Canopy Over a Building

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charlie b

charlie b

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Let me call this an "academic exercise."

Consider a small office building (one or two stories, perhaps 1500 ft2) with just some basic electrical loads (i.e., lights and receptacles). Suppose I were to install a canopy over this building, without it actually touching the building at any point. Let the canopy be a metal-framed structure. Let us not allow any electrical devices (e.g., exterior lights) to be attached to the canopy.
1. Would I need to call for any provisions for grounding the canopy, or for bonding its metal frame to the reinforcing steel of the office building it covers?
2. Would the NEC even apply to the canopy?
 
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Interesting question. If the metal canopy qualifed as a grounding electrode, per 250.52(A)(2) then is it present at each building served? Its obviously present, but not at the building. I would bond a appropiate size copper jumper from the canopy to the small office buildings grounding system, as what I see later on is installing lighting or receptacles on the canopy.
 
charlie b said:
Let me call this an "academic exercise."

Consider a small office building (one or two stories, perhaps 1500 ft2) with just some basic electrical loads (i.e., lights and receptacles). Suppose I were to install a canopy over this building, without it actually touching the building at any point. Let the canopy be a metal-framed structure. Let us not allow any electrical devices (e.g., exterior lights) to be attached to the canopy.
1. Would I need to call for any provisions for grounding the canopy, or for bonding its metal frame to the reinforcing steel of the office building it covers?
2. Would the NEC even apply to the canopy?
Click to expand...

Since it is not touching the existing structure and does not have any electricity on it, my guess is no.

However, putting what amounts to a tarp on a frame over an existing structure probably violates some part of the building code.
 
I have learned a couple things, since first posting the question.
1. The building is not for offices, but rather is manufactured housing.
2. The canopy will indeed have no electrical components attached.
3. The canopy will be of a substantial construction, not just a tarp attached to poles. So building codes will not be a concern.

I now have a couple more grounding-related questions. Consider a group of ten manufactured housing units, attached to each other two-high by five-wide. Each has its own branch panel with a main breaker. Each of the ten units is fed from an individual breaker on a nearby distribution board.
1. Am I right in concluding that if the distribution board is across a sidewalk from the units, mounted on a unistrut frame, then I need separate ground rods for the “unistrut structure” and separate ground rods for the 2x5 unit housing unit group?
2. Am I right in concluding that if the distribution board is across the sidewalk, then I would need “special permission” under 225.30(B)(1) – NEC 2008?
3. Am I right in concluding that if I mounted the distribution board on the side of one of the housing units, then I only need one set of ground rods?
4. Am I right in concluding that if there is a nearby pad-mounted skid (e.g., with water pumps serving the units) that is fed from the same distribution board, then I need separate ground rods for the “skid-mounted equipment structure”?
5. Am I right in concluding that if I have two or three separate sets of ground rods (i.e., for the distribution board on its unistrut, for the housing units, and for the skid-mounted equipment), then I need to bond them all together, since it is all fed from the same power source?
 
Does it require a ground rod at all?

If it is sitting on the ground on a metal frame isn't that adequate as a GE?

Is it not likely there is some kind of concrete foundation that would serve as a CEE?
 
This doesn't really sound like manufactured housing in the way I would understand it as per HUD, it sounds more like a modular type of construction, more like an Alaska oil well camp kind of thing, if so I would treat it as one multi-family dwelling and bond accordingly, and since it is all put together as one unit, it only needs one grounding electrode system.

As far as the water pumps, go I think only an EGC is warranted, calling a water pump a structure is kind of reaching, and I have never been required to install electrodes at one, beside wouldn't the pump be fed with a branch circuit?
 
Calling it an Alaska oil well camp is not too far from reality. But it is not a "dwelling unit," as there are no provisions for cooking. I describe it as a "manufactured home" because it meets the size requirements of the definition of that phrase, as given in 550.2.

I am thinking in terms of 250.32 (2008 NEC). If I pour a concrete pad a short distance from the housing units, and place on the pad a manufactured skid that has potable water pumps or gray/black water pumps, would not that be a separate structure? Would not 250.32 come into play?
 
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