Class III locations usually include textile mills that process cotton, rayon, and so on, where easily ignitible fibers or combustible flyings are present in the manufacturing process. Sawmills and other woodworking plants, where sawdust, wood shavings, and combustible fibers or flyings are present, may also become hazardous. If wood flour (dust) is present, the location is a Class II, Group G location, not a Class III location.
I thought that saw dust would have fallen into Class II locations. Class I is flammable vapors and gases, Class II is dust, and Class III is Ignitable Fibers and Flyings??? Although wood dust is not exclusively mentioned in the UL classifications, would it not be considered a Class II location. Just asking the elctrical experts.
The simple presence of wood saw dust does not create a Class II hazardous location. If it did all of our circular saws and sanders would need to be dust ignition-proof.
According to Killark's 1999 National Electrical Code Review & Application Guide " To be considered a "dust" the combustible material must exist as a finely divided solid of 420 microns (0.420 mm) or less. Such a dust will pass through a No. 40 U.S. sieve."
Re: Bewildered! Designed by the Woodshop Supervisor#103753 11/08/0207:46 PM11/08/0207:46 PM
Roger, Good eye with the additional disco. Also, above the (non-xp)panel is what appears to me an explosion-proof j-box of similar classification. Either somone got a deal on surplus or stolen materials, or some contractor sold the owner a line of bull.
[This message has been edited by Redsy (edited 11-11-2002).]