Junction box sizing?

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ritelec

ritelec

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Jersey
It's been a while and I forgot. How do I size a junction box.
Not for pulls, but for conductor fill of 4awg and larger.

I'm basically going to be splicing two 4-3 ser cables and will do it in a 6" box but I'd like to know the correct calculation again.

Box cubed.
Table 5 = inches squared?
312.8 ?? 75% ? (although it doesn't seem like a cross section. I would think cross section would be in a through or panel gutter, ?? wasn't that 20%)

Thank you.
 
Know the size of the conduit that enters the box. For straight pulls, you multiply the conduit diameter by 8 to get the width of the face where the conduit enters. For bent pulls, you multiply the largest conduit entering that face by 6 and add the diameters of other conduits along that row with the largest conduit --> to get that side of the box's width.
Just my 2 cents!
 
Still trying to get this. If I do the calculation for a two 6-3 nm into a box, as per 314.16A I can splice it in a deep 4 11/16 box.
I believe that 6-3 in a conduit would need to be a 2" conduit. So I would be looking at a 12" box for two 6-3nm's in 2 - conduits.
Something's not right.
 
4-3 ser in conduit (although it's not going to be in conduit) would probably turn into a 18" box.
Somethings not right.
 
ritelec said:
Still trying to get this. If I do the calculation for a two 6-3 nm into a box, as per 314.16A I can splice it in a deep 4 11/16 box.
I believe that 6-3 in a conduit would need to be a 2" conduit. So I would be looking at a 12" box for two 6-3nm's in 2 - conduits.
Something's not right.
Click to expand...
What's not right is that #6 AWG uses the cubic inch calculation not the 6X and 8X calculation.
 
ritelec said:
Still trying to get this. If I do the calculation for a two 6-3 nm into a box, as per 314.16A I can splice it in a deep 4 11/16 box.
I believe that 6-3 in a conduit would need to be a 2" conduit. So I would be looking at a 12" box for two 6-3nm's in 2 - conduits.
Something's not right.
Click to expand...
It isn't the cable in the conduit, it is the equivalent of the conductors in conduit. So 3#4 and 1 #8 fit in a 1" EMT. box size 6" if entering one side an adjacent side. 8 times for the same conductors exiting the opposite end, but since you are splicing, they aren't the same conductors, so also 6 times. Code is 314.28
 
Strathead said:
It isn't the cable in the conduit, it is the equivalent of the conductors in conduit. So 3#4 and 1 #8 fit in a 1" EMT. box size 6" if entering one side an adjacent side. 8 times for the same conductors exiting the opposite end, but since you are splicing, they aren't the same conductors, so also 6 times. Code is 314.28
Click to expand...
From what I see. You’re talking single conductors in a conduit
for NM
3 #4s and 1 #8 is not correct in a 1 “ emt

From some math I did on a paper way back that is in my book
14-2= 1/2. 12-2= 3/4. 8-2=1 6-2=1.25
14-3= 3/4. 12and10-3=1. 8-3=1.5
6-3=2
Haven’t done the math yet for 4-3 but it will have to be at least 2”

So would you be saying that size the conduit as single conductors per conductor or fixture wire in conduit and NOT as a cable in conduit?
 
electrofelon said:
You will have to transpose the cable size to the min equivalent raceway size. Don't forget those conductors will be compact (assuming AL). The southwire calculator does compact conductors.
Click to expand...
Respectfully Electrofelon
Your saying don’t do this, treating them as a cable for sizing the conduit. Size conduit as if they were single conductors. Correct? That would make more sense.
 
ritelec said:
Still trying to get this. If I do the calculation for a two 6-3 nm into a box, as per 314.16A I can splice it in a deep 4 11/16 box.
I believe that 6-3 in a conduit would need to be a 2" conduit. So I would be looking at a 12" box for two 6-3nm's in 2 - conduits.
Something's not right.
Click to expand...


First you said 4/3 now you are saying 6/3. Also 6/3 would fit in a conduit smaller than 2" for sure.

Also I would think you would size the raceway based on the wires themselves not the cable.
 
ritelec said:
From what I see. You’re talking single conductors in a conduit
for NM
3 #4s and 1 #8 is not correct in a 1 “ emt

From some math I did on a paper way back that is in my book
14-2= 1/2. 12-2= 3/4. 8-2=1 6-2=1.25
14-3= 3/4. 12and10-3=1. 8-3=1.5
6-3=2
Haven’t done the math yet for 4-3 but it will have to be at least 2”

So would you be saying that size the conduit as single conductors per conductor or fixture wire in conduit and NOT as a cable in conduit?
Click to expand...
That is just what I said. Here is the code wording:

When transposing cable size into raceway size in
314.28(A)(1) and (A)(2), the minimum metric designator
(trade size) raceway required for the number and size of
conductors in the cable shall be used.
 
ritelec said:
Respectfully Electrofelon
Your saying don’t do this, treating them as a cable for sizing the conduit. Size conduit as if they were single conductors. Correct? That would make more sense.
Click to expand...
Treat the conductors in the cable as if they were individual conductors in conduit, and find the minimum raceway size. Presumably EMT will give you the most fill.
 
wwhitney said:
I was just checking that, because of this thread. IMC has a bigger area that EMT (at least in the 1" size I was looking at), and PVC Type A was even bigger. Whatever PVC Type A is.

Cheers, Wayne
Click to expand...
Hmmm ok....EMT sizes 3" and larger are same OD as rigid, but under 3" I do know the sizes are different and wacky but I just assumed it would still provide more fill than rigid or schedule 40
 
electrofelon said:
Hmmm ok....EMT sizes 3" and larger are same OD as rigid, but under 3" I do know the sizes are different and wacky but I just assumed it would still provide more fill than rigid or schedule 40
Click to expand...
Per the Chapter 9 tables, for EMT vs IMC, IMC has a bigger ID through 2", EMT is bigger for 2-1/2" and up.

For PVC Type A, it's always bigger than IMC, but EMT is again bigger than it for 2-1/2" and up.

Cheers, Wayne
 
Dennis Alwon said:
First you said 4/3 now you are saying 6/3. Also 6/3 would fit in a conduit smaller than 2" for sure.

Also I would think you would size the raceway based on the wires themselves not the cable.
Click to expand...
Yes. I will be working with number four, I was just referencing the 6’s because I had done the math for them as a cable in a conduit. Yes the 6’s will fit in a smaller conduit but from what I can tell it doesn’t meet code. Like 12-2 will fit in a 1/2 but math says 3/4.

I did the math to find out what size conduit was required for nm a few years ago then re did it again last year.

I could look for my notes how to achieve the conduit size again but for now I just have the results on a piece of paper in my book.

So I will size the box as if the #4’s were in a conduit.

thank you.
 
ritelec said:
Yes. I will be working with number four, I was just referencing the 6’s because I had done the math for them as a cable in a conduit. Yes the 6’s will fit in a smaller conduit but from what I can tell it doesn’t meet code. Like 12-2 will fit in a 1/2 but math says 3/4.

I did the math to find out what size conduit was required for nm a few years ago then re did it again last year.

I could look for my notes how to achieve the conduit size again but for now I just have the results on a piece of paper in my book.

So I will size the box as if the #4’s were in a conduit.

thank you.
Click to expand...
Exactly what the code requires.
 
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