Some pics to talk about

Discussion in 'Electrical Forum discussion & Blog' started by jaxbldginspector, Feb 13, 2009.

  1. jaxbldginspector

    jaxbldginspector New Member

    Messages:
    21
    Romex 10/2 w/g
    Romex 10/3 w/g
    Romex 12/2 w/g
    Romex 12/3 w/g

    Attached Files:

  2. jar546

    jar546 In the Trades

    Messages:
    432
    Location:
    USA
    Time to do some derating calculations.
  3. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    991
    Location:
    NY State, USA
    Not if they remove that tape. ;)


    WTH is all that #10 for???
  4. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    Check out the 2008 NEC. Removing the tape doesnt matter. Its still considered bundling, you need to derate!
  5. Scuba_Dave

    Scuba_Dave Extreme DIY Homeowner

    Messages:
    885
    Location:
    South of Boston, MA
    So that's where my flux capicitor went
  6. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    991
    Location:
    NY State, USA
    How do you figure? What would you consider "maintaining spacing"?
    Last edited: Feb 14, 2009
  7. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    May be bundling in the sense you are used to is not the correct term I should use. However it would have to be derated per 2008. I personally would still say it is bundled for derating purposes there is no spacing between those conductors and would not pass the job. See below note last two paragraphs.

    334.80 Ampacity. The ampacity of Types NM, NMC, and
    NMS cable shall be determined in accordance with 310.15.
    The ampacity shall be in accordance with the 60°C (140°F)
    conductor temperature rating. The 90°C (194°F) rating
    shall be permitted to be used for ampacity derating purposes,
    provided the final derated ampacity does not exceed
    that for a 60°C (1400 P) rated conductor. The ampacity of
    Types NM, NMC, and NMS cable installed in cable tray
    shall be determined in accordance with 392.11.

    Where more than two NM cables containing two or
    more current-carrying conductors are installed, without
    maintaining spacing between the cables, through the same
    opening in wood framing that is to be fire- or draft-stopped
    using thermal insulation, caulk, or sealing foam, the allowable
    ampacity of each conductor shall be adjusted in accordance
    with Table 310.15(B)(2)(a) Exception shall not apply.

    Where more than two NM cables containing two or more
    current-carrying conductors are installed in contact with thermal
    insulation without maintaining spacing between cables the
    allowable ampacity of each conductor shall be adjusted in
    accordance with Table 310.15(B)(2)(a)
  8. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    991
    Location:
    NY State, USA
    These cables are neither:

    "through the same
    opening in wood framing that is to be fire- or draft-stopped
    using thermal insulation, caulk, or sealing foam,"


    Nor are they:

    "installed in contact with thermal
    insulation"
    .

    So the last two paragraphs do not apply.

    If they were, or are to be, then the last two paragraphs apply.
  9. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    These cables are going through the draft stopping band of the floor joist as per the building code.
    Requiring the holes to be sealed.
    Last edited: Feb 14, 2009
  10. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    991
    Location:
    NY State, USA
    Since when does a horizontal hole need to be firestopped?
  11. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    R502.12 Draftstopping required. When there is usable space
    both above and be low the concealed space of a floor/ceiling as -
    sembly, draftstops shall be in stalled so that the area of the con
    -cealed space does not exceed 1,000 square feet (92.9 m2).
    Draftstopping shall divide the concealed space into approxi -
    mately equal areas. Where the assembly is enclosed by a floor
    membrane above and a ceiling membrane below draftstopping
    shall be provided in floor/ceiling assemblies under the fol low -
    ing circumstances:
    1. Ceiling is suspended under the floor framing.
    2. Floor framing is constructed of truss-type open-web or
    perforated members.

    R502.12.1 Materials. Draftstopping materials shall not be less
    than 1/2-inch (12.7 mm) gypsum board, 3/8-inch (9.5 mm) wood
    structural panels, 3/8-inch (9.5 mm) Type 2-M-W particleboard
    or other approved materials adequately supported.
    Draftstopping shall be in stalled parallel to the floor framing
    members unless other wise approved by the building of ficial.
    The integrity of all draftstops shall be maintained

    R502.13 Fireblocking required. Fireblocking shall be pro -
    vided in wood-frame floor construction and floor-ceiling as -
    semblies in accordance with Section R602.8.

