310.60

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Shockedby277v

Shockedby277v

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Michigan
I got hit on this with my underground service feeders. We have always ran our feeders tight together, this is the first I have come into this. This being my first job as a job runner, I was in awe when he said I was bundling my pipes and running them in that trench is concidered a duct bank. He pointed out the article to me in the code book and offered a remedy he would except. Do any of you guys always watch your spacing when doing your underground? Another question I failed to ask was, does my branch circuit pipes also need to have spacing??
 
I do not believe there is generally any need for special spacing of conduits in free air. The reason for requiring spacing underground is because earth is not an especially good conductor of heat.
 
This brings up the question that I have yet to get an answer to is how far apart does a conduit or cable need to be to not be "bundled"? If it is not tuching the others is this far enough or does it need to be a specified distance based on what?
 
I know that the buried conduits and cables need a minimum spacing, what I am unsure of is the spacing of conduits in a wall or ceiling , the same for NM cables. We are told to derate if bundled for more then 24", how far apart is far enough to not have to derate?
 
acrwc10 said:
I know that the buried conduits and cables need a minimum spacing, what I am unsure of is the spacing of conduits in a wall or ceiling , the same for NM cables. We are told to derate if bundled for more then 24", how far apart is far enough to not have to derate?
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Check out 310.15(B)2b
(b) More Than One Conduit, Tube, or Raceway. Spacing between conduits, tubing, or raceways shall be maintained.

Spacing is normally maintained between individual conduits in groups of conduit runs from junction box to junction box because of the need to separate the conduits where they enter the junction box, to allow room for locknuts and bushings. Field experience has indicated that this degree of spacing between runs has not caused any problems.
Rick
 
acrwc10 said:
. . . how far apart does a conduit or cable need to be to not be "bundled"?
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Shockedby277v said:
7 1/2" center to center apart . Look at table 310.60.
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Not true, IMHO. The 7.5 inches is not a minimum requirement, nor is it a sufficient condition to establish the cables as not being ?bundled.? This is a common misconception. That spacing does appear in many figures in the NEC, but in no case is there a declaration that this is a minimum spacing requirement. In particular, the text at the bottom of table 310.60 simply states that these figures have the dimensions associated with the tables that follow. Nothing requires you to use those figures. It?s just easier if you do, because then you can use the ampacity values in the following tables.
 
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