Class 3 div 1 or not.

[Santiago]

I am doing an electrical design for a wood truss manufacturing building. The equipment in this building has a couple enclosed saws, one Metra-cut saw, and a few manual skill saws.
I have been told that the amount of fibers produced are far less than that of lets say a cabinet wood working plant.

Would this building still be considered a Class 3 division 1 area?

 

[rbalex]

Re: Class 3 div 1 or not.

This has been discussed in several threads:

http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=22;t=000021

http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=22;t=000025#000004

http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=get_topic;f=22;t=000053

My personal opinion is that, unless there is a significant continuous amount of air-born ?wood flour? present (not likely in most modern facilities), the location does not need to be classified.

 

[john m. caloggero]

Re: Class 3 div 1 or not.

RBAlex: I agree with you 100 percent.
If a dust layer greater than 1/8 in. thick is present under normal conditions, the area should be classified as Division 1. Dust is defined as:Any finely divided solid material 420 microns or less in diameter (i.e., material passing through a U.S. No. 40 Standard Sieve). Most of the material in the wood-working facility would be of a much larger size.
Good house keeping is required to keep debris from covering heat generating electrical equipment and acting as thermal insulation preventing dissipation of heat.

 

[john m. caloggero]

Re: Class 3 div 1 or not.

Extracted from NFPA 499.
Thickness of Dust Layer

Classification
Greater than 1/8 in. (3 mm)ivision 1

Less than 1/8 in. (3 mm), but surface color not discernible: Division 2

Surface color discernible under the dust layer:
Unclassified