Line and Load side conductors in same J-box

[mikegoetz]

We have a junction box with line side conductors feeding through to a VFD and the load side conductors come to the same j-box and feed through to a 250 hp motor. Do we need seperation in the j-box by some type of barrier? Line and Load conductors are installed in different conduit systems, but are installed in the same j-box. Does that cause harmonic distortion? Need to know what to do, because the compressor motor vibrates heavily and don't know if it is an electrical problem or an unbalanced coupler on the motor or bad bearings.

 

[ozark01]

My first question would be is this a new installation that has never worked properly or is it an existing installation that has work properly until recently? And second.....did you take the coupling loose and see if the vibration goes away?

 

[mcclary's electrical]

Too little info, but I suspect alignment problems more than harmonics.

 

[Sierrasparky]

I don't see the issue of line side load side in same junction box.
I'm sure there was a reason at the time.

 

[Wes G]

Generally my experience says there is no problem with these being in the same junction box as long as there are no splices, or if there are, the conductors for the differant systems are properly identified. Harmonic distortions can mess with electronic control equipment especially if the VFD is large. In that case you might want to use a line reactor to clean your electrical noise but doubt that it would ever cause problems with the compressor. If this is a new instalation and it still sounds bad (growls) with the coupler off, I would be inclined to double check the wiring of the motor leads.