Tray to Tray Cable Drop

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gjabei

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What is the maximum distance allowed by code for a cable drop from one cable tray to another?

1.) Cables are 3 - 3/C # 750 kcmil w/ #1 ground conductor - type TC.

2.) Cable Trays are 36" aluminum, ladder type.

3.) Cable Tray Article 392.30(B)(3) says 6 feet.

4.) I expected that distance to be defined in Article 336.30 (but that section does not exist in the 2011 code).

5.) I understand that Article 336.24 (Cable Bending Radius) factors into this, but I want to know the maximum distance.
 
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If you take a legalistic approach, then 336.10(7) onlyallows TC-ER to drop 6 ft. It does notaddress ?regular? TC cable. So justapplying 336.10(7) without any other thought means ?regular? TC cannot drop anydistance without being supported. Conversely,392.30(B)(3) allows ?individual conductors? to drop 6 ft. unsupported betweencable trays. So being practical insteadof legal, does it make sense that a small, flimsy individual conductor can drop6 ft. unsupported, but a beefier, 3/C TC cable can?t? So the question still remains ? how far can a?regular? TC cable drop unsupported between cable trays?
 
It seems Dennis answered and you confirmed the answer. If it's not TC-ER the allowable distance is zero. May not be logical or the one you want, but it's the NEC answer. "Approval" is up to your AHJ as noted in 90.4.

(side note 392.30(B)(3) what Code cycle ? )
 
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I do see where the OP is coming from. The way I read 392.30(B)(3) it seems to say that an individual TC can span the 6' between cable trays but the last sentence seems to say they shall be protected from physical damages by guarding.

I see 336.10(7) exception as saying that TC-ER is allowed to be run 6' unsupported between the Trays as long as it is protected from physical damage.

So the question is why can't regular TC be used for the 6'. IMO the NEC has made an oops here and I believe the TC can be run 6' if it is guarded
 
Dennis Alwon said:
I do see where the OP is coming from. The way I read 392.30(B)(3) it seems to say that an individual TC can span the 6' between cable trays but the last sentence seems to say they shall be protected from physical damages by guarding.

I see 336.10(7) exception as saying that TC-ER is allowed to be run 6' unsupported between the Trays as long as it is protected from physical damage.

So the question is why can't regular TC be used for the 6'. IMO the NEC has made an oops here and I believe the TC can be run 6' if it is guarded
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I agree. (I looked at my "2011 Draft" 1st and (B)(3) wasn't there unusual)
My Handbook does make note that "Standard" TC is governed by (7).
Sounds like a good opportunity for a CMP submital
(When I have time I'll try to research the ROC's since this was changed after the "draft")
 
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