# Disconnect operation and arc flash.



## Wirenuting

MDShunk said:


> Is the operation of a sidearm disconnect, with the door closed, the type of interaction with electrical equipment that would require arc flash protective clothing to the level specified on the arc flash survey label?


With only this information provided I would say yes. 

It could be an old disconnect your standing at with a new arc flash calculation posted. 

If it's a new disconnect I would say with the door closed the calculation is posted for work performed with the door open. 
Modern equipment is designed to contain the fault inside the can. That's why you don't need to dress up just to reset a breaker with the cover properly in place. 

Just my take on it.


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## MDShunk

Wirenuting said:


> With only this information provided I would say yes.
> 
> It could be an old disconnect your standing at with a new arc flash calculation posted.
> 
> If it's a new disconnect I would say with the door closed the calculation is posted for work performed with the door open.
> Modern equipment is designed to contain the fault inside the can. That's why you don't need to dress up just to reset a breaker with the cover properly in place.
> 
> Just my take on it.


This old disconnect/new disconnect language doesn't seem to exist in 70E.


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## McClary’s Electrical

I would say no, and partly the reason some manufacturers extend the overloads reset mechanically flush with door, to eliminate need for opening door.


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## MDShunk

mcclary's electrical said:


> I would say no, and partly the reason some manufacturers extend the overloads reset mechanically flush with door, to not eliminate need for opening door.


Yeah, but that overload reset on the outside existed 50 years or better before anyone ever thought about arc flash safety.


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## Wirenuting

MDShunk said:


> This old disconnect/new disconnect language doesn't seem to exist in 70E.


I understand what your saying & I don't have 70E here with me at work. 
But we don't do arc flash calculations here. I just look at 60 year old gear and keep in mind that modifications have been made to our systems and that new hazards are present. Newer gear is designed, I believe, to contain the fault within the enclosure. 
An old bulldog building disconnect now use to feed 480 is above what its original installation is designed for. 
I just take greater care around the older gear.


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## Wirenuting

mcclary's electrical said:


> I would say no, and partly the reason some manufacturers extend the overloads reset mechanically flush with door, to not eliminate need for opening door.


But what if the starter is old and the "replacement" contactor-overloads do not match up to the reset?
We have changed the internals and left the can. Besides loosing the listing we have created the need or desire to open and reset it. 

Poof is the word.


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## MDShunk

I disagree that gear is designed to contain the arc blast. Study after study has shown covers launched at a hundred miles an hour. Even the so-called arc safe switchgear doesn't contain the arc blast. They have those dotted plates on top that blow off and shoot the blast straight up. 

I found somthing:

_FPN No. 1: An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. ....
_

When operating a disconnect, one never knows if that operation of the handle you are about to perform may cause something to break and go phase to phase.


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## McClary’s Electrical

MDShunk said:


> Yeah, but that overload reset on the outside existed 50 years or better before anyone ever thought about arc flash safety.


 
Yes, but they're still made that way. IMO, a person does not need the same level of PPE to push that reset or close the disconnect, as he would to open the enclosure.


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## MDShunk

mcclary's electrical said:


> Yes, but they're still made that way. IMO, a person does not need the same level of PPE to push that reset or close the disconnect, as he would to open the enclosure.


I have opinions too. They match up with yours pretty well. 

What I was looking for, mostly, is where it might be spelled out a little better in black and white. What I'm afraid of is that my opinion (and yours) does not match up with the model standard.


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## Wirenuting

MDShunk said:


> I disagree that gear is designed to contain the arc blast. Study after study has shown covers launched at a hundred miles an hour. Even the so-called arc safe switchgear doesn't contain the arc blast. They have those dotted plates on top that blow off and shoot the blast straight up.
> 
> I found somthing:
> 
> FPN No. 1: An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. ....
> 
> 
> When operating a disconnect, one never knows if that operation of the handle you are about to perform may cause something to break and go phase to phase.


That's a good statement. Makes me think even more. Plenty of time I see old gear break when operated correctly. It normally just leaves a leg energized,, but that's not your point. 
So your correct that gear can break and flash during normal operation. Even if we are not doing something that can "cause" an explosion. 

But then we think,, who needs PPE to reset a breaker? 
You made a good point. Thanks


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## McClary’s Electrical

MDShunk said:


> What I'm afraid of is that my opinion (and yours) does not match up with the model standard.


 

now that I've read post # 8 , I would agree with this statement:whistling2:


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## MDShunk

Wirenuting said:


> But then we think,, who needs PPE to reset a breaker?


Maybe me? I don't know. That's what I'm trying to sort out.


