Major Repair Garage

[steve66]

For a major repair garage without any pits or below floor areas, the ventilation required to make the area non-classified is a lot (1 cubic foot per minute per square foot of floor area). That's usually about 4 air changes per hour. That's a lot of air to heat or cool, especially in the Midwest.

But if the ventilation isn't provided, everything becomes Class 1, Division 2. The entire service area and even the offices and restrooms since there are doors into the service area. This seems impossible to deal with. I assume then that any welding or grinding, battery charging, or anything that might cause a spark would be prohibited. Even an office copy machine wouldn't be allowed to sit on the floor (its not going to be listed for a class 2 location.) How can I even provide receptacles, since a cord is almost certain to hang from the outlet down to something within the classified area.

Are there any other options besides providing the ventilation or classifying the entire building?

Is it possible to designate one area for major repair and just ventilate that area with the 1 CU/M per SF? Or maybe its possible to designate one area for anything that could produce sparks, and ventilate that area?

 

[PaulMmn]

Most garages have 'port holes' in the door and rubber hoses that slip onto the tailpipe of a car being worked on, the other end out the port hole. Keeps exhaust fumes down.

But those garage doors aren't normally sealed tight-- maybe a rubber gasket across the bottom, but otherwise not air-tight. Don't know how that will factor into the air exchange equation.

And if it's a -major- garage, with multiple bays, there's a lot more air leaking around.

 

[packersparky]

The adjacent areas can be unclassified where they are designed with positive air pressure.

(E) Modifications to Classification.
(1) Specific Areas Adjacent to Classified Locations. Areas
adjacent to classified locations in which flammable vapors are
not likely to be released, such as stock rooms, switchboard
rooms, and other similar locations, shall be unclassified where
mechanically ventilated at a rate of four or more air changes
per hour, or designed with positive air pressure, or where effectively
cut off by walls or partitions.

 

[steve66]

In this garage, the port holes will be right in the floor, and piped to a fan in the corner that exhausts the air out of the building. But it only provides a fraction of the needed air changes (maybe 1/4).

I'm aware of the ability to use positive air pressure to keep an area unclassified, but only the front offices are walled off.

The service area has several bays. Then there is also a machine area that would have metal working equipment including a welder, and other things like grinders, and such. It's not walled off, so I don't see any way to allow this without providing the ventilation.

 

[kwired]

It is class 1 division 2 for application of wiring methods you may install.

NEC doesn't cover sparks produced by welding and grinding or other similar activity that may fall into this area.

I have seen standing pilot boilers, water heaters, furnaces in such areas also, If they are not supposed to be there it is because of other codes and not NEC.

You also commonly have power cords/extension cords that end up in this zone, but the receptacle they plug into is above the classified zone.

I think they just want permanent wiring methods to be classified methods just in case there is extended exposure to combustible gases and it finds it's way into the wiring method, if that method is not per hazardous location requirements, those gases have some chance of migrating through the wiring method to other areas.

 

[steve66]

It is class 1 division 2 for application of wiring methods you may install.

NEC doesn't cover sparks produced by welding and grinding or other similar activity that may fall into this area.

I have seen standing pilot boilers, water heaters, furnaces in such areas also, If they are not supposed to be there it is because of other codes and not NEC.

You also commonly have power cords/extension cords that end up in this zone, but the receptacle they plug into is above the classified zone.

I think they just want permanent wiring methods to be classified methods just in case there is extended exposure to combustible gases and it finds it's way into the wiring method, if that method is not per hazardous location requirements, those gases have some chance of migrating through the wiring method to other areas.

Yes, we got the NFPA 30 & 30A handbook, and it mentioned something similar. So I think your are correct,. Except I think any heating appliances needs to be 12' above the floor, or 8' if listed for use in a garage.

I guess the theory is that if there is a gas spill, someone can quit welding or grinding, but you can't move a conduit or receptacle out of the way. So welding or grinding is allowed, but receptacle have to be above the 18", and conduits going through the 18" has to meet all the requirements for division 2.

But what about a free standing copier in the front office? (The office would still be Class 1 Division 2, because there are doors that open into the garage, and the office isn't raised 18" above the service floor.

Its not a permanent appliance, but it could have electrical items within 18" of the floor. Is that allowed or not? I tend to think that anything that plugs in is outside the scope of the NEC. As a designer, I can't control what someone plugs into a receptacle.

 

[steve66]

New question:

Can the ventilation required to make a garage an unclassified location be controlled with a switch? Or does it have to run the entire time the garage occupied, or even 24x7?

 

[kwired]

But what about a free standing copier in the front office? (The office would still be Class 1 Division 2, because there are doors that open into the garage, and the office isn't raised 18" above the service floor.

Its not a permanent appliance, but it could have electrical items within 18" of the floor. Is that allowed or not? I tend to think that anything that plugs in is outside the scope of the NEC. As a designer, I can't control what someone plugs into a receptacle.

Is no different than a free standing powered tool in the shop, if the office is still considered in the classified area.

Past enforcement here was office needed a 1 hour wall to consider it not classified inside the office. That said some places the door may be open all day.:huh:

If office is deemed to have classified location, then all premises wiring needed to be over 18" above floor or comply with hazardous location requirements as the general rule.