Class II Division 1 or Division 2 - ?

[vickycarroll]

We have a customer in need of some advice and I thought maybe someone could answer or point me to the proper direction for some answers.


The situation is regarding how to classify a Truss Plant who cuts lumber on a saw which is used to build home trusses. Who ultimately decides whether the building can be classified Class II Division 1 or Division 2. Our customer would like to know who to consult with to see why they would not be considered a Class II Division 2.



Though we are the provider of equipment necessary for these truss plants, this is the first time one of our customers has mentioned this type of rating. From our perspective, all new truss plants have never encountered this classification so I have no feedback to offer this particular customer. I have read article 500 but I do not know who to put this customer in contact with that could be more helpful in distinguishing whether their application inside the building can be classified differently by they way they ventilate. Do you have any contacts or knowledge in this particular type of industry?

 

[rbalex]

Re: Class II Division 1 or Division 2 - ?

First, have you been routinely furnishing Division 2 equipment?

 

[vickycarroll]

Re: Class II Division 1 or Division 2 - ?

No, none of the plants that we have shipped equipment have been restricted. Our equipment is not designed for hazardous locations. We could make some changes if required for division
2, but are completely unable to satisfy the division 1 without a redesign (which will not happen)
Our customer is not familiar enough with the electrical code that they did not understand what limitations the inspector was going to be creating for them. They need someone who could help them and their inspector determine if their plant situation is truely a Class II Division 1 when other plants in nearby locations have not been restricted at all.

 

[rbalex]

Re: Class II Division 1 or Division 2 - ?

OK that helps.

The appropriate standard for classifying Class II locations is NFPA 499. That Standard define "Combustible Dusts" as:

Any finely divided solid material 420 microns or less in diameter (i.e., material passing through a U.S. No. 40 Standard Sieve) that presents a fire or explosion hazard when dispersed.

Simple sawdust won?t create that. It usually takes a fine sanding process that creates ?wood flour.? Even then it takes a dispersion mode that creates a ?dust cloud.?

If the facilities use simple good housekeeping practices Electrical Area Classification is not necessary. Your ?experience? with similar facilities is a key element. From NFPA 499 Section 3.4.8

When classifying large buildings, careful evaluation of prior experience with the same or similar installations should be made. Where experience indicates that a particular design concept is sound, continue to follow it. Sound engineering judgment and good housekeeping should be used to minimize the extent of hazardous areas.

The inspector?s recommendation is typical of the inexperienced. They over-classify, ?just to be safe.? Electrical Area Classification should never be done ?the first time? (and often even the second or third) except under the supervision of an experienced, qualified person.

 

[tony_psuee]

Re: Class II Division 1 or Division 2 - ?

Within out manufacturing plants when an issue arises about classifying an area, or changing the classification it is deferred to our insurance underwriter, who happens to be Factory Mutual(FM), to make the determination. I would suggest having the building owner involve their insurance carrier to work with the inspector on determining the proper classification for the plant.

Tony

 

[rbalex]

Re: Class II Division 1 or Division 2 - ?

Tony's recommendation is also very sound.

 

[vickycarroll]

Re: Class II Division 1 or Division 2 - ?

Thank you very much. I have passed this info on to our customer. This gives him a starting point and I hope that he is able to work this out. I am not aware of how much equipment they have ordered or received yet for this new plant as they are still in the permit process.