Short circuit protection using PVC pipe??

[milemaker13]

So, just want to hear some comments on the subject. While the guys were cutting concrete for a new machine pad, they cut thru seven pvc pipes containing everything from low volt fire signals to 277 lighting loads and lots of 110 in between.

So when they cut, a 1200 amp breaker tripped, but this is ahead of a 200a main and also indivudal breakers.

That breaker was reset and it held in. Most of the 110 breakers were tripped too, but not all. The most worrisome was the 277v line that did not trip. Just sat in the pipe burning away. WTF?

So, in steel pipe it would have most likely tripped... but what about the PVC?

As I type, and think it over..... Im still confused I guess... And of course I've got everyone and their brother in the hole asking dumb questions. Thats not helpful:huh:

FYI- We're all fine and its now under control. Just looking to hear some comments. Thanks guys!

 

[jim dungar]

The most worrisome was the 277v line that did not trip. Just sat in the pipe burning away.

The absolute worst fault to have is one at 277V, it is just as likely to continue arcing and burning as it is to trip a protective device. This is why, for the past 40 years, the NEC has required Ground Fault Protection (GF not GFCI) on some 480Y/277V circuits.

 

[ActionDave]

The absolute worst fault to have is one at 277V, it is just as likely to continue arcing and burning as it is to trip a protective device. This is why, for the past 40 years, the NEC has required Ground Fault Protection (GF not GFCI) on some 480Y/277V circuits.

No doubt. And to add to the point, I have a brother in law who is a lineman for quite some time. Out of all the voltages he deals with he also says 480/277 is the worst.

 

[Stevareno]

Combine that with the old style Federal breaker, and you've got one heck of a welder.

 

[milemaker13]

Sounds like the newer 1200a main (480v) tripped due to the ground fault protection it has. That is the only thing that makes sense (to me, for now any how:blink::ashamed1::?)lol.

Yeah, it was the worst feeling of all not knowing where the line came from. Looked like cannon fuse burning inside the pipe. Wasn't much I could do except start flipping breakers from "that direction" . Geeze, talk about Pro trouble shooting.

Anyway, ive got some pipes to splice and repull. Thanks guys! Hey, happy Holidays!!:thumbsup:

 

[mgookin]

... While the guys were cutting concrete for a new machine pad, they cut thru seven pvc pipes containing ...FYI- We're all fine and its now under control. Just looking to hear some comments. Thanks guys!

It really took that many for them to figure it out?

I guess if you're running a big diamond wet saw through concrete and steel reinforcement, a little bit of pvc and copper may actually be easier cutting. I would guess it was the fireworks that got their attention, or loss of power to their saw.

Glad everyone's ok. Sounds like you're in good shape now. Maybe there's a way for better planning in the future if they change out or add more machines.

 

[milemaker13]

No fireworks at all. Just darkness. I wish I could have the floor x rayed each time, but that aint never gonna happen. We used the tracer and all, but its not the magic wand everyone thinks it is. If you arn't actually hooked to that particular pipe/wire it wont show up. And the bleed thru with the rebar is crazy.