3" Nipple Strapping

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From ROP:

8-35 Log #2201 NEC-P08 Final Action: Accept
(344.30(C))
_______________________________________________________________
Submitter: James W. Carpenter, International Association of Electrical
Inspectors
Recommendation: Delete this provision. Also, delete the clause “or permitted
to be unsupported in accordance with 344.30(C)” from the last sentence of
344.30.
Substantiation: The concept of a special support rule for short lengths of
raceway run between enclosures of various sorts was added to the 2008 NEC
for the first time in the history of the NEC with negligible technical
substantiation and no evidence of loss experience, and remains at variance
from routine trade practice. The existence of a coupling now immediately
provokes a support requirement, even on a 6-inch and a 4-inch long heavy-wall
4 trade size steel nipples put together to make an 11-inch (approx.) combined
raceway. A 90 degree sweep roughly 2 trade size or larger (any centerline
length over 18 in.) now requires intermediate support. The literal text now
requires support to structure on a 3-in. nipple if even one of its ends
“encounters” a concentric knockout.
Although there are those who believe the new rule simply offers limited
relief from a rule that required all raceways to be independently supported,
routine field experience throughout the history of rigid raceway wiring methods
does not substantiate such assertions. We are unaware of any significant
attempts to require supports on short nipples. All rigid raceways under NEC
rules must be listed, including their couplings; is it conceivable that a coupling
between two segments of a short (3 ft or less) nipple so seriously degrades the
stability of the raceway that such a support is needed? Concentric knockouts in
enclosures are reviewed as part of the UL 50 process, and as anyone working
these enclosures recently should be aware, those standards have been
strengthened and these knockouts are now more robust than in previous
decades; is this the time to require even more support?
Raceways generally require support within 3 ft of terminations, and when the
entire length is just that long or shorter, no additional support should be
needed. In effect, the locknuts and bushings or connectors and locknuts at each
end are supports. This is not a new concept for the NEC: CMP 7 just added the
wording “(wiring method) fittings shall be permitted as a means of cable
support” in a number of cable articles. If carried to its logical conclusion and
routinely enforced (however unlikely), this new support rule will likely drive
the market in the direction of cabled wiring methods without any technical
justification.
It should be remembered that supports to structure are not infallible. Many
raceways hang from threaded rod of indefinite length every 10 ft or so and
within 3 ft (5 ft. in some cases) of enclosures, depending on the specific rules
for the size and character of the supported raceway. Such support clearly meets
the rules in this section, but would it add anything to a nipple between
enclosures? Further, even when rigid supports such as one-hole clips are used,
the raceway beyond the last clip can have an indefinite number of couplings
and enter the center knockout of an indefinite number of concentric knockouts;
how is this arrangement so inherently more secure than a nipple between
enclosures? This new NEC provision was without precedent, and addressed a
nonexistent problem.
Panel Meeting Action: Accept
Panel Statement: CMP-8 does not necessarily agree with the submitter’s
substantiation. Securement requirements are found in 344.30(A).
Number Eligible to Vote: 12
Ballot Results: Affirmative: 11 Negative: 1
Explanation of Negative:
GRIFFITH, M.: See my explanation of negative vote on Proposal 8-24a.
Comment on Affirmative:
DABE, J.: See my statement for 8-24(a).


Also, rejected:

8-36 Log #3068 NEC-P08 Final Action: Reject
(344.30(C))
_______________________________________________________________
Submitter: Mike Holt, Leesburg, FL
Recommendation: Revise text as follows:
(C) Unsupported Raceways. Where oversized, concentric or eccentric
knockouts are not encountered, Type RMC shall be permitted to be
unsupported where the raceway is not more than 450 mm (18 in.) and remains
in unbroken lengths (without coupling). Such raceways shall terminate in an
outlet box, junction box, device box, cabinet, or other termination at each end
of the raceway.
Substantiation: This requirement is overly restrictive.
Panel Meeting Action: Reject
Panel Statement: See panel action on Proposal 8-35.
Number Eligible to Vote: 12
Ballot Results: Affirmative: 12
 
From 2008 ROP, the origin of 344.30(C)

