Conduit attachment

[DSAsteve]

The Elec drawings specify to reference SMACNA for Seismic and Attachment.
SMACNA guidelines mention attachment at 'change of direction' ie a 90* bend or sweep.

Q) is this required on all 3/4" and 1" EMT sweeps through out the project?
Q) And, would this be a "typical" installation for small conduit?

Code standard is 2001 CBC. (Calif)

Thanks,
Steve

I will post this in the SE forum also.

Inspector Steve
DSA, OSHPD, Inspector
So. California.

 

[EEJaime]

SMACNA standards were developed as a mechanical restraint system more for piping and ductwork, but for years we used them as a point of reference as they were accepted by OSHPD and DSA. If you are an inspector for both agencies we would hope you could provide us this answer. SMACNA was referenced from the electrical side mainly in reference to siesmic restraints.

It is a scary proposition to be getting this question from an OSHPD or DSA inspector, but being as it is specifically an electrical item, here goes.

CEC requires EMT conduit to be supported a minimum of every 10' and within 3' of every termination point, (every junction or outlet box, panel, LB fitting, etc....). CEC also accepts as supports, any structural component such as the studs and top plates in your picture. So as long as the conduit is supported, either by the top plate or stud or clamp or fitting within 3' of any boxes, etc..., and every 10'. It is fine. If these two conduits in the picture continue down to a box below the picture and terminate, there needs to be a clamp within 3' of the box. and there needs to be a support within 10 of where they 90 out of the top plate.

Hope that helps.

Good day,
EEJaime

 

[DSAsteve]

EEJamie,
Thank you for your reply. DSA & OSHPD yes. Electrician---no. It's my weakest discipline.
The contractor is weak also.
I did send this on to the SE, 5 days ago, and haven't received an answer as of yet. I was informed yesterday by the AOR that the SE has been out of town, (the AOR was copied my email to the SE). Anyway, the AOR agrees that the conduit needs to be anchored at each end of the sweep, (aprox 12" between straps, at over 100 locations).

However, the condition still exists. Other professionals opinion I value. Also it's the referenced standard I am looking for as well to validate my report.

Any ideas?

Books I have, and read many times... still can't nail this down.
Steve


Inspector Steve
DSA, OSHPD, Inspector
So. California.

 

[PHovnanian]

Here's my 0.02 worth. I'm not in Calif. and therefore not intimately familiar with their seismic codes. But from an engineering point of view, adopting the piping/ductwork requirement makes sense. Structurally, an unsupported bend (whether pipe or conduit) is subject to the same forces and potential damage. After all, EMT is just a pipe full of wires.

DSAsteve, what is the exact SMACNA requirement for distances from beginning/end of sweep to the required support? Is that the 12" you cited above? Its possible that an installation where one support can be located within this maximum distance from both ends of the bend could meet the code language. Particularly for small radius bends (in 3/4 and 1" EMT for example)

 

[DSAsteve]

PHovnanian,
Thank your for your reply. While the Electrical plans reference SMACNA for seismic and attachment, The SMACNA book (that I have) dosen't get into references regarding attachment....

You asked,
"what is the exact SMACNA requirement for distances from beginning/end of sweep to the required support?"

That is a ELE CODE answer, every 10'.

SMACNA, (from memory, as my book/s are in my office), 'when the pipe, conduit or duct changes directions'.

Which would be at each end of the sweep (approx 12" on a 1" conduit). Or within 18" of a 90* fitting on pipe, or duct.

further....
Regarding this issue, the ele contractor did get a response from the SE on Friday afternoon.

The SE stated, "attachments shall follow SMACNA, NUSIG, or other accepted industry standardized guidelines. It is the Contractors' responsibility to demonstrate compliance with such standards."

I do not have a NUSIG book...someday I suppose I will. I haven't found any free info online that address this as well.

Your thoughts?

Inspector Steve
DSA, OSHPD, Inspector
So. California.

 

[davidbeach]

SMACNA deals with thrust. NEC anchorage requirements deal with gravity loads. I'd think that for small conduits the thrust anchorage would be taken care of by providing the NEC required anchorage.

 

[PHovnanian]

Sadly, the electrical code (NEC) doesn't deal with the position of supports w.r.t. sweeps or bends. As long as there is one support every 10 feet, a bend halfway in between two supports would create a 3.5 foot 'beam' secured at one end, free to swing back and forth at the other. That's what SMACNA seems to me to be addressing.

Common sense would dictate securing such an unsupported bend. It would also suggest that something like 1" conduit probably doesn't need to be supported at both ends of a bend or sweep. What about one support halfway through the bend? I wouldn't second guess the standards unless they give you some leeway in securing conduit at or within X inches of either end of a bend. If the distance along that bend is less than X, one might assume that a clamp at one end of said bend is within X of the other and satisfies that requirement as well. But then I'm playing with semantics and since I don't have SMACNA here, or any experience in dealing with its enforcers, I hesitate to recommend such methods of weaseling out of putting in a few more clamps.

 

[DSAsteve]

David, Your point is well taken. All is fine until seismic shaking begins. (Seismic zone 4, per 2001 CBC). EMT moves around creates some thrust, comes apart at the compression fittings, detaches at the straps, (because it attached to OSB), cuts through the insulation at the end of the conduit, shorts out...


PH, "Weaseling"... haha, there are gray areas. I am the type of person to utilize common sense. I am also the type of person who only wants fair. This will probably become a compromise. I want safe and secure.

The Schools in California are built to become a Sanctuary for the local populace in case of an emergency. The hospitals are built to a higher standard than that... In case the schools collapse.

Thanks, both of you...sl

Inspector Steve
DSA, OSHPD, Inspector
So. California.

 

[WoodrowJWeen]

PHovnanian, your comment about pipes with wires remids me of the Three Stooges short A Plumbing We Will Go where Curly utters the line "Hey, no wonder the water don't work, this pipe's filled up with wires."

Seriously though, I've seen studies that showed that in earthquakes, set screw type EMT fittings actually held together better than compression type.

 

[DSAsteve]

...."hey Moe...yuk, yu, yuk."

And flex holding better than EMT....

Inspector Steve
DSA, OSHPD, Inspector
So. California.

 

[EEJaime]

DSASteve,
The code reference for supporting conduit is in CEC 358 Electrical Metallic Tubing:Type EMT. Specifically 358.30(A)Securely Fastened.EMT shall be securely fastened in place at least every 3 , (10 ft). In addition, each EMT run between termination points shall be securely fastened within 900 mm, (3 ft.) of each outlet box, junction box, device box, cabinet, conduit body or other tubing termination.".
Thank you,
EEJaime

 

[DSAsteve]

EE, thank you!

And some other at

http://www.tipmaster.com/images/thumbsup2.giftachment

info in there for FMC.

Inspector Steve
DSA, OSHPD, Inspector
So. California.

 

[PHovnanian]

And flex holding better than EMT....

How did flex get into this thread? Don't try using the EMT support requirements for flex. Its a different animal entirely.