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Old December 17th, 2015, 12:04 AM   #1
United States

Micah_68 is offline
Join Date: Jun 2013
Location: El Mirage, AZ
Posts: 6
UL 508A Disconnecting Means Question

I would like some input from those familiar with UL508A. I have a question on disconnecting means in a control panel.

There is a large motor control panel that is set up like this…. Within line of sight of the control panel, there are 480V and 208V panelboards. From the 480 panel breakers, six feeders come into the control panel, land on six sets of distribution blocks, and each distribution block feeds a group of 5-10 UL Type F manual motor starters. From the 208 breaker panel, two three-phase feeders come into the control panel, land on their own distribution blocks, and again feed groups of manual motor starters… also there are 7 single phase feeders feeding control power circuits, transformers, etc. So, there are a total of 8 three-phase feeders and 7 single-phase feeders with no main disconnecting means at the control panel (disconnecting means is at the panelboards is about 20ft away). If it matters, these panelboards also feed loads in the field other than this control panel… receptacles, lighting, etc.

Is this a violation of some sort? I haven’t seen this on other job sites. Now, I know UL508A 30.3.1 says that disconnecting means is not required if the control panel is marked in accordance with 60.1, but I have always thought of this as just a single disconnecting means… not 15.

Under the Service Equipment Use section, UL508A 75.4.3 states that no more than six disconnecting means shall be required to completely disconnect service to the industrial control panel. I am a little unclear on exactly what this applies to. Is this just for service entrance equipment? Or does this apply to the downstream control panels that it feeds? Would the main breakers on the panelboards count? In that case, there would only be two disconnects.

Thanks for any input.
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