conduit fill

[Dare]

IF i do 2'' emt conduit what will be the most amount of # 12 wires to pull in it.All circuits will be for lighting loads.Also size same conduit for power and motor loads, this conduit will contain different wire sizes.So i would have two separate runs both 2'' emt one only lighting loads and other mixed power and motor loads How and what table do i use .Table 310.15(B) 2 a,Annex c ??????.Will someone please help me understand this .THANKS

 

[Ponchik]

IF i do 2'' emt conduit what will be the most amount of # 12 wires to pull in it All circuits will be for lighting loads.Also size same conduit for power and motor loads, this conduit will contain different wire sizes.So i would have two separate runs both 2'' emt one only lighting loads and other mixed power and motor loads How and what table do i use .Table 310.15(B) 2 a,Annex c ??????.Will someone please help me understand this .THANKS

Annex C table C1. you also need to know what kind of conductor insulation you have

First you need to know what size conductors are being installed for those particular circuits, then you start on Ch 9 table 1, then table 5 and at last table 4.


If you are doing the whole calculation (conductor sizing, conduit sizing...) you also need to consider conduit fill adjustment factor 310.15(b)(2)(a), 310.15(b)(2)(c) and temperature correction factor of table 310.16

 

[Dare]

In first conduit all conductors are THHN rated insulation and they are 20 amps.So first i have to find approx area of one conductor table 5, than in2 for 2'' conduit table 4 and number you get is the same number we have in table C 1.Please correct me I don't understand whole process.
Also when and how you apply adjustment factors

 

[DARUSA]

In first conduit all conductors are THHN rated insulation and they are 20 amps.So first i have to find approx area of one conductor table 5, than in2 for 2'' conduit table 4 and number you get is the same number we have in table C 1.Please correct me I don't understand whole process.
Also when and how you apply adjustment factors

Adjustment factor have nothing to do with conduit fill calculations!!!

 

[david luchini]

In first conduit all conductors are THHN rated insulation and they are 20 amps.So first i have to find approx area of one conductor table 5, than in2 for 2'' conduit table 4 and number you get is the same number we have in table C 1.Please correct me I don't understand whole process.

Yes, that is correct. Table 4 gives the allowable fill for 2"emt as 1.342 sq. in. Table 5 gives you the area of #12 THHN as 0.0133 sq. in. So, 1.342/0.0133 = 100.9 #12 THHN will fit in a 2" emt. (Annex C lists 101 conductors allowed.)

Also when and how you apply adjustment factors

You must apply adjustment factors whenever you have more than 3 current carrying conductors in a raceway - See 310.15(B)(2)(a).

If you had 100 current carrying conductors, #12 THHN, in the same conduit, the ampacity of the conductors would be 10.5. That means the max load on each circuit could only be 10.5 Amps, and you would need to protect the circuits with a 15A c/b rather than a 20A c/b.