# NEC Article 511



## nitramnaed (Mar 19, 2014)

I'm an Architect, not an engineer or an electrician so this is new to me.  But I'm working on a water treatment plant and the electrical engineer is telling me that the floor for the attached maintenance garage to the facility has to be 18 inches below the facility floor.  This is due the with a requirement that certain services, in this case electrical, have to be a minimum of 18" off the finish floor.  Our electrical service room is 110' away from the garage through 2 doors in a hall through the administrative area across a 40' atrium space, then down a 20' corridor to the door to the electrical service room.

This seems ridiculous.

I read through the requirements in the NEC and I understand the reason for this requirement if the service was in the garage area and I don't know if even then it's required because I would consider this a "Minor Repair Garage" per the code definitions.

Any help with this would be appreciated.


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## north star (Mar 19, 2014)

*= = = = **>*

Refer your elec. engineer to Article 511.3(E)(1), in the `08 NEC.

If adjacent areas are effectively "cut off" by design of walls

or partitions, or have a mechanical ventilation exchange rate of

at least 4 times per hour [ or more ],   ...then the 18" height

requirement would not apply !

Is your adjacent Water Treatment Area effectively "cut off"

from the Minor Garage Repair area ?



*<** = = = =*


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## nitramnaed (Mar 19, 2014)

There is a separation wall between the garage (S occupancy) and the facility (F2 occupancy) but there is a rated door between the two.  Would this constitute an effective wall?


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## north star (Mar 19, 2014)

*= = =*

By your design, ...are the two areas [  effectively  ] "sealed off" from each

other ?

*+ + +*


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## Gregg Harris (Mar 19, 2014)

Can you post a sketch of the room in question? If ventalation is supplied the area may not even be clasified


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## nitramnaed (Mar 19, 2014)

They're of different heights.  The only penetration between the two areas is the door and any utility lines that would pass through the wall.


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## north star (Mar 19, 2014)

*= + + =*

Mr. Harris is correct !......Either [ effectively  ] seal completely the two areas

from each other, or ventilate the Minor Repair Garage area.

Recommend that you contact the E.E. and discuss the cited NEC Article.

Which edition of the NEC is being used ?



*+ = = +*


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## nitramnaed (Mar 20, 2014)

View attachment 1029


The entrance to the garage area is on the left and plan north. The electrical room is off the atrium on the right next to the seating and down a corridor.We use the 2011 NEC
	

		
			
		

		
	

View attachment 1029


/monthly_2014_03/572953d1f0e15_03-14-14OFFICEPLAN.jpg.74d5b5ee9856c435cc48316ebde8b3c4.jpg


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## chris kennedy (Mar 20, 2014)

I concur air transfer is key. This is from the 2011 NECHB commentary.


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## nitramnaed (Mar 20, 2014)

But if it's classified as a "Minor Repair Garage"?


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## chris kennedy (Mar 20, 2014)

nitramnaed said:
			
		

> But if it's classified as a "Minor Repair Garage"?


Then not applicable, never going to have to drop a fuel tank in this facility? Who is actually classifying the area?


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## nitramnaed (Mar 20, 2014)

I was told by the city that this is used for minor repairs.  Mostly to their trucks.  On and off Snow plow blades and repair.  Mirrors knocked off truck, etc.  They do the major work under contract to an outside service, engine repairs, oil service and such.


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## Gregg Harris (Mar 20, 2014)

nitramnaed said:
			
		

> I was told by the city that this is used for minor repairs.  Mostly to their trucks.  On and off Snow plow blades and repair.  Mirrors knocked off truck, etc.  They do the major work under contract to an outside service, engine repairs, oil service and such.


With ventilation it becomes unclassified Minor Repair


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## Gregg Harris (Mar 20, 2014)

Gregg Harris said:
			
		

> With ventilation it becomes unclassified Minor Repair


Is this being built or on the drawing table or all ready built?


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## nitramnaed (Mar 20, 2014)

On the boards.  Are you saying that the 4 exchange/hour ventilation is required whether it's a Minor or Major facility?

Maybe I don't need to classify it as either because of what's actually going on in the space.


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## Gregg Harris (Mar 20, 2014)

nitramnaed said:
			
		

> On the boards.  Are you saying that the 4 exchange/hour ventilation is required whether it's a Minor or Major facility?Maybe I don't need to classify it as either because of what's actually going on in the space.


Take a look at NFPA 30A

If the (minor repair) room is attached as room segment of the structure there is no need for classification unless there is a work pit involved.  If there is a work pit and ventilation is applied at a rate of 1 CFM per square foot of pit area there is no classification.


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## north star (Mar 20, 2014)

*[ . . . . . ]*

nitramnaed,

Also, look at Article 511.3(D)(1),  `11 NEC for "unclassifying" the Minor Repair area.

*[ . . . . . ]*


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