I have (4) 4" PVC conduits stubbing up into a Christy box and back out, making it a total of (8) 4" conduits, to be utilized as a pull point. They enter the bottom of the box and make a U-bend and exit the bottom (same wall)(250kcmil conductors). I know I can take the exception 314.28(A)(2) but what about the Width x Length? Conduits configuration will be 1 row of 4 conduits which means the distance between the 2 rows will need to be 36"? 4" x 6 = 24" + 4" + 4" + 4" = 36". Does that mean the distance between conduits need to be 36" or the Christy box need to be at least 36" in length? What about width? Thanks for any help you guys can provide!
CHRISTY BOX SIZING FOR U-PULL?
- Thread starter CP3
- Start date
- Location
- Illinois
- Occupation
- retired electrician
Two rows 24" apart. Assuming you need 6" per entry, that would be 24x36
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
Don gave a simple answer. Here's an excessively detailed answer that agrees:
314.30 covers handhole enclosures and tells us when applying 314.28(A) to treat the ends of the raceways as the "bottom" of the open bottom box.
As to 314.28(A), if you are splicing your conductors within the handhole enclosure, then the only regulated dimension is the depth of the box, the distance from the end of the conduit to the removeable cover, as per 314.28(A) Exception. The width and the length can be whatever you like that is sufficient for all the conduits and to provide enough space to work in and make up the splices.
If instead you are pulling conductors through the box without splicing, then your width and length will be determined by the requirement that "The distance between raceway entries enclosing the same conductor shall not be less than six times the metric designator (trade size) of the larger raceway." So each pair of 4" conduits containing the same conductors will need to be 24" apart (I assume that's a clear dimension, rather than center-to-center.)
For example, the obvious layout to use is a row of 4 conduits coming in on one side and a row of 4 conduits going out on the other side. If you want each 4" conduit to be say 1" away from the interior sides of the enclosure, and 1" away from others in the row, then each row would take up 4*4.5 + 5 * 1 = 23" of internal space, so you'd want one internal dimension to be at least 23". If each wire goes from a conduit straight across to the corresponding conduit in the other row, then the distance between rows would be need to be 24", and this internal dimension would need to be at least 2*1 + 2*4.5 + 24 = 35".
If you want to make it smaller, then one simple variation on the above would be to run the wires diagonally across the box instead of straight across. Each conduit in one row would have wires going into the conduit 2 up or down in the other row. That would give you 11" of offset between conduits containing the same conductors, so the space between rows would only need to be sqrt(242-112) = 21.33". So you could save 2.5" and get away with 23" x 32.5" interior dimensions. Of course, having the conductors cross over like that might be more trouble than it is worth.
Cheers, Wayne
314.30 covers handhole enclosures and tells us when applying 314.28(A) to treat the ends of the raceways as the "bottom" of the open bottom box.
As to 314.28(A), if you are splicing your conductors within the handhole enclosure, then the only regulated dimension is the depth of the box, the distance from the end of the conduit to the removeable cover, as per 314.28(A) Exception. The width and the length can be whatever you like that is sufficient for all the conduits and to provide enough space to work in and make up the splices.
If instead you are pulling conductors through the box without splicing, then your width and length will be determined by the requirement that "The distance between raceway entries enclosing the same conductor shall not be less than six times the metric designator (trade size) of the larger raceway." So each pair of 4" conduits containing the same conductors will need to be 24" apart (I assume that's a clear dimension, rather than center-to-center.)
For example, the obvious layout to use is a row of 4 conduits coming in on one side and a row of 4 conduits going out on the other side. If you want each 4" conduit to be say 1" away from the interior sides of the enclosure, and 1" away from others in the row, then each row would take up 4*4.5 + 5 * 1 = 23" of internal space, so you'd want one internal dimension to be at least 23". If each wire goes from a conduit straight across to the corresponding conduit in the other row, then the distance between rows would be need to be 24", and this internal dimension would need to be at least 2*1 + 2*4.5 + 24 = 35".
If you want to make it smaller, then one simple variation on the above would be to run the wires diagonally across the box instead of straight across. Each conduit in one row would have wires going into the conduit 2 up or down in the other row. That would give you 11" of offset between conduits containing the same conductors, so the space between rows would only need to be sqrt(242-112) = 21.33". So you could save 2.5" and get away with 23" x 32.5" interior dimensions. Of course, having the conductors cross over like that might be more trouble than it is worth.
Cheers, Wayne
Thank you very much Wayne for the detailed break down, I really appreciate it!
Thank you Don!
"Where splices or where angle or U pulls are made, the distance between each raceway entry inside the box or conduit body and the opposite wall of the box or conduit body shall not be less than six times the metric designator (trade size) of the largest raceway in a row. This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries in the same row on the same wall of the box. Each row shall be calculated individually, and the single row that provides the maximum distance shall be used." In my prior example of 1 row of (4) 4" conduits, would this sentence after mean I would actually be needing a minimum distance of 36" to account for the additional entries in the same row?
"Where splices or where angle or U pulls are made, the distance between each raceway entry inside the box or conduit body and the opposite wall of the box or conduit body shall not be less than six times the metric designator (trade size) of the largest raceway in a row. This distance shall be increased for additional entries by the amount of the sum of the diameters of all other raceway entries in the same row on the same wall of the box. Each row shall be calculated individually, and the single row that provides the maximum distance shall be used." In my prior example of 1 row of (4) 4" conduits, would this sentence after mean I would actually be needing a minimum distance of 36" to account for the additional entries in the same row?
wwhitney
Senior Member
- Location
- Berkeley, CA
- Occupation
- Retired
That sentence is referring to the minimum distance between the entry and the opposite wall, which would be your depth, not your length or width.
But as your opposite wall is a removable cover, you can use the exception, which has no such language. All you need to provide for depth is the wire bending space from Table 312.6(A), which is 4" or 4-1/2" depending on whether the conductors are compact stranded aluminum or not. So your depth, from the top of the conduits to the bottom of the removeable cover, needs to be at least 4" or 4-1/2"; I imagine it may be prudent to provide a bit more depth than that but have no applicable hands on experience.
Cheers, Wayne