Wire Size / Fixture Attachment

Discussion in 'Electrical Forum discussion & Blog' started by OscarG, Aug 19, 2007.

  1. OscarG

    OscarG New Member

    Messages:
    18
    I have installed 10 ceiling boxes in a workshop area and intend to put simple porcelain sockets on them to provide general overall lighting. Circuit wired with 12/2 NM between boxes, circuit protected at 20A. Plan to use 150W equivalent CF bulbs so no issue with heat.

    Installing the porcelain sockets I had intended to use stranded 16 THHN for pigtails on each to reduce the stress on the socket connections and actually fit the wire under the attachment screw.

    Just want to confirm that this use of reduced size wire for fixture attachment is OK. (I have seen plastic sockets with crimped on 18 pigtails.)
  2. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,566
    Location:
    North Carolina

    The size of the Overcurrent Device will mandate the size of the pigtail.

    Here you are using 20 amp Overcurrent so the pig tail MUST be #12.
  3. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    1,005
    Location:
    NY State, USA
    Mike,

    I have to disagree with you. Fixture taps follow different rules. I really do feel 402.10 applies here:

    402.10 Uses Permitted
    Fixture wires shall be permitted (1) for installation in luminaires (lighting fixtures) and in similar equipment where enclosed or protected and not subject to bending or twisting in use, or (2) for connecting luminaires (lighting fixtures) to the branch-circuit conductors supplying the luminaires (fixtures).

    Handbook commentary:
    Fixture wire is permitted to be used as a tap conductor to connect a luminaire(s) to the branch circuit conductors. There must be a transition from the branch circuit wiring method to the fixture wire tap conductors. This can be done in a junction box or other fitting that is allowed to contain splices.


    I mean think about it. Some Leviton keyless fixtures come with #18 tails as opposed to screws.
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,566
    Location:
    North Carolina
    Pete

    For years I though that the fixture could be wired based on the fixture load until I got set straight by one of the code panels at an IAEI meeting.

    The simple rule is: if we are installing the conductors we must stay with the same size or larger but never smaller. It is okay for the fixture manufacturer to use smaller conductors as when the fixture is changed the conductors will be changed also.
  5. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    1,005
    Location:
    NY State, USA
    I hate to admit it, but I DO understand that logic.
  6. seaneys

    seaneys New Member

    Messages:
    192
    Location:
    Chicago Suburbs
    I completely understand the logic, but...

    The pig tails on the ballasts from our local big box home store are 16 ga. There is not a way to change them w/o destroying the ballast. I've been scratching my head on this one for a few weeks.

    Steve
  7. Speedy Petey

    Speedy Petey Licensed Electrical Contractor

    Messages:
    1,005
    Location:
    NY State, USA
    The point is the ballast is factory assembled. You CANNOT change the wire.
    IF the ballast had screw terminals you would have to use the branch circuit wire size to those terminals.
  8. molo

    molo Member

    Messages:
    856
    Location:
    cold new york
    i see this too, doesn't it make it dangerous?
  9. hammerslammer

    hammerslammer New Member

    Messages:
    68
    Location:
    Colorado
    The 18 ga wire is serving one ballast. The branch wire might be serving 20 ballasts.
  10. OscarG

    OscarG New Member

    Messages:
    18
    Thanks for all the wisdom!

    Although my initial feeling was in agreement with Speedy Petey, that 402.10 was the applicable code, I now also see the logic differentiating factory assembled fixture wire from field wiring to a screw terminal. Looks like I go with the 12 ga pigtails to the sockets.

    As a personal aside (rant), it seems to be kind of a shame that code needs to be interpreted on the side of idiot proofing the work. In theory, anyone inside of a box should have enough knowledge to know that a pigtail is used to facilitate a connection to a fixture and is not intended as the means to connect a further extension of a branch circuit.
  11. hammerslammer

    hammerslammer New Member

    Messages:
    68
    Location:
    Colorado
    You would think but just the other day i ran into about 20 fixtures that were daisy chained with 18 guage whips. (or a mix of 18 guage and 12 guage whips because the fixture comes with the 18 ga.) Done by a licensed outfit and supposedly inspected... The whips of course are allowed to service one fixture... My boss doesn't let us daisy chain anything.
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