Can I stuff multiple 480V 3 phase feeders in one conduit?

[Dylan]

I have a question about simplifying our installs. so, we've got several different 480V, 3phase loads, and instead of running individual conduits for each one, we're thinking of running all the load conductors (all three sets of 3phase power conductors) in one big conduit.

Does the National Electrical Code NEC allow running multiple separate 480V 3phase feeders in a single conduit? What NEC articles cover this? We're trying to save on materials and labor, so any insight on the rules here would be huge!

 

[Alan]

The NEC does not forbid putting several 480 volt feeders in one conduit, but you need to watch the derating rules once the conductor count climbs. Article 310 covers the adjustment tables. The other issue is heat buildup which can bite you more than the material savings. How many feeders were you planning to run together?

 

[PGB1]

Hi Dylan,
Are these actually feeders or are they branch circuit conductors?

You mentioned "several different ....loads", so I'm guessing branch circuit conductors. If they are feeders, you may be able to skip some grounded circuit conductors (neutrals), allowing for a smaller conduit. It all depends on the situation.

It is common practice to put several circuits of any voltage in one raceway (conduit, duct, etc.). We do it all the time under NFPA 70 & CEC, keeping in mind the rules Alan posted above. A job may call for me to install one raceway with a dozen or more feeder groups which eventually will go to separate panelboards. We do the same with service conductors.

If you have a whole bunch of circuits to run, consider electrical duct instead of traditional, round conduit. You can drop out of the duct anyplace with conduit for a load.
Or, consider bus duct and then sub panels or a switchboard at the destination- or even fused bus plugs along the way for loads.

 

[h0td0g]

yeah, you can definitely do this under NEC Article 310.15, but watch out for the ampacity adjustment factors. If you run three sets of 3phase conductors, that’s 9 current carrying conductors in one conduit. According to Table 310.15, you’ll have to derate your wire capacity to 70%. You might find that the money you save on conduit is eaten up by having to buy much thicker copper to meet the new ampacity requirements

 

[electroshak3]

yeah, I’ve done this to save space, but it’s a double edged sword
pulling three sets of 480V through one big pipe is a backbreaker compared to three smaller, easier pulls
plus, if one leg shorts out, it’s taking the whole pipe down with it
check Article 310.15 for the derating tables before you buy your wire. that’s usually the deal breaker