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Thursday, March 21, 2019
The Motion Control Community Forum, sponsored by Control Technology Corporation.
Can I Split Off 110V from 220V L1 (or L2) and Neutral?
Will I be breaking codes powering 110V equipment in a 220V enclosure using L1 (or L2) and neutral without a step-down transformer?

Will I be breaking codes powering 110V equipment in a 220V enclosure using L1 (or L2) and neutral without a step-down transformer?

I am in the process of designing a new industrial control cabinet for a CNC machine at work. The machine is powered by 220V. Both L1, L2, neutral, and ground terminate within the cabinet. The VFD for the spindle motor, the power supply for the stepper motors, and the power supply for the PLC all run off 220V. However, we would like to add a 1.5HP 110V flood coolant pump as well as a 110V outlet for a computer off the same enclosure. One idea was to simply power the pump and computer outlet with L1 (or L2) and neutral. Can anybody let us know why this wouldn't be a good idea, and if so, what codes we would be violating doing this? I'be been reading through NFPA 79 and haven't found anything that prohibits this practice. We wouldn't have even considered this unless neutral was terminated within the control cabinet (something you don't always see on 220V equipment).

From some questionable online posts I've read, it seems that this is accepted practice, with the caveat that you should never run multiple 110V devices off L1/neutral and L2/neutral. You should pick either L1 or L2 only. This prevents a technician in the future from possibly jumpering two 110V devices and inadvertently supplying a 110V device with 220V while attempting to troubleshoot a problem.

I've seen one example where a control enclosure was supplied by both 220V and 110V supply lines to accomplish the same thing we're trying to do, but it seems silly to run a separate 110V line to the control enclosure when you have 110V right there already thanks to the neutral.

Am I missing anything?

Thanks.

It is perfectly OK.

House wiring does it, no electrician is accidentally making 220 VAC. All 220V appliances like stoves and dryers do it to get 110VAC for controls and outlets.

Make sure that you properly label and colour code both L1 and L2, every wire at both ends. Add some labels about 110/220 VAC present with L1/L2.

Your cabinet design will be good.

good luck