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#151164 - 07/27/06 08:58 AM Exposed live parts or not
MKD Steve Offline
Junior Member

Registered: 07/11/06
Posts: 6
Loc: Chicago, IL, USA
A question arose today and I am turning to you for an answer. If you turn off a 480V disconnect switch and open the door. Everyone understands that the top of the switch is still energized. However, if the switch is designed with an arc shield covering the lugs. Are they still considered to be exposed live parts?

The reason I'm asking is this would decide if our electricians have to wear full arc protection gear or not? Which is a hassle!

To elaborate on my scenario, The switch will remain open at all times. The only live parts are covered and protected by the plastic cover that is part of the disconnecting means. I've searched the NFPA 70E handbook but they do not cover this situation. I have to present my findings to the safety committee so any references you could supply would be helpful!

Thanks in advance for your responses.

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Arc Flash PPE Clothing, LOTO & Insulated Tools
#151165 - 07/27/06 01:35 PM Re: Exposed live parts or not
Ron Offline
Member

Registered: 03/13/02
Posts: 577
Loc: White Plains, NY
110.8(A) printed below, indicates "while they are working on or near exposed electric conductors or circuit parts that are or can become energized". The insulating plastic sheet covering the line side of the disconnect is not rated to withstand an arc fault, and the proper PPE should be worn when working on or near the switch, in the event that an arc occurs on the line side. JMHO
110.8 Working On or Near Electrical Conductors or Circuit Parts.
(A) General. Safety-related work practices shall be used to safeguard employees from injury while they are working on or near exposed electric conductors or circuit parts that are or can become energized. The specific safety-related work practice shall be consistent with the nature and extent of the associated electric hazards.

(1) Live Parts—Safe Work Condition. Live parts to which an employee might be exposed shall be put into an electrically safe work condition before an employee works on or near them, unless work on energized components can be justified according to 130.1.
_________________________
Ron

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#151166 - 07/28/06 04:10 AM Re: Exposed live parts or not
Zog Offline
Member

Registered: 09/13/05
Posts: 116
Loc: Charlotte, NC
I agree with Ron. I had a customer with this exact same problem and I asked the 70E commitee chair about this exact senario and he basically said what Ron posted. I know thats not the answer you wanted to hear but thats what it is.
_________________________
MV/HV Testing Specialist, "BKRMAN"

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#151167 - 07/31/06 12:26 AM Re: Exposed live parts or not
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Steve,
Wouldn't you have to isolate the supply to the disconnect before opening it anyway?.
Ron is right though.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#151168 - 07/31/06 05:55 AM Re: Exposed live parts or not
MKD Steve Offline
Junior Member

Registered: 07/11/06
Posts: 6
Loc: Chicago, IL, USA
Thank you for your responses. It looks like there will be a few sweaty guys here from now on.

Trumpy, once you pull down the handle on a disconnect enclosure you can open the door. In the past it was considered safe as long as sparkey used common sense and stayed away from the top of the lugs. Those days are gone forever.

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#151169 - 08/28/06 09:28 AM Re: Exposed live parts or not
BKey Offline
Member

Registered: 12/07/05
Posts: 10
Loc: Kissimmee, Florida
FPL just had an accident where a 20 year old had turned off and Locked out the main, opened the panel, removed the screws from a buss to replace it, dropped a screw and BOOM.

He now has 3rd degree burns on his face and chest.

ANY live equipment is live unless the power source is also LOTO.
_________________________
Bryan L. Key
Safety Inspector/Trainer
Terry's Electric Inc.
An Xcelecom Company
600 N. Thacker Ave., Suite A
Kissimmee, Florida 34741

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#151170 - 08/30/06 02:26 PM Re: Exposed live parts or not
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
Wear the PPE!

Many EXO type Disconnect Switches may be opened, even if the Switch is still closed.

This is done via an auxiliary overiding cam/latch, which if turned or activated, allows the front cover to be opened while the Switch remains closed.

The purpose is to perform tests and/or view fuse data, without disturbing the load.
It is definitely for use by qualified personnel ONLY!!!

Just wanted to include this little 2¢

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#151171 - 09/20/06 05:47 AM Re: Exposed live parts or not
RayS Offline
Junior Member

Registered: 09/19/06
Posts: 2
Loc: Cincinnati, Ohio
I'll offer a contrarian opinion.

I think if there is no feasible danger of contacting the energized live parts on top (i.e. not pulling new wire into switch) the line shield should serve as an effective barrier to contact. That is it's function. It does not have to be made to resist blast, as it prevents blast from occuring by prevention. At some point, some allowance must be made for practicality; there is a point where safety is not increased significantly but added work goes thru the roof.

Let me hasten to add that if it is not a big problem to de-energize switch first, I'd do it, and ya still gotta make sure the load side is actually dead.

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#151172 - 09/20/06 09:26 AM Re: Exposed live parts or not
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Good points RayS.
And Welcome to ECN!.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#151173 - 10/07/06 09:19 PM Re: Exposed live parts or not
tajoch Offline
Member

Registered: 02/09/01
Posts: 53
Loc: Quinlan texas, usa
To elaborate on my scenario, The switch will remain open at all times. The only live parts are covered and protected by the plastic cover that is part of the disconnecting means. I've searched the NFPA 70E handbook but they do not cover this situation. I have to present my findings to the safety committee so any references you could supply would be helpful!

Ok, I'll bite, why would the covers "Have" to remain open at all times?
I open dis-connects all the time, for trouble shooting, to read fuzes, to replace fuzes, to trace circuits...etc.
But I only have the cover open while I am in front of it. or if I have a ckt tracer conected. or an clamp-on ammeter connected.

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