Sharing Space Over Panels: OK If Safety Issues Addressed
Don't read too much into the new 6-ft dedicated space rule over panelboards, switchboards, and motor control centers.
Does the new 6 ft clearance rule above panelboards, switchboards, motor control centers, etc. prohibit other systems from invading the space directly above this equipment? The popular answer ("It's our space, and no one else's") is also the wrong answer.
The EC&M panel's response. We think you can have other systems in this zone, if you address the related safety issues. Since this topic has become so heavily debated in the industry, we feel it's necessary to put it in some historical perspective. Let's start with the 1999 NEC rule, in Sec. 110-26(f), a piece at a time:
(f) Dedicated Equipment Space. Equipment within the scope of Article 384, and motor control centers, shall be located in dedicated spaces and protected from damage as covered in (1) and (2).
Exception: Control equipment that by its very nature or because of other rules of the Code must be adjacent to or within sight of its operating machinery shall be permitted in those locations.
(1) Indoor. For indoor installations, the dedicated space shall comply with the following.
(a) Dedicated Electrical Space. The space equal to the width and depth of the equipment and extending from the floor to a height of 6 ft (1.83 m) above the equipment or to the structural ceiling, whichever is lower, shall be dedicated to the electrical installation. No piping, ducts, or equipment foreign to the electrical installation shall be located in this zone.
This sets a presumption of 6 ft of dedicated space. If you stopped here, you'd correctly assume no nonelectrical equipment could go above (or below) this equipment. For a little more perspective, let's jump over the exception following and go to (b) on foreign systems.
(b) Foreign Systems. The space equal to the width and depth of the equipment shall be kept clear of foreign systems unless protection is provided to avoid damage from condensation, leaks, or breaks in such foreign systems. This zone shall extend from the top of the electrical equipment to the structural ceiling.
This corrects a problem in prior versions of the rule, formerly located in the now deleted Sec. 384-4, which didn't enforce the protection rule to the structural ceiling if it were more than 25 ft above the floor. Obviously, the contents of a leaking pipe won't evaporate in that distance as they fall toward the switchboard. Regardless of height, now you need to be sure a leaking pipe, trap cleanout, etc. won't endanger the equipment. Now we can return to the exception to (a):
Exception: Equipment that is isolated from the foreign equipment by height or physical enclosures or covers that will afford adequate mechanical protection from vehicular traffic or accidental contact by unauthorized personnel or that complies with (b), shall be permitted in areas that do not have the dedicated space described in this rule.
If you want to really understand this rule, you should realize how this exception came to be worded as it is today. When the dedicated space rule first appeared in the NEC (1981 edition), it carried with it essentially the same exception, with one crucial difference: It only applied to "Equipment located throughout industrial plants..." That allowance followed this rule intact through the years; until this cycle.
When CMP 9 took up this issue during the 1999 NEC comment period, the panel decided to work from two comments on its earlier work that didn't mention any dimensions. One comment asked for a dedicated 6-ft zone while retaining the 1996 exception intact. One suggested reorganizing the 1996 NEC requirements to tease out the foreign systems rule, but made no other substantive change.
One panel member moved to combine the two comments, adding the dedicated 6-ft clearance to the reorganization proposal. That was the main motion. This editor (a member of CMP 9) moved to amend the motion by stripping the four words "located throughout industrial plants" from the exception.
CMP 9 members discussed the merits of whether there was any reason other than politics to prevent occupancies other than industrials from using an allowance that had been in place for six code cycles without reported incident. Not one member of the panel could think of any safety reason why that should not be so. Why should only industrial occupancies, some with tremendous process fluid exposures, be allowed to use drip shields? Why indeed, when a single-family home had to rack a panel out from the wall just because the plumber got there first and ran a sewer pipe past the panel location? Even underneath the panel, with no exceptions allowed? Even with Type NM cable as the wiring method, which hardly requires anything approaching 6 ft to entrain into a panel?
Not one member of CMP 9 could think of a safety reason to vote no on the amendment, and it carried unanimously, with one abstaining vote. Subsequently, another panel member pointed out with the foreign system rule (b) separated from the principal rule (a), the exception had to be further amended to reference the following paragraph. If you have the dedicated space, use it. If you don't, use the appropriate equipment or provide adequate barriers.
Is there a safety issue? The back and sides of electrical equipment comprise five sides of a rectangular solid. You can exit any one of those sides safely, although the more options you have, the better the overall design. So, what about the proverbial air duct running 2 in. above a panel? Under the exception, could you get away with a drip shield to protect against condensation, and locate a panel at that point? Absolutely; you don't "have the dedicated space described in this rule" and thereby qualify for the exception.
Are we all going to die because you can't exit vertically in that case? We don't think so. What about a column-width panel in the webbing of a vertical I column with two whole sides of the panel, and the back, completely obstructed! Some EC&M panel members had to defend enforcement of the prior version of this rule in front of a disinterested authority. The result? With no safety issue at hand, enforcement of the rule lost every time.
Medium voltage. It gets even better when you look at medium-voltage installations. Former Sec. 710-9, now relocated as Sec. 110-34(f), allows the same thing as now allowed for 600V and below:
(f) Protection of Service Equipment, Metal-Enclosed Power Switchgear, and Industrial Control Assemblies. Pipes or ducts foreign to the electrical installation that require periodic maintenance or whose malfunction would endanger the operation of the electrical system shall not be located in the vicinity of the service equipment, metal-enclosed power switchgear, or industrial control assemblies. Protection shall be provided where necessary to avoid damage from condensation leaks and breaks in such foreign systems. Piping and other facilities shall not be considered foreign if provided for fire protection of the electrical installation.
This section actually has a longer pedigree than the rule for 600V and below, having first entered the 1975 NEC. Here again, the rule squarely addresses safety, allowing for the arrangement of field protection if necessary. It was amusing to review a recent analysis of Sec. 110-26(f) in a competing publication in this context. The drawing in the other analysis clearly shows a voltage rating of 13.8kV, which means the discussion should have centered on the medium-voltage allowances continuing without incident for 25 years.
Communication is key. Let's try to remember we don't own the real estate. In the end, the owners have to live with whatever decisions they make about sacrificing future workability on the altar of low initial costs. There are always ways, often very expensive, for you to get wiring extensions out of overly cramped electrical rooms, and done safely. We know, because we've all carried tools and had to do it.
It's our job, though, to carry this burden of communicating with other professionals. Don't ask the Code to do that for you. If you succeed, you'll lose in the end, because you'll destroy the moral authority of a Code squarely based on minimum safety, and not the convenience of its users. Remember, other interests want to take the NEC away from our industry. Ultimately, public authorities outside our industry will make that decision. They never heard of Ohm's Law, but they'll spotsomething that looks and smells like an economic benefit to a special interest masquerading as a safety rule from far off. Now they'll have to look somewhere else.
EDITOR'S NOTE: These answers are given by our panel of experts. This author chairs the panel. Other panel members include: Bill Summers, James Stallcup, Dan Leaf, and Joe Ross
The opinion expressed is that of the panel. If a panelist disagrees with the majority opinion, his explanation is printed following the answer. Although authoritative, the answers printed here are not, and cannot be relied on as formal interpretations of the NEC.