commercial garages

[harley1959]

I have a situation where a particular location has been determined to operate as a 'commercial garage'. Within this 'commercial garage is a 'anechoic test chamber' which will be used for testing automobiles. The automobiles will be 'running' periodically during these sound tests within the chamber. The chamber is properly exhausted and vented. There are 25 air changes per hour within this chamber. Outside the chamber is a work area for the automobiles. The work area is deemed the 'commercial garage' since there will be service on these vehicles. There is 6 air changes per hour in the garage area. Problem: When fire alarm system is activated, the air handling system shuts down. I am being asked to provide interlock devices to shut down test equipment within the chamber and commercial garage areas when the fire alarm system is activated due to the fact that when the alarm is active, the air changes per hour in both the test chamber and garage area are not valid, due to their shut down, causing non hazardous type equipment, such as lighting installed 18" of the ceiling, to be required class 1, div 2 type lighting fixtures. Should electrical wiring installed within properly vented classified locations be maintained by interlock methods to shut down electrical equipment during fire alarm activation?
sorry for the winded question.

 

[lowryder88h]

Harley1959, I'm a bit confused on what your asking, my initial thaughts would be use a panel w/shunt trip main breaker interlocked w/ fire alarm. The panel would only feed those branch circuits needing to be tripped by the alarm. Hope this is what your looking for.

 

[rbalex]

As noted in the Section 511.1 FPN, a large amount of the Articles material is extracted from NFPA 30A. Sadly, what weren?t extracted were definitions of ?major? and ?minor repair garages.? See Section 511.3(A)(7) and its FPN. What you have described, sounds like a ?minor repair? operation.

I suspect you have (appropriately) classified the ?commercial garage? area as Unclassified and based that on the ventilation system. Unlike Purged and Pressurized protection schemes, the Standards don?t really specify response requirements for system failure or loss of simple ventilation schemes.

Shutting down the ventilation system is an appropriate response for the fire detection system. Of course, once a fire is already in progress, electrical area classification is usually moot.

I don?t know the full scope of the facility?s operations; but if I did, I probably wouldn?t do anything to the wiring system or lighting that you haven?t already done.

 

[harley1959]

Sorry for the confusion, it's a state I am in about 80% of the time. I reckon what I am asking is I think I should interlock the ventilation units with the electrical installations within class 1, div 2 locations. This would maintain the declassification maintained by the proper ventilation. Therefore, when the ventilation units are off, there is no possibility that class 1, div 2 locations will be operative.
By the way, this is a little more than a 'commercial garage'. It's more a testing labratory/garage area for automobiles. (Not a dyno test lab).
Hope that helps in my explanation.

 

[rbalex]

As I said, I don’t fully know your facility. I usually put that or a similar disclaimer in many of my responses because knowledge of the process/operations is essential to proper electrical area classification.

This is how NFPA 30A defines them:

Major Repair Garage. A building or portions of a building where major repairs, such as engine overhauls, painting, body and fender work, and repairs that require draining of the motor vehicle fuel tank are performed on motor vehicles, including associated floor space used for offices, parking, or showrooms. [NFPA 30A-2003, 3.3.12.1]
Minor Repair Garage. A building or portions of a building used for lubrication, inspection, and minor automotive maintenance work, such as engine tune-ups, replacement of parts, fluid changes (e.g., oil, antifreeze, transmission fluid, brake fluid, air conditioning refrigerants, etc.), brake system repairs, tire rotation, and similar routine maintenance work, including associated floor space used for offices, parking, or showrooms. [NFPA 30A-2003, 3.3.12.2]

The distinction is important because it establishes whether ventilation alone is sufficient to treat some locations as unclassified or not. Read all of Section 511.3 carefully.

It is also important to recognize that if the ventilation system is routinely shut down, rather than as an incidental response to the actuation of the fire protection system, it CANNOT be used as the basis for an unclassified location under Section 511.3(A) at any time. Conversely, if the ventilation is shut down only under extraordinary conditions, then it has no effect on the electrical area classification when those extraordinary conditions exist.

 

[harley1959]

Thank you for you responses. They have been helpful