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Thread: DLO (Diesel Locomotive Cable) and the NEC

  1. #1
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    DLO (Diesel Locomotive Cable) and the NEC

    I am hoping some of the veterans out there can give me some insight and there experiences on the use of DLO (UL listed of course) for use as building wire. The application requires large conductor sizes and some pretty tight bending radius that would make it next to impossible to install with traditional methods. The AHJ approved the design with DLO, but now they want it torn out. How have you guys resolved the following issues in the past with the AHJ:

    1. The DLO in question is UL listed as a RHW/RHH-2 cable and CT rated. Has anyone ever encountered a restricted UL label such DLO label for RHW/RHH-2 is only applicable under certain conditions? My current argument is if its is UL labeled as RHW/RHH-2 it complies with Article 310, it is allowed for use as noted within NEC Chapter 3 (NEC 310.13).

    2. Once you get above 4/o the conductor sizes get “oddball”. My design as approved interpolated between conductor sizes per the 310 Tables (i.e., 535.3MCM on Table 310.17, 75degC is 620A). Has anyone else used this methodology or did they just round down to the next published conductor size? Or has anyone tried a NEC 310.15(C) supervised calculation?

    3. This one surprise me since the original design complied with NEC 392.11(B)(3), but when the Owner threw another feeder into the mix during construction that Code section was kaput (lucky me). Now if I specified 535.3MCM, how do you resolve 392.11(B)(1) and (2)? Average the 2 conditions or throw more copper into the project and just comply with 392.11(B)(2)?

    4. Does anyone know of any UL486 or NEC nuances that says you cannot use a Class DLO or equivalent highly flexible, stranded cable termination for general wiring. I am just asking to have an answer for the AHJ in case they ask, because I can already see an argument that the terminations for DLO are only for a NEC 400 cord connection and not a NEC Chapter 3 installation, or that the UL listing is only good for factory assembled equipment.

    I have specified DLO in the past without any problems (knock on wood) but this current project has thrown all kinds of problems that I thought I had reasonably resolved in the past. Things have been fairly diplomatic so far and the last thing I want to have happen is have the AHJ use the infamous NEC 90.4 triumph card and me becoming an engineer who knows where you can get a great deal on some DLO cable :smile:

    Any insight and/or experiences will be greatily appreciated by this EE.

  2. #2
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    Quote Originally Posted by kpezzoni
    The DLO in question is UL listed as a RHW/RHH-2 cable and CT rated.
    If the cable has a listing RHW/RHH-2, you should be able to use it as that type - any other listings with non-NEC types are irrelevent. Most of the THHN/THWN wire I use also has an MTW rating on it - this doesn't mean it's somehow less suitable. It sounds though like you don't have enough bending space for a RHW/RHH installation?

    Does anyone know of any UL486 or NEC nuances that says you cannot use a Class DLO or equivalent highly flexible, stranded cable termination for general wiring. I am just asking to have an answer for the AHJ in case they ask, because I can already see an argument that the terminations for DLO are only for a NEC 400 cord connection and not a NEC Chapter 3 installation, or that the UL listing is only good for factory assembled equipment.
    Take a look at 310.8(A) in the 2008 NEC. Also take a look at Table 400.4 in the 2008 code - it lists all of the approved flexible types, and DLO is not on the list.

    P.S. - Shouldn't the '-2' above be after the wire type with the 'W' in it? Not claiming you made an error, just curious.
    Last edited by jdsmith; 04-11-08 at 12:56 PM.

  3. #3
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    Quote Originally Posted by kpezzoni
    I am hoping some of the veterans out there can give me some insight and there experiences on the use of DLO (UL listed of course) for use as building wire. The application requires large conductor sizes and some pretty tight bending radius that would make it next to impossible to install with traditional methods. The AHJ approved the design with DLO, but now they want it torn out. How have you guys resolved the following issues in the past with the AHJ:

    1. The DLO in question is UL listed as a RHW/RHH-2 cable and CT rated. Has anyone ever encountered a restricted UL label such DLO label for RHW/RHH-2 is only applicable under certain conditions? My current argument is if its is UL labeled as RHW/RHH-2 it complies with Article 310, it is allowed for use as noted within NEC Chapter 3 (NEC 310.13).
    Use it all the time for just such applications. As long as it is listed RHW/RHH-2, and you have it terminated with the proper compression connectors listed for such cable your AHJ has no grounds to reject it.

  4. #4
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    I use DLO all the time, although I actually refer to it as RHW/RHH-2 with the bending properties of DLO, so the AHJ doesn't get nervous.
    I use table 300.16 and always use the standard size row the is appropriate for the DLO rounded down to the nearest standard ampacity.
    Ron

  5. #5
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    This thread takes me back to my days as a locomotive electrician...Thank God that's over!
    *Sometimes I wonder why the frisbee keeps getting bigger...and then it hits me!

  6. #6
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    There are some legitimate issues with using diesel cable. You normally cannot use regular equipment lugs because they are not listed for the many fine strands diesel cable is made from. You need to terminate the cables with special compression lugs listed for this purpose.

    Incidentally, Marathon has recently come out with a line of distribution blocks UL listed for use with this type of cable.

