Junction box in classified location

greenspark1

Senior Member
Location
New England
Hi,
I have a 24"x24" JB that is being installed in a class I Div 1 location. All of the conduits in/out are have EYS seals per NEC. The only thing going in the JB are terminal blocks. These are used to connect wires from inside the classified location to wires pulled in from a remote location. There are no active devices or spark/arc producing components. Does the box itself have to be rated for classified locations?

501.10(A)(3) says yes, no exceptions. But I don't see the point of a $9,000 JB if there is no way that a spark/explosion could occur inside. Looking at 501.15(A)(1), the JB doesn't contain any of the components that would require sealing (switches, CBs, fuses, relays, resistors, etc). Has anyone run into this situation before? Obviously the client doesn't want to pay for a $10k JB when it doesn't seem necessary. Any input is appreciated, thanks!
 
Move It

Move It

Move the box out of the area. Extend the conduits out of the area and put the box outside. May cost a little extra but not 10K.

The reason they require the box to be rated is if something happens in it, it's contained to the box. Splices come loose and terminals break off. I Wouldn't want to be responsable for an explosion because I wanted to save a few bucks. :happysad:
 

cripple

Senior Member
Junction box in classified location

I don't see any exceptions to the rule, because 501.15 deals with the requirements for sealing and drainage. Section 500.8(A)(3) may help if the authority having jurisdiction is will to approve the installation.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Thanks for the help! I may try to sweet talk the AHJ with 500.8 but don't give it good odds.
I wouldn't give it good odds either, especially with a knowledgable AHJ.

Don't kid yourself that there is no way an arc could occur either. Terminals can (and do on occasion) vibrate free. This is one of the fundamental philosophical operating differences in Class I, between Division 1 and 2 protection. Division 2 basically concerns itself with "normal" ignition sources, Division 1 considers both "normal" and "abnormal" sources as well. Short circuits can occur in any part of the system, so every enclosure is required to be explosionproof.
 

rbalex

Moderator
Staff member
Location
Mission Viejo, CA
Occupation
Professional Electrical Engineer
Unless the raceways are 2" or larger you won't need seals for them. [501.10(A)(1)(2)]

EDIT ADD: The above only applies to the enclosure itself. Some of them may be required boundary seals.
 
Last edited:

R Williamson

New member
Location
Houston, Texas
R Williamson

R Williamson

When you go into a Class I Div. 1 Group environment all the wiring gets expensive. I have gotten better prices from Adalet on those cast enclosures.

Look into the P+H Bebco Y purge option for a Class 1 Div. 1 application with a sheet metal box. Most the gulf coast refineries use a purge for both the hazardous area plus keeping the salt air away from the copper.

I have been tempted to just fill the enclosure with transformer oil if they would let me get away with it.
 
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