This is why we disconnect and test

David G · Jan 10, 2017

One of my vendors posted this picture.

Janicholson · Jan 10, 2017

That is nasty. A little fibrous looking trash and full rated amps makes heat and heat welds. Jim

Geo-TH,In · Jan 10, 2017

Like I've posted in past, test then verify by using two screwdrivers and shorting out wires to ground.

Steve@Advance · Jan 10, 2017

I've seen the exact same thing! Horrible design!

Bret4207 · Jan 10, 2017

(quoted from post at 14:49:36 01/10/17) Like I've posted in past, test then verify by using two screwdrivers and shorting out wires to ground.

I'll stick with my tester thanks...

Ken Combs · Jan 10, 2017

Me too! much preferable compared to arc flash!

John T · Jan 10, 2017

DITTO At our facility we had to preform a complex maximum short circuit current analysis and found as high as near 10,000 Amps could potentially flow through a low impedance "short circuit" and that can create some serious big time arcing and heat and extreme bright flashes YIKES and besides if a circuit breaker wasn't sufficiently rated (most however are 10,000 AIC) even more YIKES

John T

Chilidawg · Jan 10, 2017

(quoted from post at 20:33:29 01/10/17)

(quoted from post at 14:49:36 01/10/17) Like I've posted in past, test then verify by using two screwdrivers and shorting out wires to ground.

Click to expand...

I'll stick with my tester thanks...

bsolutely!

Geo-TH,In · Jan 10, 2017

JohnT,

After getting a handful of 440vac, I'll always do the arc test after using a meter and I'm still kicking. A big flash always stimulates the heart just a little, don't you think?
geo

John T · Jan 10, 2017

George "A big flash always stimulates the heart just a little, don't you think?"

Having seen plenty I THINK INDEED IT DOES but its a flash I don't like to experience

John T

Geo-TH,In · Jan 10, 2017

JohnT, Sometimes when you know when there will be a big bang it can be fun.

If you know a capacitor is charged and you use a piece of solder and insulated needle nose to hold the solder to discharge cap, It will produce a big flash and bang. That's exciting. Try it. May want to wear safety glasses, solder gets vaporized.
geo

DENNIS MIN · Jan 10, 2017

David G,

I was witness to an experienced electrician. I saw him test phase to phase on the input of a transformer..zero volts.

He then checked phase to ground and had 277vac. It turns out that the three pole breaker failed to opena phase, the transformer had a delta primary winding. Had he not been thorough, he'd been shocked in front of me.

D.

I learned my lesson by proxy.

old-9 · Jan 10, 2017

GREAT Photo!! Just proves that anything can and will malfunction at one time or another. The most used tool on my tool belt was my voltage tester. I would guess it saved my life or at least saved me from a shock or two. I was taught to test for voltage first, then check the tester on a known voltage just to be sure the tester STILL worked. Kept me alive for 40 years. joe
tester

JMOR · Jan 10, 2017

Don't let 'em beat you up too much, Geo, as those who work truly HV will do all the measuring & checking that is possible, but before touching, they will hang a grounding stick on it. Always looked right to me & so far haven't seen one dead.

Steve@Advance · Jan 10, 2017

I learned a hard lesson shorting 120v to trip an unmarked breaker.

It was in an industrial plant, in operation, didn't want to start turning off breakers, disrupting work.

This circuit was in a storage area above the offices. I grounded the hot lead, it killed the circuit, but didn't trip the breaker!

After 2 days searching, found a hidden junction box, behind the sheetrock. It had blown apart a bad connection...

I don't do that no mo!

jeffcat · Jan 10, 2017

You bet! I start by rubbing my line tick on my sleave. Trilllll..Next
i pull out the meter. Some of the dish machines have TWO power
supplies. 240 3phase or 480 3phase. The secondary suply is 120 volt
for the control systems. Kinda bites ya if you forget about that
120!!! Have gotten popped a couple of times.

pete black · Jan 10, 2017

Precisely why acb's (air circuit breakers) are not used as clearance points as their contacts cannot be seen to verify "open".

Texasmark1 · Jan 10, 2017

Yepper!

Jaden · Jan 10, 2017

I have had that happen twice, both in outdoor applications. Fortunately, I checked phase to phase and each phase to ground. I may also double check with a volt stick.

Russ from MN · Jan 10, 2017

I got the job one time of cutting holes in the doors of switchgear and putting plexiglass over them so we could verify the switch was disconnected. Once we had locks on the handle you could no longer open the door to verify.

n9lhm · Jan 11, 2017

"If it ain't grounded, it ain't dead". I've done a lot of work on high powered AM broadcast sites and metal in a high RF field picks up enough energy to shock and burn you even when it's disconnected.

This is why we disconnect and test

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