Nipple support

[Jminter]

I've been told there was a section prior to 2008 or 11, that allowed for conduits under 24" to go without being strapped/securely fastened. I thought I remembered seeing a similar section in more recent editions of the code book, but for the life of me I can't find it. With that section removed, if it has been, have any of you run into an AHJ that finds fault in not strapping a conduit this length? I've got several T condulets running to some ATSes from less than a foot away, and I want to make sure it's not going to be a bigger deal than I imagine it is, before handing it off to the customer.

 

[infinity]

There was one code cycle where nipples did not require support, that section was removed in the next code cycle. Don't have access to my books right now it was somewhere around the 2005/2008 cycles. As dumb as it is support is required.

 

[kwired]

My favorite question related to this goes like: is that strap on that two foot piece of 3 inch RMC (secured to a cabinet on each end) supporting the conduit or is the conduit supporting the strap?

Stupid rule majority of the time.

 

[rcarroll]

My favorite question related to this goes like: is that strap on that two foot piece of 3 inch RMC (secured to a cabinet on each end) supporting the conduit or is the conduit supporting the strap?

Stupid rule majority of the time.

Agree. I don't enforce it.

 

[don_resqcapt19]

It was for 18" and less, and was only in the 2008 code. xxx.30(C). The original proposal was for 36", but the code making panel reduced that to 18". It was deleted because proposals for the 2011 code said that the new rule in 2008 was adding a support requirement without any technical substantiation. The problem is really that the CMP does not understand what the code language actually says. It is clear that the actual code language requires a support for a raceway no matter how short it is.

I submitted a PI for the 2020 code to permit 36" without a support, but it was rejected by the CMP. They said it restricted the judgement of the AHJ. However, if an AHJ wants to permit any length of raceway to be installed without out a support, the only way they can do that with the current code is by the use of a "special permission". That is very unlikely to happen as special permissions are required to be provided to the contractor in writing. It is unlikely that an AHJ will actually do that.

 

[infinity]

It was for 18" and less, and was only in the 2008 code. xxx.30(C). The original proposal was for 36", but the code making panel reduced that to 18". It was deleted because proposals for the 2011 code said that the new rule in 2008 was adding a support requirement without any technical substantiation. The problem is really that the CMP does not understand what the code language actually says. It is clear that the actual code language requires a support for a raceway no matter how short it is.

I submitted a PI for the 2020 code to permit 36" without a support, but it was rejected by the CMP. They said it restricted the judgement of the AHJ. However, if an AHJ wants to permit any length of raceway to be installed without out a support, the only way they can do that with the current code is by the use of a "special permission". That is very unlikely to happen as special permissions are required to be provided to the contractor in writing. It is unlikely that an AHJ will actually do that.

I don't like to bash CMP's but some of them need to take a trip out into the field every once in a while and look at things like this. :roll:

 

[LarryFine]

I don't like to bash CMP's but some of them need to take a trip out into the field every once in a while and look at things like this. :roll:

Egad, sir! That would be like suggesting that architects visit construction sites to see whether their designs can actually be built.

 

[ggunn]

Egad, sir! That would be like suggesting that architects visit construction sites to see whether their designs can actually be built.

When I designed my first sizeable (~650 kW DC) rooftop PV system the guy who was supposed to be the field supervisor for the project flaked out, so it fell to me to take his place. Not only was I able to see for myself the mistakes I had made in the design, it was my job to fix them on site. The experience made me a much better designer.

 

[Carultch]

I submitted a PI for the 2020 code to permit 36" without a support, but it was rejected by the CMP. They said it restricted the judgement of the AHJ.

This isn't like a fire safety procedure, such that it might need to be coordinated with local requirements and local stakeholders, this is the basic mechanics of how to construct a conduit run.

I could see the logic if allowing local rules to govern for a raceway in the wind and snow, but inside a building, exactly the same structural loads on the same nipple apply EVERYWHERE in the country. The rule we had in 2008 was a good rule (18" can be "unsupported" if it is any non-flexible raceways with no couplings). I don't understand why it had to be removed.

 

[don_resqcapt19]

Here is the proposal and comments that took the rule out of the code:

8-24a Log #2200 NEC-P08 Final Action: Accept
(342.30(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 342.30(C)” from the last sentence of
342.30.
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 342.30(A).
Number Eligible to Vote: 12
Ballot Results: Affirmative: 11 Negative: 1
Explanation of Negative:
GRIFFITH, M.: IEEE does not agree with the concluding statement in
submitter’s substantiation that “This new NEC provision (in the 2008 NEC)…
addressed a non-existent problem.” During the 2008 NEC cycle Panel 8 fully
considered the need for adding the section which the submitter proposes to
delete. The Panel determined that the present language was needed to clarify
that short nipples do not require additional support and that this was not
universally understood by AHJ’s, especially in remote & rural areas.
Comment on Affirmative:
DABE, J.: The base rule under.30(A) for IMC, RMC, PVC, RTRC, and
EMT, remains in force. The conduit systems shall be securely fastened within 3
feet between termination points.

 

[Adamjamma]

Based upon the last statements of what the code panel considers, the code rule does not require lengths under three feet to need secured if the boxes are supported... but the AHJ s are apparently reading it as they need supported. So, the panel does not work with the AHJ s..lol