Broken 3 phase Disconnect - YIKES!!!

[pancho400cid]

I saw the pic below on Linked-In and it made quite an impression on me - thought I would pass it along - I did not find this myself, thankfully......

The pic is a 480 VAC, 3 phase disconnect. If you look, there are micarta hooks that catch a bale on the handle. They pull a spade out and open the circuit for each of the three phases... unless one BREAKS as shown. Note that the spade didn't get pulled for the black wire.

Had the guy who posted the pic on LI just opened the disconnect and gone to work on the downstream equipment - he would have had a very bad day. Wisely, he put a meter on the downstream side of the disconnect as a check, before touching any conductors and found it was still hot.

Depending on what/how the downstream stuff was connected, all three phases could still have been live....

I know a lot of you guys are electricians and know a lot more than I do about electrical work but the pic really drove home the old "check it with a meter first" lesson for me...

 

[RPH]

It's live until you prove otherwise.
Man was smart to verify that's it dead.

 

[Aceman]

This is pretty common failure point in disconnects. I change out several a year for this exact reason.

After seeing this failure as much as I have, it just shows you that you do in fact need to verify EVERY wire is dead, and not just check the closest wire to you and assume the others are dead too.

 

[Toothaker]

Yikes indeed! Thank you for posting this.

 

[wyliesdiesels]

nice.

are u sure its 480v?

those colors are typical for 208Y and 240D....480 is typically brown orange yellow

 

[OccupantRJ]

I visually check each one, every time, check with meter and short to ground with a screw driver before I touch it with the back of my least favorite knuckle.

 

[pancho400cid]

are u sure its 480v?

I thought the guy I took it from said it was 480 VAC... but I am not sure.

 

[zmaxmotorsports]

nice.

are u sure its 480v?

those colors are typical for 208Y and 240D....480 is typically brown orange yellow

Yep,looks like 208 to me also.
People look at the rating on things and automatically go for the highest number.

 

[CheapCharlie]

I visually check each one, every time, check with meter and short to ground with a screw driver before I touch it with the back of my least favorite knuckle.

Don't trust your meter? That sounds like a very bad idea


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[Aceman]

That is not a modern disconnect, I come across a fair amount of older equipment wired black-red-blue that is 480v.

 

[ard]

I was once working in a crawl space on a 50A 240V range circuit an armored cable. Flipped the breaker, until my 120V light that was clipped to one leg turned off down in the hole.

Light off, down into the crawl space ....

Cut the armor short with a hack saw, then firmly grasped one side with the left hand, the other cut off section with the right, sharp twist- crack- then pulled the armor off the end of the wire.

Well. Got as far as the hot wire. Damp crawl, summer in PA, sweaty.

I remember that I couldnt let go- I just fell over, but was still holding on. Then I realized my legs still worked, and I kicked the wire out of my hand.

They say I was screaming the whole time.

That was 40+ years ago.

I will meter or ground the conductors before grabbing them.

 

[wyliesdiesels]

I visually check each one, every time, check with meter and short to ground with a screw driver before I touch it with the back of my least favorite knuckle.

while u could get away with that on a 240v service I would NEVER do that on 480v. You are asking to catch yourself on fire after having a fireball blow up in your face. 480v is not to be messed with like that.

I have never had misfortunes working on 480v knock on wood but have heard plenty of horror stories. One guy told me about a time he was working in a lift high up in a processing plant. The plant couldnt shut down and so he worked a circuit hot(his stupidity) and ended up getting bit by 480v which caused his heart to stop/lost consciousness. Guys on ground had to manually lower lift and do CPR...he couldve died...

There is no telling if the breaker is properly functioning and would be able to clear a ground fault on a 480v line.

Instead of grounding a hot leg, why not use a wire tracer to figure out which breaker its on?

 

[matt_i]

while u could get away with that on a 240v service I would NEVER do that on 480v. You are asking to catch yourself on fire after having a fireball blow up in your face. 480v is not to be messed with like that.

Completely agree. You need a good face shield to keep the molten metal out of your face if you happen to cause a short phase-to-phase...

 

[nadogail]

Electricians are like pilots,
There are old ones and bold ones; old, bold Electricians are very rare

 

[OccupantRJ]

while u could get away with that on a 240v service I would NEVER do that on 480v. You are asking to catch yourself on fire after having a fireball blow up in your face. 480v is not to be messed with like that.

I have never had misfortunes working on 480v knock on wood but have heard plenty of horror stories. One guy told me about a time he was working in a lift high up in a processing plant. The plant couldnt shut down and so he worked a circuit hot(his stupidity) and ended up getting bit by 480v which caused his heart to stop/lost consciousness. Guys on ground had to manually lower lift and do CPR...he couldve died...

There is no telling if the breaker is properly functioning and would be able to clear a ground fault on a 480v line.

Instead of grounding a hot leg, why not use a wire tracer to figure out which breaker its on?

I never work on anything above 240 volt. Our plant is 208 three phase and is fairly old. Some previous wiring and methods are questionable to say the least. Grounding is done after meter tests and known protection devices are open, not to find the circuit protection.

 

[sberry]

I turned the wrong breaker off, worked on it an hour, did the repair, went to turn it on and figured it out. Done that a couple times over the years.