8-23 Log #1346 NEC-P08 Final Action: Accept
(344.30(C))
________________________________________________________________
Submitter: Mike Holt, Mike Holt Enterprises
Recommendation: Add the following text to 344.30
(C) Unsupported raceways: Type RMC shall be permitted to be unsupported
where the raceway is not more than 900 mm (3 ft) in length and remains in
unbroken lengths (without coupling). Such raceway shall terminate in an outlet
box, junction box, device box, cabinet, or other termination at each end of the
raceway.
Substantiation: Unsupported raceways are violations of the Code that occur
everyday. As written, a 3 inch length of conduit between enclosures is required
to be supported, despite the fact that it adds little if any structural value to the
system. Quite often, particularly with conduit nipples, securing and supporting
a raceway shorter than 36 inches is not possible. Furthermore, securing and
supporting is of little value on lengths less than 36 inches where the conduit
terminates at a box on each end, where the box is installed and supported in
compliance with its applicable Code section.
This proposal is written with the parallel effect of Code sections that have
been strived for in chapter 3, and matches the numbering system used in the
Cable Articles. It also uses existing text taken from both the Cable Articles and
the Raceway Articles.
Panel Meeting Action: Accept
Number Eligible to Vote: 12
Ballot Results: Affirmative: 10 Negative: 2
Explanation of Negative:
DABE, J.: See my comment for 8-9.
HUMPHREY, D.: This proposal does not address other issues that may have
a direct impact on the durability of the electrical installation. The affects of
weight and vibration on concentric and eccentric knockouts at each end of a
three foot run between pieces of equipment, a scenario that would be frequently
encountered in many electrical installations, may compromise the strength
of the installation. The raceway having even a single point of support would
help to mitigate these deleterious affects. In addition, the RMC installation in
question may be used as an equipment grounding conductor and any loosening
that could occur would serve to compromise the equipment grounding function
of the raceway. 300.11 further requires that raceways be securely fastened in
place. I would assert that this proposal would conflict with the requirements
of 300.11. In summation, depending on connectors, double locknuts etc. to
support and secure this up to 36 in. installation especially where concentric or
eccentric knockouts are encountered is dubious at best. 36 in. should provide
ample space in which to install normal supporting and securing hardware. A
proposal involving a shorter distance and where no concentric or eccentric
knockouts are encountered may be in order.
 
Regardless of what the code says, requiring support of a piece of conduit less than three feet is ridiculous. I have never felt the need to do this and I have never been dinged for it. If I was, I would get out a piece of tie wire or a coat hanger and run it as crooked as I could to a screw on the nearest stud and call it good. Just to be difficult. Or maybe plumber's tape. They always hate that.
 
Strathead said:
Regardless of what the code says, requiring support of a piece of conduit less than three feet is ridiculous. I have never felt the need to do this and I have never been dinged for it. If I was, I would get out a piece of tie wire or a coat hanger and run it as crooked as I could to a screw on the nearest stud and call it good. Just to be difficult. Or maybe plumber's tape. They always hate that.
Click to expand...

Don't waste your time trying to support the short length, instead use the plumber's strap to secure the inspector to the nearest surface:)
 
I know, this is EMT, and the boxes are not supported, but I just wanted to share this because it is amusing.
 
dkidd said:
I know, this is EMT, and the boxes are not supported, but I just wanted to share this because it is amusing.
Click to expand...

Now I'd like to see an example where the raceways are supported, but the enclosures are not.

Other than the case of conduit bodies that don't have a way to support them independent of the raceways, I would think that all boxes would require self-supporting.
 
Carultch said:
Now I'd like to see an example where the raceways are supported, but the enclosures are not.

Other than the case of conduit bodies that don't have a way to support them independent of the raceways, I would think that all boxes would require self-supporting.
Click to expand...

I've done that though it is not code compliant, temporary outlets pre assembled - just slap them up on a wall, pole, etc with straps over the nipples between the outlet boxes.

Actually if you use the right kind of box and have at least two raceway entries - it is legal to support the box via the raceway, but has to be RMC/IMC raceway as well.
 
I find it interesting that the CMP endorsed the reasoning that requiring support within 36 inches means that no support is required for lengths less than 36".
That defies logic, but may be in accord with AHJ practice.
 
GoldDigger said:
I find it interesting that the CMP endorsed the reasoning that requiring support within 36 inches means that no support is required for lengths less than 36".
That defies logic, but may be in accord with AHJ practice.
Click to expand...
There is nothing in Code which precludes a conduit's termination from being either a secure fastening or a means of support.
 
augie47 said:
Don, Rob: I follow what you are saying and don't disagree with you on the wording.
As stated, it does appear, to me, that the Analysis interprets it differently but that is, of course, an opinion.
I doubt any of the local inspectors would reject the OPs install on "conduit support", but many might on "box support"
Click to expand...
The very fact that the inspectors don't enforce the code as currently written was cited by the CMP in their panel statement as the reason no changes are required in the section.
 
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