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    afscme's Avatar
    afscme Posts: 23, Reputation: 4
    New Member
    		  
    #1

    Jan 6, 2010, 07:18 PM
    EMT sizing
    Question concerning the use of 1” or 1 ¼” EMT. I’ve referenced the NEC tables for conduit fill, but I’m concerned about the ease of the wire pull, and the amp/derating factor, which I am not that familiar with, or if it even applies. Local code requires conduit. This is the set up:
    1. Apprx. 11 foot run between service disconnect and panelboard.
    2. Two 90 degree bends
    3. 100 amp service
    4. Feeders #4 copper labeled THHN
    5. Bonding #8 insulated labeled THHN

    So, for the above application- 1” or 1 ¼” emt? Thanks.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #2

    Jan 6, 2010, 07:26 PM

    I would go with 1¼". 1" is legal but pushing it with two 90's.
    You'll likely be able to pull it in by yourself with 1¼". With 1" you'll definitely need help.
    KISS's Avatar
    KISS Posts: 12,510, Reputation: 839
    Uber Member
    		  
    #3

    Jan 6, 2010, 08:11 PM

    If that conduit is outside which I assume it is make sure the wire is THWN. Many times the wire is dual marked THHN/THWN.
    afscme's Avatar
    afscme Posts: 23, Reputation: 4
    New Member
    		  
    #4

    Jan 6, 2010, 08:30 PM

    I like things easy so the 1 1/4" it is. Yes, the wire is dual marked THWN-2 or THHN
    donf's Avatar
    donf Posts: 5,679, Reputation: 582
    Printers & Electronics Expert
    		  
    #5

    Jan 7, 2010, 08:08 AM

    Why are you using #4 cable? If you selected this cable size because of T 310.15 in the NEC you need to be aware that this is for service entrance only.

    If you are using this amperage to feed a sub-panel then you select the required cables size based on T 310.16.
    stanfortyman's Avatar
    stanfortyman Posts: 5,598, Reputation: 279
    Electrical & Lighting Expert
    		  
    #6

    Jan 7, 2010, 02:48 PM

    Don, many areas still allow the use of 310.15(B)(6) for feeders as well as service entrance, and rightfully so IMO.
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