Conduit fill.

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Dsg319

Dsg319

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West Virginia
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Wv Master “lectrician”
When calculating conductors of different sizes for conduit fill, at what decimal do you round up or down? I know for conductors of all the same size if it is 0.8 you round up.
 

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If you calculate a raceway can hold 6.7 conductors you are limited to 6 conuctors.

If you calculate a raceway can hold 6.8 or 6.9 conductors you can install 7.

different sizes just doesn't work out, If you have a 10 AWG and remaining room for 5.8 6 AWG's can you add an additional 6? an additional 10? This may seem simple but what if you have even more variety of sizes of conductors involved. Which one do you apply the fractional figure to when rounding up?
 
LarryFine said:
I use an online conduit-fill calculator.
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I’ve got one as well, though we usually work off of a set of prints where everything is already figured out and we just gotta put it together. And had been a while since I’ve done a calculation and still nice to know In my head how to do on paper for my own sake lol.
 
kwired said:
If you calculate a raceway can hold 6.7 conductors you are limited to 6 conuctors.

If you calculate a raceway can hold 6.8 or 6.9 conductors you can install 7.

different sizes just doesn't work out, If you have a 10 AWG and remaining room for 5.8 6 AWG's can you add an additional 6? an additional 10? This may seem simple but what if you have even more variety of sizes of conductors involved. Which one do you apply the fractional figure to when rounding up?
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If I understand your question correctly you could only add an additional 10awg of the same size with the fraction of 0.8 or greater.
 
If they are all the same size you are likely to use Table C which takes the .8 factor into consideration so it's kinda one of those nice thing s to know but useless :)
 
Dsg319 said:
If I understand your question correctly you could only add an additional 10awg of the same size with the fraction of 0.8 or greater.
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But unless they are all the same size how do you know which one of the sizes you can round up?

If you have all 14 and 12, maybe not too big of a deal to add one or the other. If you have 3/0 and 4 AWG conductors in the raceway, adding one more 3/0 makes a bigger difference than adding one more 4 AWG.

When it is all same size and you come up with say 5.8 conductors is max fill, if you round that up to 6 the amount of "overfill" is pretty minimal, especially when dealing with a 40% fill being maximum in the first place other than one and two conductor applications.
 
augie47 said:
If they are all the same size you are likely to use Table C which takes the .8 factor into consideration so it's kinda one of those nice thing s to know but useless :)
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Hey I worked hard on that table and it was a pain getting that .8 to work. I believe I started a thread on that and got help on that issue from Smart $... Now I feel useless...
 
Dennis Alwon said:
Hey I worked hard on that table and it was a pain getting that .8 to work. I believe I started a thread on that and got help on that issue from Smart $... Now I feel useless...
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Those tables are partially your fault? IMO all they do is add more pages to the book, I hardly have ever used them.

Anyone that runs enough raceway knows how many 14, 12 and 10 fit in most 1/2 and 3/4 raceways off top of their head anyway and maybe a few other common conductor and raceway applications are stuck in their head as well. If anything varies from those usual applications, go to chapter 9 and figure it out. If not all same size you are using chapter 9 regardless.
 
kwired said:
Those tables are partially your fault? IMO all they do is add more pages to the book, I hardly have ever used them.

Anyone that runs enough raceway knows how many 14, 12 and 10 fit in most 1/2 and 3/4 raceways off top of their head anyway and maybe a few other common conductor and raceway applications are stuck in their head as well. If anything varies from those usual applications, go to chapter 9 and figure it out. If not all same size you are using chapter 9 regardless.
Click to expand...


Thanks, I appreciate the helpful and atta boy compliments. Not everyone is as vain and as smart as you.
 
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