Motor controller/plc cabinet disconnect

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wireman71

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Does a built in disconnect in a motor/PLC controller cabinet meet the disconnect requirements of Article 430? It has a rotary type disconnect that prevents the door from being opened unless the disconnect has been opened. This disconnects all voltage inside the unit except for the circuit wires feeding the line side of the cabinet disconnect. Inside are the PLC's and motor controllers for the equipment.
 
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wireman71 said:
Does a built in disconnect in a motor/PLC controller cabinet meet the disconnect requirements of Article 430? It has a rotary type disconnect that prevents the door from being opened unless the disconnect has been opened. Inside are the PLC's and motor controllers for the equipment.
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Does it meet the requirements of chapter 9 of 430? And it sounds like a safety switch.
 
Most of these devices are not UL rated for use as a disconnect. If you read the fine print from the manufacturer normally the words ?... designed for use as local motor isolation and IEC disconnect switch applications outside North America ...? will be found. Many of the devices which were originally designed to IEC standards do not meet the current UL requirements for distance between terminals, load interrupting, etc. I think the load interrupting rating may be the problem with these particular devices, someone once told me that they could be used in an application where a motor was already shut off and a lock-out point was needed. Although devices based on IEC standards have been successfully used in Europe for many years they have limited applications in the US market.
 
Thanks! So it doesn't have to do with the fact that there is circuit voltage present in the cabinet to the disconnect but with the issue of the disconnect being properly rated.
 
gwpowell said:
Most of these devices are not UL rated for use as a disconnect. If you read the fine print from the manufacturer normally the words “... designed for use as local motor isolation and IEC disconnect switch applications outside North America ...” will be found. Many of the devices which were originally designed to IEC standards do not meet the current UL requirements for distance between terminals, load interrupting, etc. I think the load interrupting rating may be the problem with these particular devices, someone once told me that they could be used in an application where a motor was already shut off and a lock-out point was needed. Although devices based on IEC standards have been successfully used in Europe for many years they have limited applications in the US market.
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Who told you that? The NEMA disconnect salesman? There are many of these style disconnects that are UL rated. Check the literature to be sure one way or the other. Often the UL ratings are lower than the IEC ratings.
 
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gwpowell said:
Most of these devices are not UL rated for use as a disconnect.
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There are "control panel" door mounted rotary switches which are UL listed as disconnect devices.

Some of the "individually enclosed" rotary switches are non-load break isolation switches and not rated for make/break of fault current. Though, several "name-brand" manufacturers have versions with UL Listings.
 
A UL98 listed disconnect would meet the necessary requirements or a UL508 disconnect marked "suitable as motor disconnect"
 
MO_EE said:
A UL98 listed disconnect would meet the necessary requirements or a UL508 disconnect marked "suitable as motor disconnect"
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I would say that a UL508 motor disconnect is not listed to be the main panel disconnect means. My 2001 ed. of UL508A requires disconnecting handles and operating mechanisms to comply with either UL489 or UL 98 standards (30.1.7).
 
petersonra said:
Who told you that? The NEMA disconnect salesman? There are many of these style disconnects that are UL rated. Check the literature to be sure one way or the other. Often the UL ratings are lower than the IEC ratings.
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No the "NEMA disconnect salesman" did not tell me this I read it for myself in the manufacturers literature and you will notice that I used the word ?most? not ?all?. Why would the manufacturer state this a device is not rated for an application if it actually is? After all they are in the business of selling components. You seem to berate me for my cautionary advice on these devices and then you go on to say that ?many? are UL rated. If only ?many? are UL rated then wouldn?t it be prudent to make sure the one you chose is properly applied to the application? I thought the purpose of this forum was to help each other and learn more about our trade but replies such as this one really sour me on the whole process.
 
wireman71 said:
Does a built in disconnect in a motor/PLC controller cabinet meet the disconnect requirements of Article 430?
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430.?? what ? If you mean 430 IX. Disconnecting Means, they I say Yes, the disconnect for the panel is all that is needed, as long as it's lockable open/off AND HP rated.

