Using Industrial VFD as Power Distribution Point

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freecrowder

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I am looking at supplying power from the input side of a VFD to another load. This would be on the output side of the drive circuit breaker. The load would be supplied from a switched fuse device with proper ratings. I will try to attach simple drawing. My question what does NFPA 70E say about doing something like this.
 

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Feeder tap rules would apply, so yes, you can do it if you read those rules carefully. How do you plan to make the tap off? that's an important consideration because if the existing CB does not have provisions for doubling up on the conductors, you will have to add a distribution block too, and not you have to start worrying about having proper clearances and wire bending space. most enclosed circuit breakers do not give you a lot of extra room.
 
There's nothing inherently wrong with what is being proposed. As another poster mentioned there are some tap rules that need to be followed, along with some practical things like how you're going to make the tap and the available space in which the tap has to be made.

There's also the possibility that the combined ampacity requirements of the VFD and the new load exceed the ampacity of the conductors feeding the VFD, which would make this a no-go.

If you meet all the criteria you might be able to find some insulation displacement connectors that you could use to make the tap.
 
Thanks for the responses. I agree the biggest issue might be the tapping if the breaker has no provision for. That could be very likely bc the conductors in and out (breaker) will be 200MCM to 500MCM and I will tap in with 12ga conductors. I have seen people drill the conductor block of the breaker and tap with a screw and then attach 12 ga. wire with ring terminal to screw. Anyone know if that would comply to codes? Or can you wrap the 12 ga. around the larger gauge and then place under compression block of breaker?
 
freecrowder said:
Thanks for the responses. I agree the biggest issue might be the tapping if the breaker has no provision for. That could be very likely bc the conductors in and out (breaker) will be 200MCM to 500MCM and I will tap in with 12ga conductors. I have seen people drill the conductor block of the breaker and tap with a screw and then attach 12 ga. wire with ring terminal to screw. Anyone know if that would comply to codes? Or can you wrap the 12 ga. around the larger gauge and then place under compression block of breaker?
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There are some breaker lugs that come with a tapped hole for a screw connection. I find them handy for control power transformers.

I do not think tapping an existing lug is an acceptable modification, even though I know it is pretty common.

Most lugs are not rated for more than 1 conductor, but you might be able to find some appropriate IDC connectors if it is a single conductor application and not parallel conductors.

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