One event, more than one fault

[chris kennedy]

I got hurt yesterday in a a one in a million event. I got a call to stop on my way home and check sparks in an AHU. When I got there I pulled out the disco pullout and got a ladder to inspect the units.

As I climbed up I grabbed the allthread supporting the units then grabbed the copper lines and got hit so hard I could't let go. Seemed like 5 seconds before the ladder and myself hit the floor.

Tester showed 210V between the copper and the allthread. High leg fault right?

There where a number of disco's at the service. The building is 40 years old and high leg is on C. Turned off one at a time untill fault clears. Disco in question was 3? but used as single phase, A and C hooked up.

Pulled out C and capped it off.

Put AHU pullout back in disco and show no volts allthread to copper. I put one prong of tester in a near by rec neutral slot and find allthread clear but 120V to copper.

I opened unit to find all kinds of wire lying in the bottom not capped off. Some genious disabled the heat strips by pulling one conductor off each and left them touching the unit. Cut and capped those.

Heres something puzzling. In the AHU's if you test from each lug to the EGC you get 120V. Why didn't the fault/faults clear? I also tested each lug to allthread and nothing. Tested continuity between allthread and EGC and had nothing.

I'm sorry I didn't think about pics untill I got home.(I was a little shaken up) I need to go back tomorrow so I'll get some.

 

[r_merc]

Wow. That is a scary story to me. I don't know you but glad you survived.

Rick

 

[frizbeedog]

I got hurt yesterday in a a one in a million event.

Heres something puzzling.

......Like, I'm sure you'd like to meet the dumbass who nearly got you killed.

And that would suck for all of us, and everyone else who knows you, because we really like you chris. :smile:

When you figure it all out please update us, because I wan't to know too.

Best wishes.

Murf.

 

[mxslick]

Heres something puzzling. In the AHU's if you test from each lug to the EGC you get 120V. Why didn't the fault/faults clear? I also tested each lug to allthread and nothing. Tested continuity between allthread and EGC and had nothing.

The answer is in that last statement. Since there was no continuity to the EGC and the alltread, no return path for the fault until Chris was unfortunate enough to provide one with his body.

But, I just noticed something interesting in the first part of this statement:

In the AHU's if you test from each lug to the EGC you get 120V.

Was this test with a digital meter or a wiggy? Either way it sounds like there's a problem with the ECG downstream since it did not allow enough current to pass to clear the fault.

And if you do find the person who left all those heat strip wires loose, may I suggest a retaliation?

 

[chris kennedy]

The answer is in that last statement. Since there was no continuity to the EGC and the alltread, no return path for the fault until Chris was unfortunate enough to provide one with his body.

But I can't for the life of me see how the allthread got energized. I need to recreate the event.

But, I just noticed something interesting in the first part of this statement:

In the AHU's if you test from each lug to the EGC you get 120V.

Was this test with a digital meter or a wiggy? Either way it sounds like there's a problem with the ECG downstream since it did not allow enough current to pass to clear the fault.

Digital, but why didn't enough currert flow to burn whats left of the EGC?

And if you do find the person who left all those heat strip wires loose, may I suggest a retaliation?

No thanks.

 

[Pierre C Belarge]

Chris
I am glad to see you are okay. I am sure that you may have more than been a little startled. It is also good to see one of the more active members be able to show that we are all human and can make some horrible mistakes.

With that said, it is with a cavalier attitude that most electricians I see everyday go to work, shirking the thought that they may get hurt/killed. Each and everyday the evade an incident helps to make them a little more careless.

I have seen such horrible work, that I carry a volt tic with me everyday. When I have to squeeze by equipment, I volt tic it first. That may not be foolproof, but it is an attempt.
Twice I have used the volt tic and found live enclosures...


Good luck Chris and all of the others who frequent this site.

 

[frizbeedog]

....I need to recreate the event

Without the whammy and the falling off the ladder part I hope.

 

[mdshunk]

Were these heat strips on some other disco that you didn't disconnect?

If I'm reading right, you pulled out the disco, but got zapped anyhow. You attributed that to the bare conductors inside the AHU. How were they energized if you had the pullout pulled out?

 

[chris kennedy]

Were these heat strips on some other disco that you didn't disconnect?

If I'm reading right, you pulled out the disco, but got zapped anyhow. You attributed that to the bare conductors inside the AHU. How were they energized if you had the pullout pulled out?

I didn't have the heat strip fault (120V) with the pullout open. I had the 210V allthread. That was the shocker.

 

[mdshunk]

I didn't have the heat strip fault (120V) with the pullout open. I had the 210V allthread. That was the shocker.

Gotcha. There's a fault someplace else, which you are going to pin down Monday. You had one leg faulting in the unit, and the high leg faulting potentially anywhere in the building. This should prove interesting.

 

[frizbeedog]

.....I got a call to stop on my way home and check sparks in an AHU.

I'm glad you brought this up chris...and in the saftey category for one.

When I get a call for equipment acting up as you describe, I'm extra cautious. My routine is going in slowly, wearing gloves an glasses at a minimum. Given the fact that we have a known funky condition we have to be cautious and take our steps slowly and carefully and be on our guard. Elevateted on ladders, even more so.

It happens without warning and for reasons that are generally out of our control. When we are called, something has gone wrong.

Sometimes we don't get the luxury of having a bad day.

 

[chris kennedy]

Gotcha. There's a fault someplace else, which you are going to pin down Monday. You had one leg faulting in the unit, and the high leg faulting potentially anywhere in the building. This should prove interesting.

This is correct.

After we cleared the Hi-Leg fault and energized the AHU's we found the 120V fault. Again after that was cleared I was reading 120V from each lug to the EGC. Why didn't the fuse blow or the EGC burn through?

Sounds like a job for a megger but neither my company nor myself own one.

 

[JohnJ0906]

Maybe the resistance of the heat strips kept the breaker from tripping. You would still have voltage, but not enough current to open the breaker.

Chris, glad to hear you are (relatively) OK.

 

[mdshunk]

Again after that was cleared I was reading 120V from each lug to the EGC. Why didn't the fuse blow or the EGC burn through?

My guess is that the fault is resistive enough to probably be below the value of the OCPD.

 

[Chamuit]

Glad you're okay. Don't ever want to hear that anyone didn't make it home.

 

[Dennis Alwon]

Chris don't die on me buddy> I would lose a good friend.

Is the allthread isolated. I am a bit confused. Was the current on the copper line or the allthread. Your first post suggest the copper line had the current.

 

[mdshunk]

Sounds like a job for a megger but neither my company nor myself own one.

I honestly don't think you need one in this case. The fault already shows up with a regular meter (or your hand!).

 

[chris kennedy]

Is the allthread isolated. I am a bit confused. Was the current on the copper line or the allthread. Your first post suggest the copper line had the current.

The allthread is supporting the pan under the AHU's and not in contact with them. This was energized by the high-leg somehow. The AHU was energized by one of the 120V legs.

 

[mdshunk]

The allthread is supporting the pan under the AHU's and not in contact with them. This was energized by the high-leg somehow. The AHU was energized by one of the 120V legs.

Whatever the allthread's screwed into (piece of strut in common with other stuff, metal pan deck, etc) is probably energized by something. Wouldn't that be something if an entire metal deck was energized?

 

[nakulak]

so glad you are ok. be safe.