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.

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.

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.

Steve,
Wouldn't you have to isolate the supply to the disconnect before opening it anyway?.
Ron is right though.

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.

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.

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

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.

Good points RayS.
And Welcome to ECN!.

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.

The view "yes, there are exposed live parts, so you must suit up" is what is taught in the "safety" classes.

I disagree.

With the shields in place, the 'live' parts are well recessed, and cah only be reached with a set of probes- a finger, or piece of falling debris won't make it. IMO, these points are even less exposed than the 'exposed live parts' of any receptacle. Or cord cap.

Now, writing the rule properly might be a bit difficult- but the rule book does not exist for the ease of the authors!

Now, some will say that a 'safety' rule can never be too strict. I disagree. A rule that is not realistic will not only be ignored, but will lessen your respect for all rules. I'd rather not see 'ignore the silly rule' become SOP. Better to have a better rule.

Reno, thank you!! A breath of common sense!! (But see more info below..)

Now if we can kill off those pesky AFCI's......

My new slogan: AFCI's: The airbags of the electrical industry.

Back on topic:

I too am wondering why the disconnect will be open at all times. (And is this referring to the door or the switch blades themselves being open?)

If it's the door, then yes, I feel full PPE will be required anytime anyone is in the arc flash boundary of this disconnect. Remember that if the switch blades are closed, they and any fuses and of course the load lugs are now live.

If the switch blades will be open, i.e. "off" at all times then it could be argued that no, there are no exposed live parts. Thus no real need for PPE.

Finally, 480 volts is nothing to futz around with. Is wearing full PPE a hassle? Probably. How about several days in a burn ward, months in a coma or eternity six feet under? Those are a hassle.

My take: Covered lugs or not, put on the damn PPE!!!**


**EDITED TO ADD THE FOLLOWING POINTS:


Very true Reno, and I do agree with the idea that under these conditions it would be reasonably safe to approach this disconnect without PPE. BUT, the OP points out that the door would be left open all the time, presumably even when the disconnect switch blades are closed and energized. So full PPE would be required and not considered overkill.

I had to add this information as it seemed that I was presenting conflicting views in my original post.

[This message has been edited by mxslick (edited 10-08-2006).]

MX, I am pretty sure I understand what you are trying to say.

Opening the disco, and using your meter to ensure that power is OFF is one thing.

Opening the disco, then bypassing the door interlock so as to cycle the switch and operate the equipment is an entirely different matter.

I apologize for any confusion I may have caused. When I stated in my original post that "the switch would remain open at all times". I was not referring to the enclosure being open at all times. I was attempting to elaborate that the knife switch would not be energised (switched to the ON position) while the electrician was working in the enclosure.

Sorry for any confusion I may have caused.