half inch condit

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steelerdude said:
What is the max amperage for a half inch (emt) conduit? You can get 3 # 12's so is the answer 20?


thank you
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The ampacity of a 12 AWG THHN is 30, but limited to 25 amps at 75 deg C. For motors it would not be unusual to see a 50 amp CB with 12 AWG.
Its a poor question
 
jusme123 said:
....length was not given, what % fill are you basing your reply on?
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What does length have to do with this or the price of peanut butter? ;)The fill is based on 31% that has been discussed already. See the notes to tables in chapter 9 and Annex C for more.

Roger
 
jusme123 said:
the origonal question was looking for the max. amperage for 1/2" conduit. Is the OP asking for wire size or OCPD?
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1/2 inch conduit is not normally intended to carry current except for situations allowing it to be used as an equipment grounding conductor. How many amps worth of conductors you can place within it ... usually this is not something calculated either. You would normally figure out what you have for load first, then figure out what you would need for conductors to supply it, then determine what size of conduit is needed to contain them. - But maybe I have not been doing it right for a long time now.

roger said:
What does length have to do with this or the price of peanut butter? ;)The fill is based on 31% that has been discussed already. See the notes to tables in chapter 9 and Annex C for more.

Roger
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If length is less than 24 inches it changes fill requirements.
 
Dennis Alwon said:
I would not use annex C as it is full of inaccuracies. I am not even sure why it is there as it is not an NFPA document.
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outside of 14,12,&10 AWG in 1/2-3/4 and maybe 1 inch raceways...how often do you have all same size conductors in a raceway? your EGC is usually smaller and maybe the neutral is smaller sometimes. Besides I can calculate maximum fill faster with Ch9 than I can find right table in annex C Helps when you have area of 14-6AWG already memorized because you use them enough you don't need to look them up.
 
K8MHZ said:
You are on the right track. Two conductors take up more space per conductor than any other number in a round pipe.
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I am an NPIT* and I was taught details are important so I will point out that three conductors take up more 'space' than two conductors assuming all conductors are the same size.

space
   [speys] Show IPA noun, verb, spaced, spac?ing, adjective
noun
1.
the unlimited or incalculably great three-dimensional realm or expanse in which all material objects are located and all events occur.
2.
the portion or extent of this in a given instance; extent or room in three dimensions: the space occupied by a body.
3.
extent or area in two dimensions; a particular extent of surface: to fill out blank spaces in a document.
4.
Fine Arts .
a.
the designed and structured surface of a picture: In Mondrian's later work he organized space in highly complex rhythms.
b.
the illusion of depth on a two-dimensional surface.
5.
outer space.
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Now before you go one about how three bundle better than two, I agree, but even when bundled nicely the total space used is greater ......... details ...... details ........










(*Nit Picker In Training :angel: :D)
 
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The only thing I can think of is that in certain situations when 2 wires are installed there is dead space under where the 2 wires may lay on the bottom side by side. This would make the pulling area smaller but does not change the free space in the conduit.
 
iwire said:
I am an NPIT* and I was taught details are important so I will point out that three conductors take up more 'space' than two conductors assuming all conductors are the same size.





Now before you go one about how three bundle better than two, I agree, but even when bundled nicely the total space used is greater ......... details ...... details ........










(*Nit Picker In Training :angel: :D)
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Geez.....do I have to draw a picture for you? :p
 
Amount of extra area needed in tubing per number of conductors (for 100% fill):

1 conductor = 1 unit and can fit in a 1 unit tube. 0 units of extra area per conductor is needed.

2 conductors = 2 units but need a 3.14 unit tube. 0.57 units of extra area is needed per conductor.

3 conductors = 3 units and will fit in a 3.5325 unit tube. 0.1775 units of extra area is needed per conductor.

4 conductors = 4 units and will fit in a 4.71 unit tube. 0.1775 units of extra area is needed per conductor.

and so on, gradually decreasing from 0.1775 per unit as the number of conductors increase.
 
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Here is how fill works out

Each large circle is 1 inch diameter. Each one in top row has smaller circles with max 53, 31, or 40% fill inside.

The bottom one has three of the same size as the 2 @31% inside it.

racewayfill.jpg


Judge for yourself if three @ 40% is more than 2 @ 31%
 
iwire said:
I am an NPIT* and I was taught details are important so I will point out that three conductors take up more 'space' than two conductors assuming all conductors are the same size.





Now before you go one about how three bundle better than two, I agree, but even when bundled nicely the total space used is greater ......... details ...... details ........










(*Nit Picker In Training :angel: :D)
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Glad you cleared that up! I was thinking "Natural Pain in the ^**!:D
 
kwired said:
Here is how fill works out

...
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Your fill is off. Look at the one small circle in large circle. You can fit about six more smaller circles around the existing one. The one circle is far from 53% of the larger. At 53%, the smaller circle should have a diameter 73% of the larger. What you have for diameter is more likely the radius.
 
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