18AWG DC Cables "Incapable of Transmitting Vapors"

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cowski

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Does anyone know how to determine if a shielded DC cable is incapable of transmitting vapors? 501.15(D)(3)

Is this something you contact the manufacturer about? Or does anyone advertise this? Is there a certain rating?

I'm trying to decide if I need to cut the outer sheath and shielded off my cables. I guess the answer is yes, unless I can verify
 
I can tell you that there is no cable Type that has been tested and certified to be incapable of transmitting gases and vapors through the core. But before you start cutting the outer sheath and shielding, see Section 501.15(D)(1) Exception. Otherwise, you actually have a Section 501.1(D)(2) AND its Exception application
 
rbalex said:
I can tell you that there is no cable Type that has been tested and certified to be incapable of transmitting gases and vapors through the core. But before you start cutting the outer sheath and shielding, see Section 501.15(D)(1) Exception. Otherwise, you actually have a Section 501.1(D)(2) AND its Exception application
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I always found this requirement to be curious. It seems like someone carved out a place in the code for a special type of cable that no one ever bothered to make.
 
petersonra said:
I always found this requirement to be curious. It seems like someone carved out a place in the code for a special type of cable that no one ever bothered to make.
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That is exactly what happened. I was on the CMP at the time. We were trying to set the requirements for every conceivable construction. Ar the time several manufacturers were proposing a "gas blocked" construction; however, neither they nor any NRTL were able to create an acceptable product test standard. The Sections, including 501.15(E)(2) were left in place "just in case".
 
Is type P is recognized as incapable of transmitting vapors? But it's too large for what I need.

I wonder if I can fit 30 18AWG conductors in a single conduit... It's MTW wire. I believe that's listed as TFN in the code, right? So Chapter 9 table 5 gives a diameter of 0.084. For 3/4 RMC that's a fill of 29.8095%? That seems low. Intuitively it doesn't seem like they would fit...
 
I should note Type MI probably does meet the requirement but it already has its own specific installation requirements.
 
cowski said:
Is type P is recognized as incapable of transmitting vapors? But it's too large for what I need.

I wonder if I can fit 30 18AWG conductors in a single conduit... It's MTW wire. I believe that's listed as TFN in the code, right? So Chapter 9 table 5 gives a diameter of 0.084. For 3/4 RMC that's a fill of 29.8095%? That seems low. Intuitively it doesn't seem like they would fit...
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As I mentioned, no Type is NRTL recognized.
 
cowski said:
Is type P is recognized as incapable of transmitting vapors? But it's too large for what I need.

I wonder if I can fit 30 18AWG conductors in a single conduit... It's MTW wire. I believe that's listed as TFN in the code, right? So Chapter 9 table 5 gives a diameter of 0.084. For 3/4 RMC that's a fill of 29.8095%? That seems low. Intuitively it doesn't seem like they would fit...
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MTW is not TFFN. TFFN is close to being THHN, except it is only made < 14 AWG

MTW has very thick insulation. #18 MTW is 0.111" diameter.
 
rbalex said:
That is exactly what happened. I was on the CMP at the time. We were trying to set the requirements for every conceivable construction. Ar the time several manufacturers were proposing a "gas blocked" construction; however, neither they nor any NRTL were able to create an acceptable product test standard. The Sections, including 501.15(E)(2) were left in place "just in case".
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It would appear that normal stranded wire has at least some capability to transmit gases. Wonder why it is allowed? :)
 
How would I seal the shielded cable to prevent gas from entering? Would you have an example of that by chance?

That would be a seal inside the enclosure where individual conductors exit the shielded cable, correct? I'm picturing some kind of fitting that would tighten on the cable an seal it...

I'm looking at another one of your posts on this subject now Bob. Let me read up on this a little.

cable in conduit cable end seals

anybody else have thoughts on this? why don't you try reading the code book? I’d advise you to do the same. According to you anything the AHJ happens to like - tape, cold shrink etc could be “approved” - the seal Has to block gases from entering the internal part of the cable - Sent from my...
forums.mikeholt.com
 
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