Sealtite - Need for additional support for short lengths

[Bompa]

Back in 2009 a member with the user name of "Masher" asked an interesting question as to whether a short length of Sealtite (say 11") could be installed with the only support being the two fittings at each end. With the changes in the wording for the 2011 NEC, I'd like to reopen that question.

Exception No. 2 to 350.30(A) has been changed seemingly taking away part of the exception for the need for flexibility issue that most people cited as justification for not supporting short lengths. The wording for the exception now reads:
"Where flexibility is necessary after installation, lengths from the last point where the raceway is securely fastened shall not exceed the following: ... " And it goes on to list the applicable lengths for various sizes, such as three feet for flex of 1-1/4" or less. (The underlined portion is the 2011 change.)

We all know there are thousands (maybe millions) of sections of unsupported flex out there. Is such an installation illegal per code? NFPA's Code Handbook makes the point that the two fittings on the end are not considered "support".

 

[jumper]

Good point. I would say it is a violation to depend on the connectors as support or securing.

ROP says:

8-61 Log #2896 NEC-P08 Final Action: Accept in Principle
(350.30(A) Exception No. 2)
_______________________________________________________________
Submitter: Jerry Grant, Plainfield, IL
Recommendation: Add new text to read as follows:
Exception: Where flexibility is necessary after installation, lengths shall not
exceed, measuring from the last fastener of the raceway, the following:
Substantiation: This is clarification of the text. The text is often applied in this
manner in the field.
Panel Meeting Action: Accept in Principle
Revise Section 350.30(A) Exception 2 to read as follows:
Exception No. 2: Where flexibility is necessary after installation, lengths
from the last point where the raceway is securely fastened shall not exceed the
following:
(1) 900 mm (3 ft) for metric designators 16 through 35 (trade sizes 1/2
through 11/4)
(2) 1200 mm (4 ft) for metric designators 41 through 53 (trade sizes 11/2
through 2)
(3) 1500 mm (5 ft) for metric designators 63 (trade size 21/2) and larger
Panel Statement: Panel changes made for clarity reasons.
Number Eligible to Vote: 12
Ballot Results: Affirmative: 12
_______________________________________________________________

 

[don_resqcapt19]

The code change for 2011 has made most industrial LFMC installations a code violation. The new wording always requires at least one support. There is nothing in the code to permit the LFMC termination to be used as a support.

 

[pfalcon]

The code change for 2011 has made most industrial LFMC installations a code violation. The new wording always requires at least one support. There is nothing in the code to permit the LFMC termination to be used as a support.

Is there anything to prohibit it being used as a support?

 

[jumper]

Is there anything to prohibit it being used as a support?

Yes. Fittings are not listed for it.

350.6 Listing Requirements. LFMC and associated fittings
shall be listed.

 

[Bompa]

I think it is interesting how different the answers above are compared to the 30 or so answers provided just two years ago. I think I?d sum up the attitude at that time as: ?What?s the big deal? It?s always been done that way and it works just fine.? Someone compared it to going 56 miles per hour is a 55mph zone.

I know that I am obligated to attempt to enforce everything that I see in the code and formal interpretations of same, but I don?t have to like everything I see there. In this case, I don?t particularly like what I see. I believe that short lengths of flex (either Sealtite or otherwise) are a great way to finish off the last 10 inches or so for a connection to motors, machine tools or other equipment that may move slightly or vibrate.

I have gone back and looked for commentary on this issue through perhaps six code handbooks. Haven't found comment #1 either one way or the other. Surely the issue must come up from time to time.

 

[tom baker]

The change for LTFC was based on the change for FMC made in the 2008 NEC.
I commonly see installations for LTFC made with no support, where there is no flexibility required, and its used just to make the installation easier. We saw an awful rule in the 08 on support between boxes less than 18" and its now gone.

 

[Bompa]

OK Tom, you “made me look”. I found five instances of your terrible rule on the 18” between boxes and they have all been deleted. I agree – terrible rule. [For those who are curious let me list them. 342.30(C) IMC; 344.30(C) RMC; 352.30(C) PVC; 355.30(C) RTRC and 358.30(C) EMT]

But in each of these cases the logic of the submitter was that straight runs up to 36” need not be suported because that is how far the code allows to the first support. To quote from the proposal that was accepted by the code panel: “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.”

So, now my question is: “Shouldn’t the same logic be applied to FMC and LFMC?” That is, no additional support should be needed if the distance is 12” or less?

