No. You can have conductors that pass through a box without terminating in the box.Originally Posted by Chris Padilla
Yep. See above.Originally Posted by Chris Padilla
You don't need to. Being the somewhat anal type about things like that, I'd probably use some of the plastic cable clamps to keep the "through" wires tucked to the sides of my boxes. I know how much you like pictures, so what I mean are these things.Originally Posted by Chris Padilla
As much as you ever do.Originally Posted by Chris Padilla
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Back to derating, and some background info:
From NEC table 310.15(B)(2)(a):
<table border="1" width="50%">
<caption>Adjustment Factors for More Than Three Current-Carrying Conductors in a Raceway or Cable</caption>
<tr><th width="25%">#Current Carrying Conductors</th><th width="25%">Derating Factor</th></tr>
<tr><td>1 - 3</td><td>100% (no derating)</td></tr>
<tr><td>4 - 6</td><td>80%</td></tr>
<tr><td>7 - 9</td><td>70%</td></tr>
<tr><td>10 - 20</td><td>50%</td></tr>
</table>
Unadjusted Ampacity for #10 THHN/THWN @90° = 40 amps.
You can run up to (3) 30 amp/240v circuits through a run of conduit, wired with #10 THHN/THWN.
You can run up to (10) 20 amp/120v circuits through a run of conduit, wired with #10 THHN/THWN.
You can run up to (3) mixed 30 amp/240v and 20 amp/120v circuits. It's only 3 because the 240v circuits(s) can only withstand 80% derating.
Put 8 CCC's in a conduit and you're looking at 70% derating which would drop the ampacity of the #10 to 28 amps. That's no problem for the 120v/20 amp circuits, but that causes a problem for the 30 amp 240v circuit. To further confuse things, there is a rule that says you can round up to the next standard breaker size (which would be 30 amps), even if the derated ampacity is 28 amps. That means you could run (4) 30-amp circuits with wire derated to 28 amps but protected by a 30 amp breaker. Confused yet? If you run a multiwire circuit, the neutrals don't count. If you're running in a basement or garage where you need GFCI for the 120v receptacles, you need separate neutrals which do count. Confused now?
The simplest thing would probably be to run 2 sets of conduit. Run 1 for 120v circuits and 1 for 240v circuits. You could run basically as many 120v circuits as you need in the "120v conduit" and up to (3) 30-amp/240v circuits in the "240v conduit". I say (3) 240v circuits because an AHJ can't argue that you've exceeded the derated ampacity of the #10, even if 240-3(b)(1) let's you. You could do the install so the conduit runs are close to each other with your outlet boxes in neat clusters.
Figure out how many circuits you want to run and we'll talk what size conduit you should run.
Holler if any of this doesn't make sense.
Rob