Disconnect for 208V 3-phase automation control panel with 120v 1-phase loads

[kloc5]

For a 208V 3-phase automation control panel with 120V 1-phase loads connected between line and neutral, can a UL98 fusible disconnect be used as the main disconnect? The loads would be connected line to neutral without a transformer and therefore I was thinking 210.4(B) for MWBC would apply. All three phases would still be disconnected if you manually shut off the disconnect, but if a fuse blew, you could still have two live phases. I guess the other option would be to use a UL489 MCCB but this seems overkill for this small of a panel.

In the past, we typically have 480V 3-phase panels with a 1-phase transformer for our 120V loads.

Thanks!

 

[coop3339]

I'm not sure I follow completely but as long as you are using the correct size conductors and overcurrent protection with nothing exceeding its limits and all is listed for the use you should be okay.

 

[jim dungar]

Overcurrent protective devices are not required to open all 'live' conductors at the same time.

Disconnecting devices are typically required to open all of the live conductors.

 

[tortuga]

If any of the 120V circuits are for motor control I believe 430.75 requires all control circuits to be disconnected when the disconnect is open so you'd have a 4-pole disconnect. We had a recent related thread here:

Battle with Student

Another battle with a student. If you look at the appended jpeg you will find two schematics for a motor control circuit. “A” is my drawing. I had been taught that you cannot use Neutral as a switched conductor. I believe it is buried somewhere in code, but darned if I can find it. It is my...

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