Combining motor circuits

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mstrlucky74

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NJ
If you had some motors that are 20&30a circuits would you combine the circuits in one conduit if in the same area or do you run a separate conduit for each circuit???? I know the spec sometimes dictates. But I hear different opinions on this regarding motors.
 
If they are simply AC Poly-phase or single phase motors with across the line starting there is definitely no problem in sharing a conduit. Keep derating in mind.
 
Code wise it makes little difference mostly, although it could affect derating issues, but probably will not.

VFD wise, it probably makes no difference but it might.
 
Nope, but I did stop them from trying to poke each others eyes out.
One set of VFD output wires which are not designed for VFD use can experience standing wave problems. Putting two different VFD outputs in the same raceway, running at different frequencies at different times just increases the potential problems.

Tapatalk...
 
mstrlucky74 said:
Ok, got it but we are talking line voltage wires only, not control right?
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while you can put control wires in with the motor control wiring in the same conduit, if the insulation for both
is sufficient for the highest voltage present, and you can combine motors in the same conduit, provided you
use appropriate derating, but you would be a flaming fool to do that with VFD's, which modify voltage and frequency,
and parallel conductors will have induction, the longer the run, the more the induction.

if you don't understand why induction and harmonics are a problem here, then that is a problem in itself.
 
Fulthrotl said:
while you can put control wires in with the motor control wiring in the same conduit, if the insulation for both
is sufficient for the highest voltage present, and you can combine motors in the same conduit, provided you
use appropriate derating, but you would be a flaming fool to do that with VFD's, which modify voltage and frequency,
and parallel conductors will have induction, the longer the run, the more the induction.

if you don't understand why induction and harmonics are a problem here, then that is a problem in itself.
Click to expand...

I think you are well advised not to run multiple sets of motor feeders in the same conduit if they are VFD controlled. But, people do it on an almost routine basis, especially with smaller motors. While I believe doing so is well below sub-optimal, I have yet to see a case where there were any actual negative effects from such an installation. that does not mean i think it is a good idea or that there has never been a case were doing so resulted in some negative effect.
 
petersonra said:
I think you are well advised not to run multiple sets of motor feeders in the same conduit if they are VFD controlled. But, people do it on an almost routine basis, especially with smaller motors. While I believe doing so is well below sub-optimal, I have yet to see a case where there were any actual negative effects from such an installation. that does not mean i think it is a good idea or that there has never been a case were doing so resulted in some negative effect.
Click to expand...

There shouldn't be any problem running the line side wiring to the VFD'S in 1 conduit is there? Then obviously have 2 separate conduits going to the motors?
 
gk351 said:
There shouldn't be any problem running the line side wiring to the VFD'S in 1 conduit is there? Then obviously have 2 separate conduits going to the motors?
Click to expand...

I probably should not have used the term motor feeders when I really meant the wires going out to the motors.

I don't see any problem running the line side conductors to the VFDs in the same conduit.
 
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