 

[TractorJeff]

Yeah a screwdriver across a 100 amp fuse will blow up in your face before the fuse blows!
Better to meter by following proper Testing procedures.
Check meter on known live circuit.
Test Circuit in question.
Check meter on known live circuit to validate.
Attach grounding jumpers!

When we are suited up and going into a huge breaker/metering cabinet. We dang sure want to know the meter works and the circuit we are servicing is truly dead!

BTW: Ive seen the same issue with damaged disconnects! Pretty common!

 

[steve0xr]

I work up to 230kv. Everytime we touch something it is tested live-dead-live, meaning test a known hot source. Test your dead circuit. Then test a known hot source again. This ensures your circuit is dead and your meter is working properly.

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[Duck tape Bill]

I work up to 230kv. Everytime we touch something it is tested live-dead-live, meaning test a known hot source. Test your dead circuit. Then test a known hot source again. This ensures your circuit is dead and your meter is working properly.

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This!!!...

I do basically the same thing even working around the house on 110v. It takes the same amount of time to check as it does to electrocute yourself, so why not?

 

[alfredeneuman]

nice.

are u sure its 480v?

those colors are typical for 208Y and 240D....480 is typically brown orange yellow

On 240 Delta 3Ø the stinger (208 volts to ground) is required by Code to be on the "B" phase and be marked Orange. (Except in San Francisco where the color required is Violet) :supergay:

 

[sberry]

My bud said he was in another country, turned off the disconnect that was piped to the machine, crawled under it, working by himself and proceeded to unhook it and wham, when he came to figured this was the end under a machine in a shithole south American country.
Seems it was old **** and someone had put the actual one on the other side of the wall.

 

[APEowner]

I keep a non-contact voltage tester in my tool belt and try to remember to verify that a circuit is dead before I got to work but it's good to have a reminder. Also, if using a non-contact remember to test it on a live circuit before trusting it. I've been bitten by that one.

 

[wyliesdiesels]

On 240 Delta 3Ø the stinger (208 volts to ground) is required by Code to be on the "B" phase and be marked Orange. (Except in San Francisco where the color required is Violet) :supergay:

While the stinger is required by code to be orange and on the b phase i have seen it colored all sorts of different colors and on the a phase or c phase.

 

[alfredeneuman]

While the stinger is required by code to be orange and on the b phase i have seen it colored all sorts of different colors and on the a phase or c phase.

The power companies typically supply it on the "C" phase.
It's left up to the contractor to transfer it to the "B" phase at the first place possible .

 

[rlitman]

nice.

are u sure its 480v?

those colors are typical for 208Y and 240D....480 is typically brown orange yellow

That's what I was wondering. Also, all of the 480 disconnects I deal with have arc chutes around the contacts. The 208 stuff does not.

That is not a modern disconnect, I come across a fair amount of older equipment wired black-red-blue that is 480v.

Could be that. The lack of arc chutes and use on 480 would explain why one leg welded itself shut.

 

[wyliesdiesels]

The power companies typically supply it on the "C" phase.
It's left up to the contractor to transfer it to the "B" phase at the first place possible .

That must vary by PoCo.

Around here the stinger is always on thr B phase. However, I always check to make sure. I dont need a bad day with fried 120v equipment.

However, on an overhead drop, it would be the electrician and how he hooks up the service entrance that would distinguish the phases.

On an underground lateral its obviously the PoCo that would make the connections...

Our local PoCo doesnt provide new Delta at all anymore and I think PG&E is the same....

 

[Norcal]

That must vary by PoCo.

Around here the stinger is always on thr B phase. However, I always check to make sure. I dont need a bad day with fried 120v equipment.

However, on an overhead drop, it would be the electrician and how he hooks up the service entrance that would distinguish the phases.

On an underground lateral its obviously the PoCo that would make the connections...

Our local PoCo doesnt provide new Delta at all anymore and I think PG&E is the same....

In a 7 jaw meter can the high leg is in the C phase as the meters are set up that way.

 

[wyliesdiesels]

In a 7 jaw meter can the high leg is in the C phase as the meters are set up that way.

Aww ok.

I havent memorized all the different meter jaw configs...

 

[toplessHO]

yep look at meter base
most have an offset on C phase
for high leg

 

[zmaxmotorsports]

Electricians are like pilots,
There are old ones and bold ones; old, bold Electricians are very rare

Hold my blended strawberry margarita, I'm going in.

 

[zmaxmotorsports]

On 240 Delta 3Ø the stinger (208 volts to ground) is required by Code to be on the "B" phase and be marked Orange. (Except in San Francisco where the color required is Violet) :supergay:

 

[PCustoms]

Have to dig up a pic of the one that failed on me 2 years ago...

Went to shutdown some backup equipment at end of day, could feel the heat coming off the can. Got my head electrician who gingerly opened the disconnect.

4" of melted insulation, plastic internals cooked to a crisp and the mounting screws so hot the burned out of the plywood wall. Had I grabbed it and pulled rhe switch like you normally would I would have pulled 2 energized legs right into the door and caught the resulting arc flash right in the face from a foot away.

 

[Norcal]

This is a photo of a A/C disco that had been rendered useless.



Supply is 208V 3Ø, unit is 1Ø.

 

[canbug]

A couple of things
1, It's not dead until you have metered it. It was stated earlier, Test your meter on a live source first, then test for dead, and back to the live source to confirm your meter is working correctly.
2 Electrons, voltage, don't care what color the wire is.

Better Safe Then Toasted.

Tim.