 

[don_resqcapt19]

... as i'd be running the 2" on strut on the dock, would i have to derate like i would if i was running across a roof? ....

While the conditions and heating are likely much the same as on a roof, the rule in 310.15(B)(3)(c) only applies to conduit or cables exposed to sunlight on rooftops.

 

[kingpb]

Depending on the length of run, you may have to take into consideration thermal expansion of the conduit. Seen more than one run buckle under increased temperature.

Funny, someone said install PVC on strut. Sort of defeats the whole purpose of the PVC, when after the strut rusts away, the PVC just falls to the ground/dock.

 

[mjf]

Forgetting the code violation here, one would have to wonder what kind of magician it would take to get those connections made in that conduit body.

That's probably one reason there was no rubber tape....too bulky.:slaphead:


I'm not a fan of split bolts either. When I do use them, first they become a ball of duct seal, then rubber taped, then electrical taped.

 

[Cow]

Depending on the length of run, you may have to take into consideration thermal expansion of the conduit. Seen more than one run buckle under increased temperature.

Funny, someone said install PVC on strut. Sort of defeats the whole purpose of the PVC, when after the strut rusts away, the PVC just falls to the ground/dock.

I saw no mention of strut type, I would assume a guy would use stainless or fiberglass strut in a marina. I'd also wonder how long aluminum wire will last that close to water as well?

The real problem I see is running pvc on strut while allowing the pipe to expand by using the right straps as well as keeping it from breaking in between supports by people trying to balance on it with all their weight. Instead of strut I might lean towards some sort of stainless 2 hole strap either a little oversized or with a stainless washer underneath to reduce the grip and allow expansion. At least if someone stood on it, it wouldn't bow between supports.

I have no doubt that whatever Randy comes up with it'll be much better than before.