Step-down from electrical equipment platform. How big must it be?

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Dark Sparky

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In this thread:
http://forums.mikeholt.com/showthrea...ht=egress+step

Charlie mentions:
"If you were to draw lines on the floor to depict the required working clearances around all the equipment in the area, would there be space on this level that is not within the lines? In other words, can you be standing within the working space in front of any of the equipment, and walk out of the working space, and still be on the same floor level? If so, the manner of egress from that point to the outside world is not within the scope of the NEC. All the NEC cares about is that you can safely leave the designated working space."

We have a scenario where we need to put some electrical equipment (MCCs, panels) all in a row on a raised platform. Once you are away from & off of this electrical platform, the rest of the area will be a (one) step down. In the above thread, Charlie mentions that one needs to be able to "walk out of the working space." I'd like some interpretations on the code requirements for our platform's size. I am unsure if the platform needs to ONLY be the size (width and depth) of the 110.26 "Working Space", or if it needs to be this size PLUS some amount so that one can step out of the working space, and still be on the same level? Or maybe there is some other proper code-mandated size. Hopefully I am clear. If the platform needs to be larger than the Working Space, how much larger?

FYI for context, this is in an interstitial space between a walk-on ceiling and a roof. Because we have the MCC, panels & transformer, the walk-on ceiling can't support their weight. Thus we will design a platform (steel grating?) to hold the electrical equipment. Because the platform needs depth (structurally), it will create an area (working space?) around the panels, from which one will need to step down.

Thank you in advance for your time and opinions.
 
I believe your situation is very similar to the one described in the thread to which you provided a link. In the other thread, when I mentioned having space outside the working area and on the same level, I was referring to the same ?floor level,? as in ?first floor? or ?second floor.? The inspector was concerned that, in order to get out of the building following some arc flash or other event, the worker would have to get from the second floor to the first floor using a ladder. My response was that if the worker could exit the working area without having to use the ladder as the exit path, and could sit quietly on the second floor waiting for someone to come to their assistance, then the NEC does not care how that person will make it from that location to the parking lot. That is a building code issue, not an electrical code issue.

In your case, it does not sound like a person would leave the interstitial level, when leaving the working area. You said ?one will need to step down.? To me, that sound like stepping down perhaps six inches or so, the normal distance of a staircase step. So let me ask what the person would be stepping on to. If the platform is only the exact size needed for working space, then when workers take that first step down from the platform, are they stepping onto a staircase leading away from the interstitial level? Or are they walking onto some additional area on the interstitial level that is a bit lower than the working space? Or are they stepping onto a vertical ladder?
 
clarification of question

clarification of question

charlie b said:

In your case, it does not sound like a person would leave the interstitial level, when leaving the working area. You said ?one will need to step down.? To me, that sound like stepping down perhaps six inches or so, the normal distance of a staircase step. So let me ask what the person would be stepping on to. If the platform is only the exact size needed for working space, then when workers take that first step down from the platform, are they stepping onto a staircase leading away from the interstitial level? Or are they walking onto some additional area on the interstitial level that is a bit lower than the working space? Or are they stepping onto a vertical ladder?
Click to expand...

Thanks, Charlie. I can clarify - when they step off of the electrical platform, they are stepping onto the "very large" walk on ceiling.

In detail - this will be a large facility - with walk-on ceiling over most of it. So the panels I am referring to are a very small part of that walk-on ceiling/interstitial level. Once you walk out of this "electrical area" (off the platform) - there is a very large area to "get away." So we have a platform the size of the working space (or larger??) - and then one step down off the platform - and then you can walk "a long ways" on the walk-on ceiling before needing to go down stairs to the first floor.
 
Why would you need this walk away area.
If it were a room, you would only need the clearances and no walk away area.
 
why extra area?

why extra area?

Nom Deplume said:
Why would you need this walk away area.
If it were a room, you would only need the clearances and no walk away area.
Click to expand...

That, in essence, is my question.

Charlie seemed to imply in the other thread (referenced above) that space is needed so you can step out of the area. Does one need to be able to walk out of the working space on the same level? Does the step down even make a difference? In other words, if the platform was exactly the size of the required Working Space, and everything outside that Space was a step down - is that ok?

Is the Working Space itself the step-back area, or is additional space outside the Working Space needed on the same level - and if so, how much. I agree, I don't see this in the code....but what does the code say?

Thanks again all.
 
What the code says is, ?At least one entrance of sufficient area shall be provided to give access to and egress from working space about electrical equipment.? Reference 110.26(C)(1). It does not say that the first step through that entrance has to be level with the working space itself. It does not say that the first step that takes you from being within the working space to being no longer within the working space cannot be a step downward, or cannot be a step onto a ladder.

The issue at stake in the earlier thread was not the same issue that we are discussing here. That inspector was concerned that in order to make their way out of the building following an electrical arc event, the workers would have to climb down a ladder. My point was that the NEC does not care if the workers leave the building or not. If the workers can leave the working space, and sit on the floor just outside the working space, then they can wait there until help arrives. It was not my intent to say that you need additional room on the same level as the working space to allow a person to step away from the working space without stepping down.
 
summary - any disagreements?

summary - any disagreements?

Thanks again Charlie, I appreciate the delineation between the situation in earlier thread versus this one. I agree entirely.

If I can summarize -

A raised platform, exactly the size of the required Working Space for the electrical equipment on the platform (and no larger), with a one step down (on the 3 sides not holding up the electrical equipment) to the rest of the walk-on ceiling, meets NEC 2011.

Does anyone agree or disagree with that statement?
 
I agree.

But let's have some fun and complicate the situation one level further. Will you need to comply with the "large equipment" rule of 110.26(C)(2)? If so, how will you deal with it? :?
 
No "large equipment" thankfully

No "large equipment" thankfully

charlie b said:
I agree.

But let's have some fun and complicate the situation one level further. Will you need to comply with the "large equipment" rule of 110.26(C)(2)? If so, how will you deal with it? :?
Click to expand...

Anyone disagree? :)
Thankfully - NO - we have no equipment over 1200A and 6' wide (none of our equipment is over 1200A).
But feel free to debate what we'd need to do if it were!
 
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