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

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 )

2. I do not do estimating, but I have a question.

With the common disconnecting means rule (handle ties or multi pole breakers) for MWBCs how are you incorporating full boats into your estimate rules?

3. Why not group 2 multi-wires together.. (2 sets of Black, Red, Blue respectively)? 9-#12s in a 3/4" pipe, then you can continue to pipe closer to their locations. I'm jumping a bit at we are considering 120/208.

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4. Originally Posted by jumper
I do not do estimating, but I have a question.

With the common disconnecting means rule (handle ties or multi pole breakers) for MWBCs how are you incorporating full boats into your estimate rules?
A 3 pole breaker costs about 3 times what 3 single poles cost. I assume that would be taken into account but it still beats the extra labor and material of non-mwbc's. I had that handle tie rule.

I agree with knight, 9 ccc is the magic number for 14 and 12, but that is 3 full boats typically.

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I'm hesitant to answer questions on this forum in the presence of such knowledgeable members, but here goes...

In my sketch I do share a ground but each circuit has a dedicated neutral thus not a MWBC and no need for handle ties. Typically the specs will state "no shared neutrals" which makes this crystal clear. If I wanted to really be aggressive and specs did not prohibit then I would qualify shared neutrals and wheel the homeruns as such.

Never do I takeoff utilizing shared neutrals / MWBCs... I could ask other seasoned estimators if I should be? That would certainly save labor and materials?

6. How deep is you 4" box? A standard 1.5" deep 4" box is too small for 13-#12's.

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Originally Posted by follybeacher
I'm hesitant to answer questions on this forum in the presence of such knowledgeable members, but here goes...

In my sketch I do share a ground but each circuit has a dedicated neutral thus not a MWBC and no need for handle ties. Typically the specs will state "no shared neutrals" which makes this crystal clear. If I wanted to really be aggressive and specs did not prohibit then I would qualify shared neutrals and wheel the homeruns as such.

Never do I takeoff utilizing shared neutrals / MWBCs... I could ask other seasoned estimators if I should be? That would certainly save labor and materials?
If the specs say "no shared neutrals" then what you are doing is correct. If you want a full boat with 6 circuits with no shared neutrals, then you get into derating issues, wire size and conduit size...so yes...the cost goes up.
However, for long home runs there is a point where it becomes a savings.

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Originally Posted by infinity
How deep is you 4" box? A standard 1.5" deep 4" box is too small for 13-#12's.
For a homerun I would typically figure a 4x2-1/8 rather than a 4x1-1/2

Originally Posted by electrofelon
A 3 pole breaker costs about 3 times what 3 single poles cost...
this shouldn't be forgotten. thank you

Originally Posted by cdslotz
If the specs say "no shared neutrals" then what you are doing is correct. If you want a full boat with 6 circuits with no shared neutrals, then you get into derating issues, wire size and conduit size...so yes...the cost goes up.
However, for long home runs there is a point where it becomes a savings.
If the specs don't prohibit this, under what circumstance would this be acceptable? Could I pack in 6 circuits into a 3/4" (6#12H, 2#12N, 1#12G, 3/4"C)? I suppose there would be de-rating, so should to simplify maybe I just use 10's? That would save an entire 3/4" raceway homerun.

These are the tricks I'm looking to identify in this post. Something I can universally apply to some or most takeoffs.

9. Originally Posted by follybeacher
For a homerun I would typically figure a 4x2-1/8 rather than a 4x1-1/2

this shouldn't be forgotten. thank you

If the specs don't prohibit this, under what circumstance would this be acceptable? Could I pack in 6 circuits into a 3/4" (6#12H, 2#12N, 1#12G, 3/4"C)? I suppose there would be de-rating, so should to simplify maybe I just use 10's? That would save an entire 3/4" raceway homerun.

These are the tricks I'm looking to identify in this post. Something I can universally apply to some or most takeoffs.
If you are sharing nuetrals then you could get nine 20A circuits in a 3/4” EMT, derate and still use #12. I usually use stranded or use 1” EMT.

9 hots, 3 neutrals, and 1 EGC. Code wise you can use the EMT as an EGC.

10. Originally Posted by jumper
If you are sharing nuetrals then you could get nine 20A circuits in a 3/4” EMT, derate and still use #12. I usually use stranded or use 1” EMT.

9 hots, 3 neutrals, and 1 EGC. Code wise you can use the EMT as an EGC.

I would just add that there is the "nonlinear load" thing potentially making the neuter a CCC, but everyone pretty much ignores that for branch circuits, in my experience.

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