While I mostly use flange mounted handle disc.'s, at times I do use rotary ones.

Why not post the mfg / model number for us to see ?
 
I would say that a UL508 motor disconnect is not listed to be the main panel disconnect means. My 2001 ed.
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The latest version of UL508 is Sept 1, 2005 and MO_EE is correct:
A UL98 listed disconnect would meet the necessary requirements or a UL508 disconnect marked "suitable as motor disconnect
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Which will have a marked hp rating that is capable of being locked out and tagged out (NFPA-79).
Disconnect switches are hi-lited in section 30 "30.1.4 A switch unit, an open-type switch or enclosed switch shall comply with the requirements in the
Standard for Enclosed and Dead-Front Switches, UL 98."
This would seem to satisfy 430.74 Disconnection and 430.109
Just my $.02
 
davidr43229 said:
The latest version of UL508 is Sept 1, 2005 and MO_EE is correct:

Which will have a marked hp rating that is capable of being locked out and tagged out (NFPA-79).
Disconnect switches are hi-lited in section 30 "30.1.4 A switch unit, an open-type switch or enclosed switch shall comply with the requirements in the
Standard for Enclosed and Dead-Front Switches, UL 98."
This would seem to satisfy 430.74 Disconnection and 430.109
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My quote of UL 508A should have been in regard to the enclosure's operating handle (in 2001 this was 30.1.7) and not the disconnect mechanism which clearly is addressed by 30.1.4. Also back in 2001, enclosure disconnects for industrial machinery panels (like those in NFPA 79) were addressed by UL508A in 66.1.5.

Just for my knowledge are these sections still in UL508A 2005?
 
Just for my knowledge are these sections still in UL508A 2005?
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Jim:
66.1.5 A door of an enclosure that gives access to uninsulated live parts operating at 50 volts rms ac or
60V dc or more shall be interlocked with the disconnecting means such that none of the doors can be
opened unless the power is disconnected.
Exception: A disconnecting means for maintenance lighting circuits or for power supply circuits to control
devices with memory requiring power at all times are not required to be interlocked with the enclosure
doors. The cautionary marking in 55.4 shall be provided.
Revised 66.1.5 effective March 1, 2007
and:
66.1.5.1 The interlocking means required by 66.1.5 shall be provided with all the following:
a) Means to defeat the interlock without removing power and which requires the use of a tool to
operate;
b) Means to prevent restoring power while the enclosure doors are open unless a defeat
mechanism is operated; and
c) Reactivated automatically when all the doors are closed.
Added 66.1.5.1 effective March 1, 2007
Dave
 
Jim:
For your review.
Is 30.1.7 still in there
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30.1.7 Disconnect handles and operating mechanisms shall comply with the requirements in the
Standard for Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures, UL
489, or the Standard for Enclosed and Dead-Front Switches, UL 98, or the Standard for Industrial Control
Equipment, UL 508, for use with the disconnecting device involved.
30.1.7 revised September 1, 2005
Dave
 
davidr43229 said:
Jim:
30.1.7 Disconnect handles and operating mechanisms shall comply with the requirements in the
Standard for Molded-Case Circuit Breakers, Molded-Case Switches, and Circuit-Breaker Enclosures, UL
489, or the Standard for Enclosed and Dead-Front Switches, UL 98, or the Standard for Industrial Control
Equipment, UL 508, for use with the disconnecting device involved.
30.1.7 revised September 1, 2005
Dave
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Thanks,
The option for a UL508 mechanism is a change from the 2001 edition.
 
Jim,
Welcome
In my opinion what we are seeing within the Industrial Control world is a harmonization of NFPA-79, IEC60204-1 and IEE1584 all into 1 standard (UL508A). NEC 2005, UL508A was only meant to be introduced as a guideline, as so introduced as a FPN within article 409.
Almost by default UL508A rose to the top as "The Standard" on April 25, 2006, due to no other standards encompasing so many other standards.
Hope this helps.
Dave
 
I hope between Dave and Jim that one doesn't lose his keys or easter eggs and the other doesn't say something he doesn't mean. You know what I mean?
 
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