Junction box sizing?

[ritelec]

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.

 

[infinity]

You do not use the cubic inch method (that ends at #6 AWG) you use the 6X or 8X method.

 

[topgone]

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!

 

[ritelec]

You do not use the cubic inch method (that ends at #6 AWG) you use the 6X or 8X method.

it's 6x a 3/4 or 1" ser connector. I'm terminating two ser cables.

 

[electrofelon]

it's 6x a 3/4 or 1" ser connector. I'm terminating two ser cables.

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.

 

[ritelec]

Act and calculate the size of the box "as if" I was installing those cables in conduit?

 

[ritelec]

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.

 

[ritelec]

4-3 ser in conduit (although it's not going to be in conduit) would probably turn into a 18" box.
Somethings not right.

 

[infinity]

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.

What's not right is that #6 AWG uses the cubic inch calculation not the 6X and 8X calculation.

 

[Strathead]

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.

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

 

[ritelec]

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

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?

 

[ritelec]

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.

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.

 

[Dennis Alwon]

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.

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.

 

[Strathead]

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?

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.

 

[electrofelon]

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.

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]

Presumably EMT will give you the most fill.

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

 

[electrofelon]

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

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

 

[wwhitney]

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

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

 

[ritelec]

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.

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.

 

[don_resqcapt19]

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.

Exactly what the code requires.