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#100894 - 01/18/07 08:16 PM Can conduit sealing fitting be located inside a box?  
Rich Thomas  Offline
Member
Joined: Mar 2005
Posts: 48
Seattle, Washington, USA
The situation is this:

Fifteen 1-1/4" conduits entering horizontally into a Class I Div 2 Group C,D classified area. These conduits are entering halfway up a 20-foot wall.

Are there any NEC issues preventing the conduits entering the rear of a wall mounted NEMA 12 wireway or enclosure, with the sealing fittings located on the end of the conduit stub inside the enclosure?

Sufficient space would be provided around each sealing fitting for filling with sealing compound.

Conduits inside the C1D2 area that serve equipment in the classified area would enter on the top/sides/bottom of this wireway/enclosure.

If no NEC issues, are there any other drawbacks to this arrangement?


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#100895 - 01/19/07 10:33 AM Re: Can conduit sealing fitting be located inside a box?  
earlydean  Offline
Member
Joined: Dec 2003
Posts: 751
Griswold, CT, USA
Seems a little odd to me. I do not think it does meet the requirements for Class I, Div 2. Sealoffs are required to be PRIOR to entering any enclosure. 501.15(B)

How are these conduits sealed at the entry into the box, to the box? In other words how are these conduits attached to the enclosure? But yet, they extend into the box? running thread? coupling? Myers hub? welded hub?


Earl

#100896 - 01/19/07 02:47 PM Re: Can conduit sealing fitting be located inside a box?  
Rich Thomas  Offline
Member
Joined: Mar 2005
Posts: 48
Seattle, Washington, USA
The plan is to bring buried conduits horizontally into the side of a vault.

The sealing fittings would be installed on the conduit stubs at the inside of the vault wall. No wires or sealing compound would be installed yet.

Holes would be cut into the back of a NEMA 12 box. The box would then be mounted to the wall with the conduit and open sealing fittings entering the box through the back of the box.

Many conduits inside the vault from equipment would be installed on the walls and enter the box from the sides/top/bottom.

Wiring would then be installed and the compound poured into the sealing fittings.

This method provides a simple way of transitioning from the conduit system inside the vault to the buried ductbank. I think the appearance would be clean and hide the sealed conduit stubs, which otherwise would stick out of the wall about 12-15 inches once the sealing fittings and pulling elbows were installed.

NEC 501.10(b)(4) allows gasketed general purpose enclosures for wiring where no arcing devices are installed.


#100897 - 01/21/07 11:21 AM Re: Can conduit sealing fitting be located inside a box?  
earlydean  Offline
Member
Joined: Dec 2003
Posts: 751
Griswold, CT, USA
What seals the box to the entering UG conduits? Looks like the back of your NEMA 12 box is open, no gasket there.

If you have 10 feet vertically both ways to play with, why can't you install horizontal seal-offs, close nipple to a LB, and close nipple into the top of your box? The box might have to be 12" deep, or you could mount a less deep box on strut.


Earl

#100898 - 01/22/07 12:55 AM Re: Can conduit sealing fitting be located inside a box?  
Rich Thomas  Offline
Member
Joined: Mar 2005
Posts: 48
Seattle, Washington, USA
I was planning to calk the joint between box and wall. The box is not required to be explosion proof by NEC 501.10(B)(4). It only needs to be gasketed.

Earlydean, I agree with you that this arrangement is odd. The more I think about my idea, the cornier it sounds.

I've redesigned using an approch similar to what you suggested. Each conduit stub enters the C1D2 area horizontally. A sealing fitting will be mounted on the horizontal stub, then a short nipple, then a 90-degree pulling elbow, then a short length of conduit into the top of a sheet metal pull box. All conduit in the vault can then be routed to the pull box for transition into the buried ductbank. I think this arrangement is much better. What do you think?


#100899 - 01/22/07 01:27 PM Re: Can conduit sealing fitting be located inside a box?  
earlydean  Offline
Member
Joined: Dec 2003
Posts: 751
Griswold, CT, USA
sounds much cleaner. Have fun.


Earl


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