    R602.8 Fireblocking re quired. Fireblocking shall be pro -
    vided to cut off all concealed draft openings (both vertical and
    horizontal) and to form an effective fire barrier between sto -
    ries, and between a top story and the roof space. Fireblocking
    shall be provided in wood-frame construction in the following
    locations.
    1. In concealed spaces of stud walls and partitions, includ -
    ing furred spaces and parallel rows of studs or staggered
    studs; as follows:
    1.1. Vertically at the ceiling and floor levels.
    1.2. Horizontally at intervals not exceeding 10 feet
    (3048 mm).
    2. At all interconnections between concealed vertical and
    horizontal spaces such as occur at soffits, drop ceilings
    and cove ceilings.
    3. In concealed spaces be tween stair stringers at the top and
    bot tom of the run. En closed spaces under stairs shall
    com ply with Section R311.2.2.
    4. At openings around vents, pipes, and ducts at ceiling and
    floor level, with an approved material to resist the free
    pas sage of flame and products of combustion.
    5. For the fireblocking of chimneys and fire places, see Sec -
    tion R1001.16.
    6. Fireblocking of cornices of a two-family dwelling is re -
    quired at the line of dwelling unit separation.
    Last edited: Feb 14, 2009
  12. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    Please note these references are from the 2006 NC Residential Building code based on the 2002 ICC Residential Codes.
    Last edited: Feb 14, 2009
  13. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    Also if this is a basement thats not going to be finished at this time without a heating system it could be required to be insulated. Then you would have to derate for the thermal insulation also. Another possibility is insulating for sound control also would need to be derated.
  14. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    According to 310.15(B)(2)(a) more than 41 current carrying conductors have to be derated by 35% Which means you could not even put a 15A breaker on those #10's. in the first picture on the left if I counted correctly. Hard to see actually how many conductors are there.
  15. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    Sounds like some bad math.#10 would be 30 amp without derating. 30x.65=19.5 amps, which would allow a 20 amp breaker.
  16. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    991
    Location:
    NY State, USA
    You do not derate from the 30A figure. You use the actual temperature rating of the wire, which is the 90 deg C column for new THHN conductor NM cable.

    #10 NM cable is derated from 40 amps. And you do not derate by 35%. You derate TO 35%.
    Even at a 35% adjustment you CAN use a 15A breaker since we round UP to the nearest standard breaker size.
    40 x 35% = 14A = 15A breaker
  17. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,531
    Location:
    North Carolina

    It is 35% not 65%
  18. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    Thanks Speedy Petey that rounding up rule is one I forget once in a while.:eek:

    Still the caculation does come out to less than 15A. I still say the wiring routes taken are very bad practice.
  19. TedL

    TedL New Member

    Messages:
    604
    Location:
    NY Capital District
    I didn't dig out my copy of the code, but took Codeone's statement "by 35%" at face value. I just did the math check.

    I did remember the "next larger standard overcurrent device"
    :D.
  20. codeone

    codeone Code Enforcement

    Messages:
    160
    Location:
    North Carolina
    Just for debate we need to look at Article 334.80 of the NEC . Looks like it rules out the next highest breaker with two words.

    334.80 Ampadty. The ampacity of Types NM, NMC, and
    NMS cable shall be determined in accordance with 310.15.
    The ampacity shall be in accordance with the 60°C (140°F)
    conductor temperature rating. The 90°C (194°F) rating
    SHALL be permitted to be used for ampacity derating purposes,
    PROVIDED the final derated ampacity does not exceed
    that for a 60°C (1400 P) rated conductor. The ampacity of
    Types NM, NMC, and NMS cable installed in cable tray
    shall be determined in accordance with 392.11


    Now I'm not saying some AHJ's dont allow this, however it is something to consider. It may be just bad wording to give the intent. That happens sometimes.
    Last edited: Feb 16, 2009
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