40% conduit fill

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calisparky6

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i want to install in 3/4 EMT 3#6 THHN with 2#10 THHN with a #10 ground. my calculations show that conduit fill at 40% code book shows .213 sq/in and my fill comes in at .215. im not compliant right...and i should install 1".
 
Smart $

Smart $

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Possibly.

As noted in the NEC tables, size is approximate. Check with manufacturer of wire for nominal size. For example, Southwire's simpull thhn nominal OD sizes are #6 at .249" and #10 at .161. The Chapter 9 tables put these sizes at .254 and .164 respectively. The difference would make your impending installation compliant.
 
don_resqcapt19

don_resqcapt19

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Smart $ said:
Possibly.

As noted in the NEC tables, size is approximate. Check with manufacturer of wire for nominal size. For example, Southwire's simpull thhn nominal OD sizes are #6 at .249" and #10 at .161. The Chapter 9 tables put these sizes at .254 and .164 respectively. The difference would make your impending installation compliant.
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i don't see where the code permits us to use the actual dimensions for single conductors. In the Chapter 9 Notes to the Tables, Note 6 requires us to use the dimensions in Tables 5 and 5A for wire fill calculations involving multiple sizes of single conductors.

If all of the conductors were of the same size, Note 7 would permit this installation, but Note 7 does not apply to differing sizes of conductors. I would be tempted to ask the AHJ to permit me to use a modification of Note 7. I would ask him to let me subtract the area of the 3 #10s and then let me apply Note 7 to the #6s using the remaining area after the area for the 10s is taken out. The resulting decimal number of #6s permitted is 2.95. If the AHJ would permit this modified use of Note 7, I could round the 2.95 up to 3.
 
Smart $

Smart $

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don_resqcapt19 said:
i don't see where the code permits us to use the actual dimensions for single conductors. In the Chapter 9 Notes to the Tables, Note 6 requires us to use the dimensions in Tables 5 and 5A for wire fill calculations involving multiple sizes of single conductors.
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Darn... forgot about that.

An easy solution would be to pull a bare #10 EGC.
 
iwire

iwire

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calisparky6 said:
i want to install in 3/4 EMT 3#6 THHN with 2#10 THHN with a #10 ground. my calculations show that conduit fill at 40% code book shows .213 sq/in and my fill comes in at .215. im not compliant right...and i should install 1".
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3 - 6 AWG and 3 10 AWGs?

Code aside you need to get the conductors installed in the conduit, unless this is a short run with few bends, no LBs etc. my experience says that is going to be a tough pull in 3/4".

Derating comes to mind as well.
 
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poeboy

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iwire said:
3 - 6 AWG and 3 10 AWGs?
. my experience says that is going to be a tough pull in 3/4".

Derating comes to mind as well.
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I agree it is going to be a tough pull, unless it is darn near a straight, very short run..... How long is the run ??

Derating would be my bigger concern as well....Chances are good the #10's are OK, but what are you planning to fuse the #6's at??

Along the same lines as derating, are they continuous or intermittent loads on the conductors??
 
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Dennis Alwon

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You are using EMT so you do not need a ground wire unless it is speced or the equipment calls for it. Eliminating the ground wire, if possible, should make it nice and cozy.
 
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calisparky6

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the install is for a hot tub and a pool pump. i cant run a bare ground because its considered a "feeder" because i'm feeding the spa disconnect gfci. its pretty straight and ill use soap of course. but itll be way harder to bend 1". 3/4 if its code and the inspector won't ding me...thats what i want to know. ill chance it i think.
 
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calisparky6

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nope. it's a four wire 40a pump. it calls for #8 but because the run is over 100'...i went with #6. the #10 is for a 14a pump for pool. i'm going to run the #6 to a gfci 50a disconnect that also has space for a convenice receptacle. the #10 i run to a disconnect (breaker at main panel will be 20a gfi) and then to the twist lock receptacle to feed pool.

i'm an apprentice who has picked up some side jobs to help out my buddies (and pay for summer vacation). i thought this hot tub was a no brainer..but its turned out to be more complicated than i thought. my 2008 code book has been constantly opened. i'm learning a lot though. and this forum is great. thanks guys.

also the code is contradictory..in one case it calls for disconnecting means to be no more than 5' and then in another section it calls for disconnecting means to be no less than 5'?
 
Dennis Alwon

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Sparky shouldn't you be licensed to do this work? Also have you put down an equipotential bonding around the tub???
 
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Smart $

Smart $

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calisparky6 said:
... it calls for #8 but because the run is over 100'...i went with #6. ...
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If your OCPD is 50A and you're upsizing the ungrounded conductors from #8 to #6 for voltage drop, you must also upsize the EGC from #10 to #8 [250.122(B)]

also the code is contradictory..in one case it calls for disconnecting means to be no more than 5' and then in another section it calls for disconnecting means to be no less than 5'?
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Please cite a code reference so we know what requirements you are discussing. Offhand I know of no rules stating such... but pools and spas are not my forte.
 
Dennis Alwon

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Smart the OP is confusing the disco with the emergency Off switch for other than single family dwellings.

680.41 Emergency Switch for Spas and Hot Tubs.
A clearly labeled emergency shutoff or control switch for the purpose of stopping the motor(s) that provide power to the recirculation system and jet system shall be installed at a point readily accessible to the users and not less than 1.5 m (5 ft) away, adjacent to, and within sight of the spa or hot tub. This requirement shall not apply to single-family dwellings.
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Smart $

Smart $

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Dennis Alwon said:
Smart-- what are you saying is news to you. The fact that it's a feeder or that a bare conductor cannot be run.
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I'm not saying a bare EGC cannot be run.... cali' is. I'm the one that suggested running a bare EGC to begin with. If running a bare EGC is not permitted for run in conduit, please cite a reference... especially regarding a feeder for this case.
 
Dennis Alwon

Dennis Alwon

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Smart $ said:
I'm not saying a bare EGC cannot be run.... cali' is. I'm the one that suggested running a bare EGC to begin with. If running a bare EGC is not permitted for run in conduit, please cite a reference... especially regarding a feeder for this case.
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If this is a feeder art. 680.25(B) clearly states an insulated ground.

680.25(B) Grounding. An equipment grounding conductor shall be installed with the feeder conductors between the grounding terminal of the pool equipment panelboard and the grounding terminal of the applicable service equipment or source of a separately derived system. For other than (1) existing feeders covered in 680.25(A), Exception, or (2) feeders to separate buildings that do not utilize an insulated equipment grounding conductor in accordance with 680.25(B)(2), this equipment grounding conductor shall be insulated.
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