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  1. Conduit Temperature Derating

    NEC Code Forum
    I'm trying to settle an argument between myself and a colleague. We are designing new product. It's 3 phase WYE rated at 343A/phase. (120/208Vac) We disagree on the cable size needed in the field for installs. We agree that we need a 450A breaker, but we disagree on the cable sizing. I say...
  2. applying conduit fill and voltage drop.

    Commercial Electrical Forum
    I have 4-10 ton, 460v 3ph RTU's in a row. am wanting to hit 2- RTU's with one raceway. There would be 7 current carrying cunductors.( 2- 25 amp MCA, circuits plus a 120v service recept in each conduit) the longest run is 275'. the other is 235' I know how to calculate for VD but im sketchy on...
  3. Branch Circuit Derating

    NEC Code Forum
    Now that code requires separate neutrals for each branch circuit (unless 2P/3P breaker) how many circuits do you install in a conduit? Per Table 310.15B3a more then 10-20 current carrying conductors require a 50% adjustment factor. Since the individual neutral conductors are no longer carrying...
  4. de-rating conductors in conduit

    General Electrical Discussion
    Hi All, I have a customer who wants a transfer panel put in and we plan on moving about 16 circuits to the new transfer panel, (which will include two or three 240V circuits.) These circuits will be traveling through conduit for just over 24 inches and I am thinking I will have to de-rate each...
  5. Derating and Overcurrent Protection

    NEC Code Forum
    So I have a question about derating guys. I've recently taught myself java, and I'm building a simple wire size calc. Nothing fancy no temp adj. or anyting just for THHN/THWN-2. Let's say I'm derating for 10-20 conductors in a conduit. So my derate percentage is 50% right? Then I plug in...
  6. neutrals and derating?

    General Electrical Discussion
    when derating wires due to conduit fill, there is exceptions talking about the neutral not needing to be counted as a "current carrying conductor" if it is carrying only the unbalanced load of a multiwire circut.... so when do you not have to count the neutral as a current carrying conductor...
  7. Ampacity and deratings

    NEC Code Forum
    Hello, folks: I must take an examination on Friday and am struggling a bit with problems pertaining to ampacities and to the proper procedure for derating ampacities. I show below a sample problem and my proposed solution. I would like to know whether or not the proposed solution is correct...