UL 508A Disconnecting Means Question

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MicahR

New User
Location
El Mirage, AZ
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.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I don't have my copy of UL508a handy but I don't recall that in general a main disconnect is required except for certain types of control panels.

The service equipment requirements only apply to service equipment and it seems unlikely this is service equipment. Service equipment is connected directly to the utility and this isn't.
 

Aleman

Senior Member
Location
Southern Ca, USA
I am not sure about the compliance of this as far as UL508A, but we have a panel along these same lines. The panel has 7 drives, a 24V supply, and an AC unit.
All components are fed by a panel-board outside of the cabinet. Everything is on it's own breaker no distribution blocks like you have. One of our guys designed
it and I built it. It's the only one like it and I don't know why he wanted to do it like this. In my opinion it's a screwy scheme. We do not get these listed so I don't
know if it would pass. Electrically it's all sound but to safe off the cabinet you need to switch off 8 outside breakers. I saw this post this morning and I was hoping
someone would have an answer because I have my doubts like you do.
 
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