If i use 3c10awg MC cable for cabling 10 hp 460V motors, in accordance with table 310.15(B)(2)(a), i can make a bunch of 10 of this cable. My question is how many space it should have bettween this bunch of cables and another bunch of cables. (i mean in a ladder cable tray)
[This message has been edited by Bobby Mercier (edited 11-28-2002).]
Space means just that, as in no contact between the bundles. Since no specific dimension is given, if you can see a crack of light between the bundles, they meet the definition of the word "spaced."
Look at 392.11(A). This section is not real clear to me, and (A)(1) appears to conflict with (A)(3).
Don
Don has a very good point & I could see a fistfight or two breaking out over it. Maybe you need to space the bundles 1 bundle diameter apart.
I feel I correctly answered your question about space in the ordinary sense, but I didn't do so in the context of your question.
In any case, since you are dealing with #10 conductors, it appears that 310.15(B)(2)(a) would require a derating to 45%. Therefore, #10 would be OK since its final ampacity is more than 125% of the 14 amps the motor draws.
It would be interesting to apply Exception 5 to 310.15(B)(2)(a) by using #12 & supporting on bridle rings instead of cable tray. What do you think?
Don
I believe that 392.11(A)(1) applies to the cable assembly. eg a 10-3 mc cable vs a 10-5 mc cable where you may have more than 3 current carring conductors in that one cable.
I believe that 392.11(A)(3) applies to the total # of cable assemblies installed in the tray.
Keeping cable assemblies seperated is a good practice.
I think if i respect table 392.9 i don't have to derate cable.
Do you thing it's OK