330.30(C) - MC Cable Securing/Supporting

[CodyBost]

330.30(C) allows for "Horizontal runs of Type MC Cable installed in wooden or metal framing members or similar supporting means shall be considered supported and secured where such support does not exceed 6-ft intervals."

In applying knowledge from my interpretation from previous code cycles and other sections of the current, such as 300.4(A) & 300.4(B), it is my belief that the phrase "wooden or metal framing members or similar supporting means" is not intended to include structural steel members of commercial buildings (I-beam and bar joist). As such, I interpret this to mean that MC cable installed on or above bar joists in decking fluts, at 6' intervals would be adequately supported, but still need to be secured in place.

What are the forum's thoughts?

 

[iwire]

I disagree with you and will mention the company I work for installs miles and miles of MC across the structural members you mention without securing the cable to each one.

 

[iwire]

By the way, welcome to the forum. I hope I did not come across like a jerk in my post above.

 

[CodyBost]

Thanks for the welcome! I've always valued the forum as a resource for insight. By joining I was hoping to resolve my current conflict and contribute to the questions and dilemmas of others.

You didn't present as a jerk. Just because your company does it that way, doesn't necessarily mean that it is correct.

To provide further thoughts, if one were to reference the 2002 NEC on this topic (70:2002-330.30(A) and 70:2002-300.4), has the intent of the code changed?

 

[iwire]

Just because your company does it that way, doesn't necessarily mean that it is correct.

Well that I agree with you on 100%.


But beyond that in my opinion none of the code sections you have cited (and none you have not) require anything more than supporting the MC by structural members.

I can also tell you that in 30 something years I have never seen an inspector dispute this in CT, RI, MA, NH.

 

[infinity]

330.30(C) allows for "Horizontal runs of Type MC Cable installed in wooden or metal framing members or similar supporting means shall be considered supported and secured where such support does not exceed 6-ft intervals."

In applying knowledge from my interpretation from previous code cycles and other sections of the current, such as 300.4(A) & 300.4(B), it is my belief that the phrase "wooden or metal framing members or similar supporting means" is not intended to include structural steel members of commercial buildings (I-beam and bar joist). As such, I interpret this to mean that MC cable installed on or above bar joists in decking fluts, at 6' intervals would be adequately supported, but still need to be secured in place.

What are the forum's thoughts?

Also keep in mind if these MC cables are installed below a roof deck then they cannot be installed within 1.5" of the underside of the roof decking. That usually prohibits running them within the flutes or over bar joists and I beams.

 

[iwire]

Also keep in mind if these MC cables are installed below a roof deck then they cannot be installed within 1.5" of the underside of the roof decking. That usually prohibits running them within the flutes or over bar joists and I beams.

Yes that changed things a bit but now we just run them on the bottom of the truss.

There is normally enough space to run on top of I-beams still

 

[ActionDave]

.....In applying knowledge from my interpretation from previous code cycles and other sections of the current, such as 300.4(A) & 300.4(B), it is my belief that the phrase "wooden or metal framing members or similar supporting means" is not intended to include structural steel members of commercial buildings (I-beam and bar joist). As such, I interpret this to mean that MC cable installed on or above bar joists in decking fluts, at 6' intervals would be adequately supported, but still need to be secured in place.

What are the forum's thoughts?

It seems like you are narrowing the terms "wooden or metal framing members" to only mean studs. That's just not true.

A joist is a framing member, a truss is a framing member, a beam is a framing member, a post is a framing member, a header is a framing member,..... anything that makes up the frame of the building is a framing member.

There are a lot of things that are not framing members but their use or placement most often comes after the framing members have been installed, each according to its purpose.

 

[iwire]

Cody, what do you see as a safety issue leaving the cables supported but not secured?

 

[CodyBost]

Cody, what do you see as a safety issue leaving the cables supported but not secured?

I see no real safety issue associated with the cables being unsecured. I also do not see a real safety concern in the requirement to support MC cable within 12" of a box when it will be concealed within a finished wall, but the requirement still exists.

 

[CodyBost]

It seems like you are narrowing the terms "wooden or metal framing members" to only mean studs. That's just not true.

A joist is a framing member, a truss is a framing member, a beam is a framing member, a post is a framing member, a header is a framing member,..... anything that makes up the frame of the building is a framing member.

There are a lot of things that are not framing members but their use or placement most often comes after the framing members have been installed, each according to its purpose.

If you go back to the 2002 edition of the code it reads as follows:

330.30 Securing and Supporting. Type MC cable shall be supported and secured at intervals not exceeding 6 ft.
(A) Horizontal Runs Through Holes and Notches. In other than vertical runs, cables installed in accordance with 300.4 shall be considered supported and secured where such support does not exceed 6 ft intervals.

