I need clarification of art 511

[detroitelectrician]

I am doing a 2 bay oil change and I got a red tag for plugs in customer wait area at 17 inches. The AHJ said they must be above 18 everywhere. There is ventilation of the pit area only (1200 cfm )with 6 air changes per hour. I was told that all conduits thruout must be 18 inches from the floor and 18 from the ceiling. They will not work on any CNG vehicles, is he wrong for requiring all conduits 18 below ceiling?

If the ventilation makes the pit unclassified what areas are still classified?

Thanks for any help or comments

 

[wbalsam1]

See 511.3(A)(3) for help in defining these spaces/uses. I know that NFPA 30 deals with the definition of minor repair garage. If this place fits that description, then there can be no transference of flammable or gaseous liquids. If there are no fuel transfers, the pit is not a classified area if it has exhaust ventilation at not less than one cubic foot per minute per square foot of floor area....see 511.3(A)(4). I don't see how areas effectively cut off by walls, etc., such as customer waiting rooms can be considered part of the classified area.....

 

[petersonra]

I don't see how areas effectively cut off by walls, etc., such as customer waiting rooms can be considered part of the classified area.....

None of the quick lube places around here have walls between the waiting area and the work area. At least none I have been in - except WalMart. But they make you wait 3 miles away so you can't see them work on your car. I hate that and won't go to places that do that.

 

[detroitelectrician]

A door between areas

A door between areas

There is a seperate waiting room but it has a door to the oil change area.

The insp. told me because of the door the wait area is a hazardous area.
But the pit is not because of the exhaust fan.

There is no plan to work on CNG vehicles, but I was told to stay 18 inches from the ceiling with all raceways and fixtures.

I think this is going above code, what do you guys think?

 

[bobgorno]

NFPA 30A Motor Fuel Dispensing and Repair Garages (2003), Table 8.3.1 - Sales, storage and restrooms are nonclassified unless they have an opening within the extent of a Division 1 area.

Also, windshield washer fluid dispensing does not create a classified area per 8.3.5, Exception and NEC 511.3(A)(2)

I can't imagine a business that has a sales room with a door opening to a non-ventilated pit.

 

[Pierre C Belarge]

I don't see how areas effectively cut off by walls, etc., such as customer waiting rooms can be considered part of the classified area.....

I agree with this. The places we see around here are closed off to the work area, usually with a glass window so you can view your car being worked on.

Do we really think that these places would permit the general population to hang out in Classified locations?

 

[831]

Is there positive pressure into the garage from the waiting room i.e. is the HVAC unit pushing air out that door when opened - I would think so. If air flow is positive into the waiting area, the AHJ has a point. If not, I'd pull out Article 500 and take him/her to lunch (probably a McD right by) and discuss/agree.

 

[mvannevel]

If the ventilation makes the pit unclassified what areas are still classified?

That will all depend on the ventillation which is provided. Just as the pit had to be provided with a minimum of 1cfm/sq. ft. to be unclassified, 511.3(B)(2) requires that the main level have that same 1cfm/sq. ft. or be classified as a Class I, Division 2 location. If the main level is Class I, Division 2, then you'd need to meet the requirements of 511.3(B)(4) to be unclassified in the waiting room. Or, possibly prove ventillation or positive pressure in the waiting area and get special permission as stated in 511.3(B)(5).

Now, as far as CNG vehicles never coming through for an oil change, that might be a tough one to prove.

All of this will be a little easier if we ever adopt the '05 Code. However, that's not going to do you any good in the meantime. Get your ducks in a row as far as the ventillation in the rest of the building and sit down with the inspector and discuss how these areas will be classified.