NEC_Table 110.26
- Thread starter GLM123
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Carultch
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It means completely clear space in front of the equipment. So it is from the cover itself of the equipment, that contains the live parts.
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- Lockport, IL
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- Semi-Retired Electrical Engineer
Perhaps it is not as simple as that. Tell me about the "rack." I see "telecom" in your profile, so I infer you are talking about a rack that holds telecom equipment. But are you asking about the possibility that one of the rack-mounted components might stick out past the frame members that comprise the rack? If so, then my answer would start by inviting attention to the sentence that is immediately above the table. The measurement starts at the exposed live parts or at the front edge of the enclosure. But I wonder if the NEC applies to this situation. Doesn't BISCI or other organizations have its own requirements for clearance around telecom equipment?
You are correct it is a telecom rack I'm speaking of. One that would house IT equipment i.e. routers, switches, servers etc... So yes, if any of those components stick out past the rack frame is that where the 3 ft. clearance requirement is in effect? From the code that is what I've usually interpreted but I have often been asked where it applies. From the rack or the longest piece of live equipment both front and rear? Usually asked by facilities and/or architects that hate to give up space for IT, so of course they want the answer to be from the rack. At the planning stages it is difficult to answer because you may not know what the longest piece of equipment will be.
In this case BICSI defers to the NEC.
Thanks for your input
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- Lockport, IL
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- Semi-Retired Electrical Engineer
The NEC says that the clearance starts at the location of the exposed live parts, or at the front fact of the enclosure (if the exposed live parts are enclosed, as they would be inside a power panel). So tell us, what parts are live and exposed? I suspect that for any component that you mount in this rack, all energized parts would be located internal to the case. From the projects that I designed alongside an IT designer, I recall that each component receives its power by plugging into a standard receptacle outlet that is mounted on the rack. I can't think of any part of the rack itself or any thing that you would mount on the rack would have exposed live parts. In that were true, then perhaps the working clearance requirements in 110.26 might not apply at all. But the real bottom line is this: is there any maintenance or repair activity that would be done with the equipment energized, and for which the activity requires something to be opened such that a person's hand might touch a live metal part?
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- Lockport, IL
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- Semi-Retired Electrical Engineer
There is a bit of a tricky aspect to this question. Suppose for the sake of discussion that a person might have to do live work on some component on the rack or on the rack itself. The NEC would require working clearance, starting at the face of the rack. But the NEC would also require that nothing be located in the box that starts at the front face, is 30 inches wide, 36 inches deep, and 78 inches high. So if you have a component sticking out the front face of the rack, that component could be considered to infringe on the required working clearance.
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