450.13 "Hollow Space"

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charlie b

charlie b

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I envision this phrase to mean the area between the structural ceiling and a suspended ceiling, as you might have in an office or retail building. A colleague is designing a project in a waterfront area that will have kiosks for small coffee shops and other vendors. The utility will only provide 480 volts, so the kiosks will need step down transformers. The ceilings will be very high and will include large glass windows in the upper regions. There will be some manner of suspended ceiling above the kiosks, but a person will be able to climb a ladder and walk along catwalks that are above that suspended ceiling, so as to be able to clean the windows. I do not see this as being "hollow," in the context of 450.13. So the 50 KVA limit would not apply.

Anyone care to comment?
 
It occurs to me that I was standing on a catwalk above a hard lid ceiling just last week. There were mechanical and electrical components in the area, along with a host of pipes and conduits. As I "strolled" along the catwalk, there was space around me and above me. I see this as being an area similar to my original question. There were 225 KVA transformers in the area. I would not have called this a "hollow space," so the 50 KVA limit would not apply here either.
 
I would take 450.13.B to mean a space more like a nook in a wall, a cavity of some sort because of the accompanying language. (i.e. ventilation requirements, separation requirements) Sounds from your description that the area is more room like.
 
I'd agree also. IMO, "hollow" spaces are not normally accessed, and access would normally required removing a ceiling tile or something similar.

Since there are catwalks and permanent ladders, I would consider your application an "Open Installation" per paragraph A.
 
Is a room a hollow space, until you bring something into it?

Put a transformer in a room all by itself you may be in violation here, put a panelboard from the secondary in the same room and now it is at very least an "electrical room" and not just some hollow space?

:huh:
 
kwired said:
Is a room a hollow space, until you bring something into it?

Put a transformer in a room all by itself you may be in violation here, put a panelboard from the secondary in the same room and now it is at very least an "electrical room" and not just some hollow space?

:huh:
Click to expand...

IMO, it's all about access. A room is never a hollow space if it has a doorway to enter the room.

Take the same room, remove the doorway so that one must access it by a less convenient method, and you have a hollow space. (Say for example you had to access the room by climbing up through a ceiling tile, over a wall, and down through another tile. Then its a hollow space.)
 
steve66 said:
IMO, it's all about access. A room is never a hollow space if it has a doorway to enter the room.

Take the same room, remove the doorway so that one must access it by a less convenient method, and you have a hollow space. (Say for example you had to access the room by climbing up through a ceiling tile, over a wall, and down through another tile. Then its a hollow space.)
Click to expand...

So can one put say a 150 kVA transformer in a attic or crawlspace that needs no ladder or other special equipment to gain access to the space, yet the "doorway" may still be a small access panel of some sort instead of a 6-7 foot high hinged door? Is there a minimum dimension or type for the "door" I guess is what I am asking here?

Large open construction type stores, don't have such hollow space in ceiling area, but put a larger transformer up high (may not be real common for other reasons, but would be allowed) and someday down the road decide to put in a drop ceiling and now you must also lower the transformer I guess.
 
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