Grouping Multiple Motor Conductors in Same Raceway

[paulgarett]

All phase conductors (10 AWG THHN) for five 10 hp, 480 volt motors are grouped in the same raceway, 1" PVC, for about 100 feet and end at a junction box. From the junction box flex is run to each individual motor.
If these motors are on continuously, would grouping 15 conductors (5 motors x 3 phase) plus ground in the same raceway create heating and cause the motor starters to trip?
One of these motors start-up current is between 75-90 Amps. Their running current is about 14 amps. The five motors are on timers so they don't come on at the same time. One comes on immediately, five seconds later 2 more come on, five more seconds, 2 more come on for a total of five. The start-up current is quite large. The 10 AWG was not sized for 75-90 amps. I am worried the magnetic induction of the conductors in the raceway are causing the motor starters t to trip.

 

[weressl]

All phase conductors (10 AWG THHN) for five 10 hp, 480 volt motors are grouped in the same raceway, 1" PVC, for about 100 feet and end at a junction box. From the junction box flex is run to each individual motor.
If these motors are on continuously, would grouping 15 conductors (5 motors x 3 phase) plus ground in the same raceway create heating and cause the motor starters to trip?
One of these motors start-up current is between 75-90 Amps. Their running current is about 14 amps. The five motors are on timers so they don't come on at the same time. One comes on immediately, five seconds later 2 more come on, five more seconds, 2 more come on for a total of five. The start-up current is quite large. The 10 AWG was not sized for 75-90 amps. I am worried the magnetic induction of the conductors in the raceway are causing the motor starters t to trip.

Derating for 40C ambient and multiple conductors still give you 15.4A on a #10AWG THHN, so I would say there is no problem. Wiring is not sized for inrush current, which is about 600% in your case, nothing unusual. (Should you have these motors on Adjustable Speed Drives, then you may see problems, but those would be a set of different issues, not (just) overload.)