    There have been a number of fires that resulted from using this kind of cable and terminating them on the normal lugs equipment is supplied with.
    Bob

  7. #7
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    Quote Originally Posted by kpezzoni
    I am hoping some of the veterans out there can give me some insight and there experiences on the use of DLO (UL listed of course) for use as building wire. The application requires large conductor sizes and some pretty tight bending radius that would make it next to impossible to install with traditional methods. The AHJ approved the design with DLO, but now they want it torn out. How have you guys resolved the following issues in the past with the AHJ:

    1. The DLO in question is UL listed as a RHW/RHH-2 cable and CT rated. Has anyone ever encountered a restricted UL label such DLO label for RHW/RHH-2 is only applicable under certain conditions? My current argument is if its is UL labeled as RHW/RHH-2 it complies with Article 310, it is allowed for use as noted within NEC Chapter 3 (NEC 310.13).

    2. Once you get above 4/o the conductor sizes get “oddball”. My design as approved interpolated between conductor sizes per the 310 Tables (i.e., 535.3MCM on Table 310.17, 75degC is 620A). Has anyone else used this methodology or did they just round down to the next published conductor size? Or has anyone tried a NEC 310.15(C) supervised calculation?

    3. This one surprise me since the original design complied with NEC 392.11(B)(3), but when the Owner threw another feeder into the mix during construction that Code section was kaput (lucky me). Now if I specified 535.3MCM, how do you resolve 392.11(B)(1) and (2)? Average the 2 conditions or throw more copper into the project and just comply with 392.11(B)(2)?

    4. Does anyone know of any UL486 or NEC nuances that says you cannot use a Class DLO or equivalent highly flexible, stranded cable termination for general wiring. I am just asking to have an answer for the AHJ in case they ask, because I can already see an argument that the terminations for DLO are only for a NEC 400 cord connection and not a NEC Chapter 3 installation, or that the UL listing is only good for factory assembled equipment.

    I have specified DLO in the past without any problems (knock on wood) but this current project has thrown all kinds of problems that I thought I had reasonably resolved in the past. Things have been fairly diplomatic so far and the last thing I want to have happen is have the AHJ use the infamous NEC 90.4 triumph card and me becoming an engineer who knows where you can get a great deal on some DLO cable :smile:

    Any insight and/or experiences will be greatily appreciated by this EE.
    I use DLO-TC all the time for large transformers secondary conductors.

    You may want to ask the specific reasons why the instalaltion does not meet the NEC. Ask ofr specific refereces in the Code.

    If it has to do with the ampacity of the oddball conductor sizes then you can ask a PE to approve the design and you will be in compliance with that provision of the Code. You may also just use the manufacturer's listing of the amerage rating if that is listed with a Code reference as to the installation method (three conductors in free air, whatever), because it was calculated by an engineer therefore meets the COde.

  8. #8
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    Quote Originally Posted by jdsmith
    If the cable has a listing RHW/RHH-2, you should be able to use it as that type - any other listings with non-NEC types are irrelevent. Most of the THHN/THWN wire I use also has an MTW rating on it - this doesn't mean it's somehow less suitable. It sounds though like you don't have enough bending space for a RHW/RHH installation?



    Take a look at 310.8(A) in the 2008 NEC. Also take a look at Table 400.4 in the 2008 code - it lists all of the approved flexible types, and DLO is not on the list.

    P.S. - Shouldn't the '-2' above be after the wire type with the 'W' in it? Not claiming you made an error, just curious.
    You're right, in haste to post my message I should have written RHH/RHW-2, my bad. I am not too concerned (or should I say I wasn't) with the DLO designation when the cable is UL labelled as RHW-2, or valid listing under Article 400 since I would not comply with 400.8(1) and (6). At this point I am more worried there is something buried within the UL labelling of high press connector suitable for DLO that would void its use in the Code under a Chapter 3 installation.

  9. #9
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    Quote Originally Posted by weressl
    I use DLO-TC all the time for large transformers secondary conductors.

    You may want to ask the specific reasons why the instalaltion does not meet the NEC. Ask ofr specific refereces in the Code.

    If it has to do with the ampacity of the oddball conductor sizes then you can ask a PE to approve the design and you will be in compliance with that provision of the Code. You may also just use the manufacturer's listing of the amerage rating if that is listed with a Code reference as to the installation method (three conductors in free air, whatever), because it was calculated by an engineer therefore meets the COde.
    The biggest hurdle right now is the claim by the AHJ is they are not accepting the mfgr's the UL label and the oddball size is not listed within the 310 Tables. :confused: One would think that if the design is stamped and sealed and the plan checker approved it, then the inspector should not have a problem.

    Another hurdle I need to address is the gap in 392.11 and attempting to argue the point that I shouldn't need to round the allowable ampacity down to 65% which well likely require another set of conductors, but then again this might be a non-issue if a 500MCM table value is used.

    Guys, thanks for the input so far! :smile:

  10. #10
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    Quote Originally Posted by kpezzoni
    ...At this point I am more worried there is something buried within the UL labelling of high press connector suitable for DLO that would void its use in the Code under a Chapter 3 installation.
    Repeating to self: it's RHH/RHW not DLO, it's RHH/RHW not DLO, it's RHH/RHW not DLO:smile:

    Do you have the brand and part number of the hypress connectors available? The UL white book is available online, and that combined with the manufacturer's data sheet should make your case for you - or the inspector, depending on how things are listed. Shouldn't be too hard to dig up though.

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