more then 3 CCC and larger conduit

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mjmike

Senior Member
If conductors are derated due to more than 3 CCC's in the same conduit, can the conduit be upsized to counteract the derating? Conductors are derated because of heat so you would think a larger conduit would dissipate this. Thanks.
 
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winnie

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Springfield, MA, USA
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Electric motor research
The long answer is that code rules require derating for more than 3 CCC, and offer no credit for using any sort of oversized conduit.

I certainly agree that the _physics_ of the situation would allow a larger conduit to dissipate more heat and thus avoid the need for derating, but code is intentionally meant to be simplified with _lots_ of wiggle room. If you actually went and determined the heat dissipation capacity for _most_ installations, the _true_ ampacity of the conductors would be much greater than code allows.

If you wanted to spend money on calculations and engineering supervision, then you could use 310.15(C), and avoid being stuck with mandatory derating. Might even be worth it in some situations with expensive conductors and large conduits.

-Jon
 
charlie b

charlie b

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iwire said:
I think you are forgetting how many engineers we have here.:p
Click to expand...
OK. Let me start by giving you the derivation of the word, "temperature." It comes from the Latin word, "temperatura," which means "a tempering." When applied to the conditions inside a conduit . . . .

Oh, sorry, I have to run to a meeting. I will have to finish this explanation later. :lol:

 
qcroanoke

qcroanoke

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Sorta retired........
mjmike said:
If conductors are derated due to more than 3 CCC's in the same conduit, can the conduit be upsized to counteract the derating? Conductors are derated because of heat so you would think a larger conduit would dissipate this. Thanks.
Click to expand...

I once rejected an install of 2-1/2 EMT with 10 #12's in it because of the de-rate.
Electrician (who was a good friend" told me daggone Mike, I can run a full grown groundhog through there and you're telling me I have to run another raceway or pull larger conductors? ;)
 
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fmtjfw

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Location
Fairmont, WV, USA
Can some one tell me how having larger conduit means the wires will be cooler? Once you get to the point that all the wires are resting on the conduit that is?
 
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GoldDigger

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Placerville, CA, USA
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Retired PV System Designer
With more surface area, the conduit wall and the air inside the conduit will be cooler given identical heat input.
How much of a difference that actually makes would require calculations, and its Friday.

Tapatalk!
 
roger

roger

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Fl
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fmtjfw said:
Can some one tell me how having larger conduit means the wires will be cooler? Once you get to the point that all the wires are resting on the conduit that is?
Click to expand...
I think Gus once pointed out a bigger oven with a small element my take longer to come to heat but eventually it will.

Roger
 
iwire

iwire

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Massachusetts
Just run some finned EMT.

1097476_ltype.gif
 
Ponchik

Ponchik

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Location
CA
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Electronologist
Hypothetically speaking,

If you have 15 conductors and you could somehow float the conductors in the raceway, so they are not resting on top of each other, do you still have to derate? :):)
 
Besoeker

Besoeker

Senior Member
Location
UK
edward said:
Hypothetically speaking,

If you have 15 conductors and you could somehow float the conductors in the raceway, so they are not resting on top of each other, do you still have to derate? :):)
Click to expand...
The heat generated still has to get out of the conduit via its surface.
 
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