Temporary feeder on roof/outside

[ceng728]

Hi all,

I have a project in NJ where we need to run a temporary 480V, 300A, 4W+G feeder from a panel in the penthouse level down to the lower level of a 4 story building. The plan is to run this feeder out of the penthouse, along the rooftop, and then down the side of the building to the ground, and enter into the lower level mechanical room through an air intake grate. The client would like to run this temp feeder using an outdoor rated cable. Would a Type G multiconductor cord or Type W single conductor cords be suitable for this install?

Also, I know that raceways and cable on rooftops are subject to derating, I assume this also applies to temporary cables, but my understanding is that if the cable is supported 7/8" above the roof, it does not need to be derated further than what's required for the ambient temperature in the area.

Thanks,
Chris

 

[zbang]

How long is "temporary"? If you're within the confines of art. 590 then G or W could be suitable if properly supported both across the roof and down the building, and protected from physical damage as needed. Remember that fine-strand cable requires lugs listed for that use, not all of them are (not that it stops a lot people...).

As for derating, I think you're correct but would have to check in the code to be sure.

Are you planning to rent or purchase the cable? A long-term rental may pencil out to more than the cost of EMT and aluminum wire; at which point you're probably out of the time limits in 590 anyway.

 

[ceng728]

Temporary would only be within the period of construction. The temp feeder will be used to temporarily feed loads from the penthouse substation to aid in cutovers while the lower level substation is being replaced.

 

[augie47]

IMO, Based on the wording in 400.5 you would need to apply 310.15(B)(2)