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## Zog

mcclary's electrical said:


> Yes, but they're still made that way. IMO, a person does not need the same level of PPE to push that reset or close the disconnect, as he would to open the enclosure.


You are incorrect, unless the equipment is arc rated per the ANSI test standard for that equipment. Huge misconception in the industry that enclosures are designed or tested to contain an arc flash.


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## Zog

Wirenuting said:


> But then we think,, who needs PPE to reset a breaker?
> You made a good point. Thanks


You do, if the arc flash label says so, regardless if the doors are open or closed. Or if you do not have a study yet, use the tables if you are within the limits of the notes.


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## Zog

MDShunk said:


> I disagree that gear is designed to contain the arc blast. Study after study has shown covers launched at a hundred miles an hour. Even the so-called arc safe switchgear doesn't contain the arc blast. They have those dotted plates on top that blow off and shoot the blast straight up.
> 
> I found somthing:
> 
> _FPN No. 1: An arc flash hazard may exist when energized electrical conductors or circuit parts are exposed or when they are within equipment in a guarded or enclosed condition, provided a person is interacting with the equipment in such a manner that could cause an electric arc. ...._
> 
> 
> When operating a disconnect, one never knows if that operation of the handle you are about to perform may cause something to break and go phase to phase.


You got it Mark, exactly right,:thumbup: The issue is that there are not, and never will be open door and closed door arc flash equations. All calculations are assuming open door. You don't know the condition or design of the enclosure, rust, missing hardware, etc.. so a closed door calculation is impossible. 

Another issue here, some testing suggests that the arc blast can be more damaging with the doors closed, when the doors are open the pressure from the arc flash dissipates quickly, like lighting gunpowder in your open palm. With all the sides enclosed the pressure has a chance to build, until something fails, which is usually the flimsy latch on the dorr you are standing in front of, releasing a large amount of energy. Like lighting gunpowder in your clenched fist, KABOOM!. 

IEEE 1584 is starting to do some research on arc blast, meaning the pressures, so far most if the studies have focused on the arc flash, the heat that is released.


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## Wirenuting

Zog said:


> You do, if the arc flash label says so, regardless if the doors are open or closed. Or if you do not have a study yet, use the tables if you are within the limits of the notes.


It took years to get the gloves reissued to us. I had to show them all the time and about dare them to discipline me over them. They finally gave in and now we have a testing program for them again. 
But that were the PPE here ends. 
Besides a hardhat, nothing is enforced. 
I kind of feel sorry for the new guys being hired. Just do it and don't worry is what they are told. 

*note* a few weeks after I hired in an electrician died in a bucket truck outside the building I was working in. They brought back a safety program just long enough to forget the mans name. 
Now were are back were we started.


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## jwjrw

Wirenuting said:


> It took years to get the gloves reissued to us. I had to show them all the time and about dare them to discipline me over them. They finally gave in and now we have a testing program for them again.
> But that were the PPE here ends.
> Besides a hardhat, nothing is enforced.
> I kind of feel sorry for the new guys being hired. Just do it and don't worry is what they are told.
> 
> *note* a few weeks after I hired in an electrician died in a bucket truck outside the building I was working in. They brought back a safety program just long enough to forget the mans name.
> Now were are back were we started.



Does osha inspect your workplaces?


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## Wirenuting

jwjrw said:


> Does osha inspect your workplaces?


LoL,, no
They came once to "interview" a few of us many years ago. I think it was to help them modify their interview protocol.
We try to conform to their standards,, 
But in the end we are not "bound" by OSHA.


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## guest

MDShunk said:


> When operating a disconnect, one never knows if that operation of the handle you are about to perform may cause something to break and go phase to phase.


Exactly. I have personally had FOUR of the old "Bulldog" switches explode on me while turning them off. In all but one case the guts' mounting hardware failed and slammed the internals against the door when I pulled the lever. The other one never knew what went wrong, it was totally destroyed. 

Even when resetting breakers in a resi panel I am now in the habit of standing off to one side and looking away during operation.


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## oldtimer

mxslick said:


> Exactly. I have personally had FOUR of the old "Bulldog" switches explode on me while turning them off. In all but one case the guts' mounting hardware failed and slammed the internals against the door when I pulled the lever. The other one never knew what went wrong, it was totally destroyed.
> 
> (Even when resetting breakers in a resi panel I am now in the habit of standing off to one side and looking away during operation).


 Good practice to get used to!

I (touch wood) have never had one blow in my face, but have had a few short out and burn.

I consider myself extremely lucky. :clover:and I'm not even irish!

I admit I have taken some foolish chances, and in hindsight, realize how dumb I was. I strongly advise caution.


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