For reference the headings under 300.4 are as follows:
300.4 Protection Against Physical Damage
(A) Cables and Raceways Through Wood Members
(1) Bored Holes
(2) Notches in Wood
(B) Nonmetallic-Sheathed Cables and Electrical Nonmetallic Tubing Through Metal Framing Members
(1) Nonmetallic-Sheathed Cable
(2) Nonmetallic-Sheathed Cable and Electrical Nonmetallic Tubing
(C) Cables Through Spaces Behind Panels Designed to Allow Access
(D) Cables and Raceways Parallel to Framing Members
(E) Cables and Raceways Installed in Shallow Grooves
(F) Insulated Fittings

As one can deduce from these headings, the combination of MC cable and steel structural members have no place in 300.4 (2002) and as such, the combination is also not considered "supported and secured" per 330.30(A) (2002).

The language was changed in 2005, and I've previously quoted the current 330.30(C) which is the basis of this discussion. I believe the previous language did not intend to include bar joists, spaced 6-ft apart, as sufficient to consider the cable "supported and secured." Although the language has changed, I feel that the intent of this code section remains the same.

I submitted a Technical Question to NFPA on this topic and received the following answer: "Type MC cable shall be considered supported by bar joists at intervals not exceeding 6'. The cable does still need to be secured."

At least one person agrees with me... I am feeling that those that do not, are reading the plain language and not realizing the intent.

 

[iwire]

At least one person agrees with me... I am feeling that those that do not, are reading the plain language and not realizing the intent.

The plain language is all that can be enforced.

I personally think you have assumed you know the intent when really none of us beyond the CMP no the intent

 

[CodyBost]

I personally think you have assumed you know the intent when really none of us beyond the CMP no the intent

Yes, I think that I understand the intent, but you're correct, without any insight into the CMP's decision to choose this language, my belief is an assumption. Obviously most seem to disagree with my position, so I will accept that my position is largely viewed as incorrect and I will move forward with the consensus' position.

iwire, thanks for hashing this out with me. I'm a little disappointed it was mostly a two-way discussion, though.

 

[ActionDave]

iwire, thanks for hashing this out with me. I'm a little disappointed it was mostly a two-way discussion, though.

I did my best, but if I don't go to work and pay some attention to my wife when I get home I'll end up either with no house or thrown out of my house.

 

[david]

Yes, I think that I understand the intent, but you're correct, without any insight into the CMP's decision to choose this language, my belief is an assumption. Obviously most seem to disagree with my position, so I will accept that my position is largely viewed as incorrect and I will move forward with the consensus' position.

iwire, thanks for hashing this out with me. I'm a little disappointed it was mostly a two-way discussion, though.

When supported by a notch or a hole not exceeding six ft. it is also secured in place by the same thing that supports the cable.

When supported by a bar joist all you can say as fact is the cable is supported and is not run through a notch or hole.
It can certainly be debated if the cable is secured in place.

The rule requires the cable to be supported and secured in place. And since secured is debatable it?s going to be up to the authority as to what secured means when the cable is supported by bar joist.

 

[ActionDave]

I am a simple guy, six feet tall. I am running MC across ceiling joists and the spacing of the joists is less than or equal to my arm span. I'm happy and satisfied that things are okay.

Over thinking things too much has a severe negative impact on my domestic tranquillity.

 

[CodyBost]

When supported by a bar joist all you can say as fact is the cable is supported and is not run through a notch or hole.
It can certainly be debated if the cable is secured in place.

This is my thought precisely. We have all pulled MC cable through wooden and metal studs; you're lucky to pull it through more than three or four without it getting hung up. You can pull MC cable across bar joists all day long without it getting caught, and if it does, it is nothing that a good firm tug won't fix.

 

[iwire]

This is my thought precisely. We have all pulled MC cable through wooden and metal studs; you're lucky to pull it through more than three or four without it getting hung up. You can pull MC cable across bar joists all day long without it getting caught, and if it does, it is nothing that a good firm tug won't fix.

And how does any of that show a need to secure it?

 

[david]

I thought it was given that the code section required the cable to be secured.

I was understanding the question to be if the cable is laid on bar joist (supported by bar joist ) if that fulfilled the requirement that the cable be secured.

Some might say it depends on where on the bar joist the cable is laid In the V part of the bar joist or on the flat part of the bar joist.

Buying the MC cable reverse wound helps with cable hanging up when pulled through metal studs

 

[iwire]

It is my opinion and apparently the opinion of inspectors all over this area that the cables ruining across truss, beams etc. do not have to be ssecured to those items only supported

We still have to secure it at the enclosure it enters.

And I agree direction of the MC makes a huge difference in ease of pulling.