Underground piping correction factor, how to apply it?

[PabloO]

Hi, we're trying to run independent wires to 12 or 20 similar-to-each-other loads, 1-ph, 240 V, up to 60A each, that might not be coincident in most of the cases, and that are restricted to 5 being coincident at full load. We'll go underground with individual PVC piping for each load, or as much as 2 loads bundled together (4 wires + ground). How should the bundling correction factor be applied if the pipes will go side-by-side, one with one load circuit?, like:

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in 2 or more beds/lines inside the trench (planning it to be min 24" depth); we have not found how should this correction be considered, if it's the same as if all the wires will go bundled together in a bigger pipe, or if having individual pipes helps to reduce or eliminate the correction factor

 

[PabloO]

hi again rewriting my doubt
how should the adjustment/correction factor be applied when bundling PVC pipes in an underground trench, each pipe with one 240V load circuit -2 wires- ?
And, where to read about this in the NEC?
Is Annex B (more) applicable to Medium Voltage than for Low Voltage?

 

[tom baker]

Well, conduit not pipes.

 

[electrofelon]

hi again rewriting my doubt
how should the adjustment/correction factor be applied when bundling PVC pipes in an underground trench, each pipe with one 240V load circuit -2 wires- ?
And, where to read about this in the NEC?
Is Annex B (more) applicable to Medium Voltage than for Low Voltage?

If you use the ampacity from the tables, then don't worry about it. Annex B is for ampacities calculated under engineering supervision.

 

[ptonsparky]

If you use the ampacity from the tables, then don't worry about it. Annex B is for ampacities calculated under engineering supervision.

Which means, if you're asking, you don't have it.

 

[PabloO]

thank you everyone, taking notes:
- I should refer to conduit not pipes
- Annex B is to be used under engineering supervision, that takes me to this question: who is allowed/certified to do this engineering supervision?
- but my main doubt is: do I have to use a bundling adjustment factor when using PVC conduit, each with a separate circuit? Which table would that be? I guess not Table 310.15(C)(1), which is for current-carrying conductors, not counduits.

 

[Julius Right]

The current rating [ampacity] for cable in cable ducts, in art. 310 and in Annex B, are for a distance of 7.5” between ducts [large conduits] and an Earth RHO of 90 W.cm/0C.If your case is different, you have to calculate it-as per Neher and McGrath or IEEE 835 or IEC 60287.If you have to be in NEC recommendations you have an engineer supervising. In my opinion the authority having jurisdiction has to state who may be this engineer.