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#82877 - 12/19/02 12:05 PM Supports for EMT Conduits & Boxes  
mgwatkins  Offline
Junior Member
Joined: Dec 2002
Posts: 2
San Anselmo, CA USA
I am working as a project inspector for a large project in the San Francisco Bay Area of Califonia. The electrical contractor has supported the EMT conduit and boxes utilizing screws with plastic inserts into the drywall. In my 20+ years as an inspector, I have always required that these supports be into a framing member rather than the drywall. When asked to correct the problem, the contractor indicated that NEC Article 348-12 only requires that the EMT be "securely fastened into place", and that per NEC Article 370-23 the boxes may be "fastened to the surface upon which they are mounted unless the surface does not provide "adequate support". He feels that the drywall with plastic inserts meet these criteria. I disagree. Does anyone have an opinion on this subject, or advice on how to get the contractor to support these items from the framing members.


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#82878 - 12/19/02 12:59 PM Re: Supports for EMT Conduits & Boxes  
SvenNYC  Offline
Member
Joined: Aug 2002
Posts: 1,691
New York City
I don't trust those little plastic slugs for drywall!

They're tricky to install and eventually they wind up chewing up the hole they are stuck in to the point of falling out - no friction!! I've had that happen many times (thank god I don't live in one of those cardboard boxes anymore (gypsum board is another issue entirely, I've always preferred metal mesh & cement and plaster interior walls). [Linked Image]

They also have no gripping power, so if you use these to mount an outlet box, you'll be sure to see that box dangling from the pipe after repeated plugging and unplugging appliances from that socket.

Maybe those metal inserts - with the wings that bend back against the side of the plasterboard facing the studs would work better (I believe they're called toggle bolts) as you tighten the screw?

Although who knows how good they are for holding up conduit and boxes...definitely a step up above those plastic inserts you mention.

Just my humble opinion.


#82879 - 12/19/02 07:11 PM Re: Supports for EMT Conduits & Boxes  
stamcon  Offline
Member
Joined: Mar 2001
Posts: 329
So San Francisco CA
MG, here is a link to a manufacturer of those anchors. They come in plastic as well as metal. They have a better type, that is a combination of the metal screw-in anchor with the addition of a toggle. The web page has a "Pullout" and "Shear" chart for the anchors. http://www.itwbuildex.com/ezprod.htm


#82880 - 12/19/02 08:52 PM Re: Supports for EMT Conduits & Boxes  
ZackDitner  Offline
Member
Joined: Oct 2002
Posts: 47
Kitchener, Ontario, Canada
Just tell him that you don't believe that those plastic ancors provide adequit support, suggest the use of the metal screw in type anchor in the future.

They work very well, though expensive, you screw in the anchor and then a regular screw screws into the anchor. I've used them to secure many things, including pvc, emt, picture frames, surface mount boxes (exit lighting applications), sometimes they help in addition to a few screws in the framing members, i've used to them to secure part of a panelboard that would have otherwise been able to move 1/4" on one edge because there wasn't a framing member, although the panel would not have fallen down and was adequitely mounted, the extra security of these devices helped.

Plastic plugs are crap for drywall, they're only useful in concrete, even then, it's touch and go


#82881 - 12/19/02 10:28 PM Re: Supports for EMT Conduits & Boxes  
stamcon  Offline
Member
Joined: Mar 2001
Posts: 329
So San Francisco CA
Oops, I thought the contractor was using the plastic screw-in ones. I didn't even think about the plastic expanding anchors.


#82882 - 12/20/02 11:49 PM Re: Supports for EMT Conduits & Boxes  
harold endean  Offline
Member
Joined: Feb 2002
Posts: 2,233
Boonton, NJ
Is there specs for this job? If so then you have to enforce what the engineer spec'd out.


#82883 - 12/21/02 12:19 AM Re: Supports for EMT Conduits & Boxes  
dana1028  Offline
Member
Joined: Jan 2002
Posts: 163
San Carlos, CA
On a job I was on we had an inspector tear a box off the wall (using those plastic anchors)...he said it didn't appear very secure to him!...guess he didn't like plastic anchors.(not my work, thank you)....when the electrician started to complain he opened his briefcase showed us his very dog-eared mechanical, electrical, plumbing, and building code books and proceeded to show us about a dozen microscopic code violations in all the trades...he assured us he wasn't there to nit-pick us and wouldn't bother us with citing us and charging for a reinspection, however he was sure we agreed with his 'poor securing' position for the elect. box. !! I had to bite my tongue to stop from laughing.


#82884 - 12/21/02 02:17 AM Re: Supports for EMT Conduits & Boxes  
George  Offline
Member
Joined: Feb 2002
Posts: 375
If the anchors have a load rating in drywall, I guess you could compare the load rating to the actual loading. (Pull out is perhaps the mode of failure not gravity loads.)

If the anchors lack a load rating, fail the job if you wish.


#82885 - 12/21/02 10:02 AM Re: Supports for EMT Conduits & Boxes  
mgwatkins  Offline
Junior Member
Joined: Dec 2002
Posts: 2
San Anselmo, CA USA
Thank you for your comments. I came across a good publication in the NECA 1-2000, "Good Workmanship in Electrical Contracting" which was referenced in my specifications. The project specifications indicate that the conduit and junction boxes shall be supported in accordance with good industry practice. NECA 1-2000 indicates that the "supports shall be adequately attached to the building structure or structural member." In the Junction and pull boxes section of this publication, it states "Junction and pull boxes shall be firmly and securely fastened to or supported from the building structure or structural member." I think based upon this standard of workmanship publication, I will go back and require the contractor to properly support the conduit and junction boxes to the sturcture or structural members on this project.



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