multiple current carrying conductors in a single racway (loading the boat)

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follybeacher said:
My question is a high level estimating question, not a granular engineering question. I understand how to calculate available fill per Ch. 9 perform adjustment factors per 310.15(B)(2)(a). When required to perform these calcs, I do so. That's not the question...

The question is what rules can an estimator most always apply to reduce cost in regards to 'loading the boat'? I build receptacle assemblies with an average conduit length to reach a 4sq box. Then I group 3 together and sending them to the respective panel. My rule (which I'm trying to expand on) is always using 3 ckts per homerun.

Can I apply other rules without having to perform engineering calcs? Time is short these days and I want to be as competitive as code compliantly possible.

I made a quick sketch to show you what's in a typical assembly and the 4sq/homerun I'm wheeling off. (This sketch is drawn as if they're dedicated ckts :roll:)

View attachment 21041
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The bottom line is that every estimate is unique. In a standard office situation with MC allowed, 15 feet of MC with every receptacle assembly, 12 feet of 12-3 for every switch, 10 feet for every light fixture and I roll the 3 way witches and put a 12-3 in between them. Then I use 3 circuits per home run just like you. If I want to get a little lower, I will use 4 home runs in a conduit which is still allowed. Home runs can be in the slab in PVC to get lower. But I usually use three. I run the home run to about the center of the three circuits use a box and I am done. The problem is when your receptacle density changes or you want to be as low as possible. Also if you are using conduit no MC allowed. I have been doing it for years and if I want any accuracy in my estimate, I just roll it. For conduit I will sketch out a run and roll. I set an add for 8 feet (assume 9 foot ceiling) and add 8 plus eight for any run that jumps two walls or a door. I don't add for receptacles on the same wall or an adjacent wall. But it takes time.
 
acin said:
Would 3 hots need a 3 phase system for mwbc?
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Yes. Here's the Article 100 definition:

Branch Circuit, Multiwire. A branch circuit that consists of two or more ungrounded conductors that have a voltage between
them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and
that is connected to the neutral or grounded conductor of the system
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