Sizing junction box.

[Mr. M]

Good evening gentlemen.

I'm trying to determine the correct size junction box for 8 #2- THWN AL conductors, and 6 #12 THWN conductors.

I'll be splicing a 2/3 SER cable to the to the to 4 conductors entering from a 2 inch PVC entering from another location, and splicing

the incoming the 6 # 12's as well.

Thanks

 

[augie47]

Have you looked at 314.28 ?
More specifics about entry points would be needed to determine the exact size.

 

[JDB3]

Article 314.

 

[Mr. M]

J box sizing

J box sizing

I did look at 314-28. Didn't seem to help. I'll try to simplify.

At one location the following conductors are a 2/3 SER AL cable, and 2- 14/3 NMC conductors . The 2/3 will have 1 1/4 connector, and 2- 1/2 connectors for the romex.

I'll splice incoming 4- #2's and 6- #14 THWN that are entering from a 2 " conduit at the adjoining location. What size box will I need?

Hope I clarified.

Thanks

 

[GoldDigger]

I did look at 314-28. Didn't seem to help. I'll try to simplify.

At one location the following conductors are a 2/3 SER AL cable, and 2- 14/3 NMC conductors . The 2/3 will have 1 1/4 connector, and 2- 1/2 connectors for the romex.

I'll splice incoming 4- #2's and 6- #14 THWN that are entering from a 2 " conduit at the adjoining location. What size box will I need?

Hope I clarified.

Thanks

1. In addition to the box fill limits, the bending space for the wires will depend on exactly which sides of the box the different conduits and NM clamps are entering from.
2. Will you be pulling any conductors through the box or will they all be terminated (spliced) there?

 

[Little Bill]

1. In addition to the box fill limits, the bending space for the wires will depend on exactly which sides of the box the different conduits and NM clamps are entering from.
2. Will you be pulling any conductors through the box or will they all be terminated (spliced) there?

How would you determine anything about the box if some of the conductors are entering via a cable clamp?
Since the code book is talking about conduit size entering.
I never thought of that scenario before.

 

[mjf]

How would you determine anything about the box if some of the conductors are entering via a cable clamp?
Since the code book is talking about conduit size entering.
I never thought of that scenario before.

Oh no, now the code book will be even LOOOOONGER!!!

 

[Little Bill]

Oh no, now the code book will be even LOOOOONGER!!!

The code makers should have to have restrictions on our "mind bending" radius!

 

[infinity]

Cable clamp or conduit entry the rules are the same:

314.28(A) Minimum Size. For raceways containing conductors
of 4 AWG or larger that are required to be insulated, and for
cables containing conductors of 4 AWG or larger, the mini-
mum dimensions of pull or junction boxes installed in a
raceway or cable run shall comply with (A)(1) through
(A)(3). Where an enclosure dimension is to be calculated
based on the diameter of entering raceways, the diameter
shall be the metric designator (trade size) expressed in the
units of measurement employed.

 

[augie47]

Keep in mind, boxes for #4 and larger conductors are based on conduit size not cubic inches. Your 2" conduit would require a box 6 X the diameter for the opposite wall, so one dimension would be 12", #3's as indivual conductors would most likely fit a 1-1/4 conduit (based on Tables) so that dimmension would be 7-1/2". Under certain conditions you might have to consider the 14s but from a practical standpoint they make little difference.
IMO, your j box would need to be 12 x 8

 

[Mr. M]

Keep in mind, boxes for #4 and larger conductors are based on conduit size not cubic inches. Your 2" conduit would require a box 6 X the diameter for the opposite wall, so one dimension would be 12", #3's as indivual conductors would most likely fit a 1-1/4 conduit (based on Tables) so that dimmension would be 7-1/2". Under certain conditions you might have to consider the 14s but from a practical standpoint they make little difference.
IMO, your j box would need to be 12 x 8

Thanks Augie47

I calculated the same 6x2, plus 6x 1 1/4. 12x8.

 

[Mr. M]

Keep in mind, boxes for #4 and larger conductors are based on conduit size not cubic inches. Your 2" conduit would require a box 6 X the diameter for the opposite wall, so one dimension would be 12", #3's as indivual conductors would most likely fit a 1-1/4 conduit (based on Tables) so that dimmension would be 7-1/2". Under certain conditions you might have to consider the 14s but from a practical standpoint they make little difference.
IMO, your j box would need to be 12 x 8

Thanks Augie47

I calculated the same 6x2, plus 6x 1 1/4. 12x8.

 

[kwired]

How would you determine anything about the box if some of the conductors are entering via a cable clamp?
Since the code book is talking about conduit size entering.
I never thought of that scenario before.

Last sentence in 314.28(A)(2):"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."