Valerie

Status
Not open for further replies.
elecplans

elecplans

Member
Location
Texas
Can anyone elaborate as to why the "over six feet in width" rule that was deleted in the 2005 code (110.26C2) is being put back in to the 2008 NEC? I felt this was a good move to take this wording out.
 
From Mike Holt's book:

"The requirement that equipment rated at 1200A or more had to be over 6' wide before an entrance was required at each end of the working space was removed. The argument for the change was that the size of the arc blast is directly related to the ampere rating of the equipment, not the physical width of the equipment."
 
Valerie

Trevor,

The ROP cd that I have indicates that it was accepted to put the wording back in (ROP 1-127, Log #3487). Was this changed again at a later date? I agree that the arc blast is related to the ampacity and not to the overall size of the equipment.
 
The over six food wording will be back in the 2008 code. There were many objections to my change that was in the 2005 code. I think the CMP was still upset about my comment in the 2005 ROC that resulted in the deletion of the 6' rule. That comment(1-247) read in part:
I can only assume that the panel members would be happy to walk
by the 5 ft. 8 in. 1200 amp gear while it is in a fault condition to get out of the room, but that they would be afraid to walk by the 6 ft. 1 in. 1200 amp gear under the same conditions.
Click to expand...

I still feel that the 6' rule should be deleted. The hazard is related to the energy available and not to the physical size of the equipment. Maybe the 6' rule should be based on the available fault current and not the amp rating of the equipment.
Don
 
I can only assume that the panel members would be happy to walk
by the 5 ft. 8 in. 1200 amp gear while it is in a fault condition to get out of the room, but that they would be afraid to walk by the 6 ft. 1 in. 1200 amp gear under the same conditions.
Click to expand...

nice >>>>>> :D
 
valerie

valerie

That was a good one! Having been in such a situation (several years ago), I can really relate. I appreciate the response.
 
This was Dons proposal for the 05 code and it was rejected at the proposal stage and then accepted as a comment. Perhaps the code language should be tied to the arc fault current, certainly not the width.
I appreciate all Dons work
His Proposal 5-1 woke up a lot of folks and its still making changes.
 
tom baker said:
Perhaps the code language should be tied to the arc fault current, certainly not the width.
Click to expand...
Don had a good idea here, at least from a technical perspective. The problem, of course, comes from the notion of enforcement. Any Inspector can bring a tape measure into a room, and discover whether or not the gear is over six feet wide. How can anyone tell what the available fault current is, during an inspection? Does everyone always hire an engineer to perform such calculations, and are the signed and sealed calculations always available at the job site for the Inspector to review?

More to the point, the amount of fault current available at any given point may change, over the life of the building. If you add a big motor next year, that may put you over the threshold for needing a second door. Are you going to want to have a new door included in your new motor project?

All that aside, I never understood the basis for this second entrance to the working space. When a fault takes place, if you are in front of the gear, you may have a bad day. But if you are safely off to the side when the event takes place (and I know of a very recent fault in which the operator was, in fact, safely off to the side, and therefore was not injured), you should be able to simply walk away. The fault is over (because some OCPD will have de-energized the faulted equipment), and so too is the danger. Immediately after the event, it should be safe to walk right in front of the gear, and right out of the room. What?s the point of having a second direction in which to walk away? Just asking; just confused.
 
Charlie,
I think the point is that not all faults arcing faults quickly open the OCPD. If this is service equipment, the fault may never open the OCPD on the primay of the utility transformer. The fault may also start things on fire blocking your exit path if there is only one way out.
Don
 
charlie b said:
How can anyone tell what the available fault current is, during an inspection?
Click to expand...

Charlie, this is becoming a hot topic here as of late. I had better have the calcs. ready for the AHJ. We, (myself and the AHJ) rely on guys like you to do your home work getting the best info possible from POCO.

And we really appreciate all thats involved.
 
Status
Not open for further replies.
Top