 

[don_resqcapt19]

OK Tom, you ?made me look?. I found five instances of your terrible rule on the 18? between boxes and they have all been deleted. I agree ? terrible rule. [For those who are curious let me list them. 342.30(C) IMC; 344.30(C) RMC; 352.30(C) PVC; 355.30(C) RTRC and 358.30(C) EMT]

But in each of these cases the logic of the submitter was that straight runs up to 36? need not be suported because that is how far the code allows to the first support. To quote from the proposal that was accepted by the code panel: ?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.?

"CMP-8 does not necessarily agree with the submitter?s substantiation."

So, now my question is: ?Shouldn?t the same logic be applied to FMC and LFMC?? That is, no additional support should be needed if the distance is 12? or less?

There is nothing in the code to suggest that the conduit terminations are suitable as the supports for that same conduit. All the deletion of the 2008 rule for "rigid" raceways does it put is back to where we were in the 2005 and earlier codes. While not commonly enforced the current code requires a support, other than the conduit terminations, for all conduits no matter what length they are. Is this practical or done in the field, of course not, and the proposal for the rules in the 2008 code were submitted to recognize this fact. The proposal was to permit conduit of 36" or less to be supported by the conduit terminations. If was changed by the CMP to 18". The 2008 change was intended to bring the NEC into compliance with how the field installations are really installed.

In 320.30(C) for AC cable, the code rule makes it clear that the cable connector can be the required cable support in some cases. The code does not have this same language for "rigid" or flexible conduits.

While no more valid than the opinions on the meaning of the code that you will find on this site, the authors of the NEC Handbook had this to say in their commentary following section 348.30(A) Exception #4.

Exception No. 4 correlates this permission of unsupported flexible metal conduit with other wiring methods permitting the same exception throughout Chapter 3. One such example is 320.30(D)(3) for Type AC cable. FMC fittings are not considered to be a means of cable support.

(I wonder why the writers use the term "cable support" in a flexible raceway article?)

 

[Bompa]

Don,

If you look at the nearly identical comment, in the 2011 Code Handbook, for LFMC you will notice they ended with the same sentence but minus the word 'cable'. I agree, it is probably a 'typo' created by copying the comment from elsewhere in a context where 'cable' made sense.

I don't want to be a pest, but I do want to understand what you are saying. Are you saying conduits of any length need to have support beyond their connections at the end? Surely there must be some length, other than a close nipple, at which no support is needed. Or, are you saying that you agree that the common practice of no support for less than 36" is OK?

 

[Strife]

I always looked at flexibility as going both ways. Meaning: I think one DOES need 3 feet minimum of flexibility to allow for vibration. So I always installed 3 feet and a few inches with least one strap. And that's what I have asked of everyone who worked for me.
I seriously doubt 11" allows for vibration, so 11" (while might not require straps) doesn't meet the vibration criteria in my opinion.

Back in 2009 a member with the user name of "Masher" asked an interesting question as to whether a short length of Sealtite (say 11") could be installed with the only support being the two fittings at each end. With the changes in the wording for the 2011 NEC, I'd like to reopen that question.

Exception No. 2 to 350.30(A) has been changed seemingly taking away part of the exception for the need for flexibility issue that most people cited as justification for not supporting short lengths. The wording for the exception now reads:
"Where flexibility is necessary after installation, lengths from the last point where the raceway is securely fastened shall not exceed the following: ... " And it goes on to list the applicable lengths for various sizes, such as three feet for flex of 1-1/4" or less. (The underlined portion is the 2011 change.)

We all know there are thousands (maybe millions) of sections of unsupported flex out there. Is such an installation illegal per code? NFPA's Code Handbook makes the point that the two fittings on the end are not considered "support".

 

[don_resqcapt19]

Don,

If you look at the nearly identical comment, in the 2011 Code Handbook, for LFMC you will notice they ended with the same sentence but minus the word 'cable'. I agree, it is probably a 'typo' created by copying the comment from elsewhere in a context where 'cable' made sense.

I don't want to be a pest, but I do want to understand what you are saying. Are you saying conduits of any length need to have support beyond their connections at the end? Surely there must be some length, other than a close nipple, at which no support is needed. Or, are you saying that you agree that the common practice of no support for less than 36" is OK?

I am saying that the code wording always requires a support for the conduit other than the conduit termination. I agree that the practice not to support lengths 36" or less is very common and I don't see an issue doing that....other than it is a code violation. The CMP should have accepted Ryan Jackson's proposal as it was submitted for the 2008 code. The current code it forcing inspectors to ignore a code rule.