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  1. Canadian Electrical Forum
    How should I derate cables if I intend to have more than 12 cables spaced 25-100% in a ventilated cable tray? For example, 16-3 Conductor cables spaced at 25%, would generate 2 rows of 8 conductors and this falls outside the values specified in table 5D. Would I then derate using Table 5C for...
  2. Canadian Electrical Forum
    Hello Everyone If I have an armored cable (CSA TECK 90 1000V PVC POWER CABLE, HVTECK CU 3/C 115TRXLPE TS PVC AIA PVC 5KV and 133% 35kV CSA C-L-X Type MV-105) Do I need to apply table 5C and 5D according to rule 4-004 22, 23 and 24 as applicable? Or no derating is applied because it is an...
  3. 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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. 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...
  9. 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...
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