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Micah_68 December 17th, 2015 01:04 AM

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.

GaryS December 17th, 2015 01:59 AM

short answer
Yes many violations
6 sweeps of the hand to disconnect all power is the first and most dominant
Multiple power sources 480V down to 120 V from different sources
but the inspector is the one to make the call if I were you and your concerned ask for an inspection.
I recently worked on a large site where I noticed that the lock out tag out did not meet the current standards. when I asked about it I was quickly informed that the site was owned by a company in the UK and US standards and rules didn't apply here. they worked under UK rules. and if I questioned it again I would be escorted off site and charged with trespassing. this was in south central US. needless to say I saw many violations that I had to ignore. I find this happening a lot. Not much I can do about it.

jraef December 17th, 2015 10:02 AM

The "six hand rule" only applies to Service Entrances, the first point of connection to the utility source. It technically does not apply to a feeder circuit.

As noted, UL508A does not require a main disconnect switch. But UL508A only applies to how a "control panel" is built and wired, not whether or not it meets other applicable codes. Generally other codes tend to align with UL508A, but this is one area where they don't. The reason is, other codes can get more specific as to the TYPE of machinery being controlled, UL508A doesn't care, it's generic.

So if this application can be considered "industrial machinery", then NFPA79 applies to the control panel AS WELL, and NFPA79 DOES require that ALL external sources of energy be interlocked with the door so that you cannot open the door without interacting with the disconnect switch (and, by the way, the switch can still be operated with the door open without tools).

Then if the control panel is for HVAC equipment, there are different rules, many of which are in the NEC, or if it is a Semiconductor Tool, rules apply from SEMI F2, or if it's a robot, RIAA, etc. etc. etc. The devil is in the details.

FactoryTalktotheHand December 17th, 2015 11:53 AM

Quote:

Originally Posted by GaryS (Post 670770)
when I asked about it I was quickly informed that the site was owned by a company in the UK and US standards and rules didn't apply here. they worked under UK rules.

This sounds really suspicious to me. I am quite sure OSHA would heartily disagree with this. If it's on US soil, I would think US standards apply. I mean, it doesn't even make sense. The whole point of all these rules and regulations is to protect the safety of US workers and to lessen the need for public safety and rescue services. I assume these were all US workers and I'm sure if they building caught on fire they'd call the local American fire department. To simply say "US standards don't apply" sounds like an owner who doesn't want to face reality.

James Mcquade December 17th, 2015 01:33 PM

It doesn't matter who owns the company and from what country.

If it's installed in the USA it must comply with all federal and state regulations.

I worked for a UK company for 7 years and when we imported panels into the USA, we had to comply with the NEC 70, Nfpa 79, and other codes. This also applied to when we shipped panels to other countries as well.

Multiple power sources into one control panel MUST be defined on the panel.
I would not allow that into any plant I have worked at.

If someone gets injured or killed in this panel, the result will not be so nice for your company.

james

Bob O December 26th, 2017 02:05 PM

Sorry in advance for resurrecting an old thread but I'm in a similar spot.



A firm is proposing 1 – 120 VAC circuit to the control panel for the PLC and associated I/O. They are also proposing 3 – 480 VAC circuits into this same control panel that would feed three pumps from the control panel.


This isn't classified as an “Industrial Machine” through NFPA 79 so the door disconnect code from them doesn't come into play. The 480 breakers are in-sight and near the control panel.


This set-up doesn't feel right but I need more to go on and I'm not a code expert.


Any help is appreciated,
Thanks

NetNathan December 26th, 2017 04:41 PM

Quote:

Originally Posted by Bob O (Post 763277)
Sorry in advance for resurrecting an old thread but I'm in a similar spot.



A firm is proposing 1 – 120 VAC circuit to the control panel for the PLC and associated I/O. They are also proposing 3 – 480 VAC circuits into this same control panel that would feed three pumps from the control panel.


This isn't classified as an “Industrial Machine” through NFPA 79 so the door disconnect code from them doesn't come into play. The 480 breakers are in-sight and near the control panel.


This set-up doesn't feel right but I need more to go on and I'm not a code expert.


Any help is appreciated,
Thanks

Why not (1) 480 supply disconnect for all three pumps (on their own protection in panel) and a 480/120 control transformer for control?

jraef December 27th, 2017 12:11 PM

Your instincts are correct in that having no means of disconnect would be a safety concern, but if the 480V breakers that you mention are within sight, and there are Lock-Out provisions on them, then that is acceptable so long as the proper signage is on this control panel.

Next time, start a new thread and reference the old one if you feel it's pertinent.


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