Load break or non load break. That is the question?

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kda3310

Senior Member
How can I tell if our GE Heavy Duty Safety Switches 30 Amp 600 Volt Max HP 30 NP1578000G is rated for load breaking or not? Also, where could I look up some documentation to show my employer if they are or are not? :?
 

jim dungar

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Staff member
Location
Wisconsin
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Retired Electrical Engineer - Power Systems
How can I tell if our GE Heavy Duty Safety Switches 30 Amp 600 Volt Max HP 30 NP1578000G is rated for load breaking or not? Also, where could I look up some documentation to show my employer if they are or are not? :?
If it has a HP rating it is load break.
 

kda3310

Senior Member
That sounds good and I have always thought if it had switch in the name it was rated for switching or load breaking. However do to my maintenance superintendent who knows nothing about electricity reading an article about disconnects being shut off under load and exploding we can not shut any of our machines down using the safety switch any more. Seeing I like my job I am not going to tell him anything unless I can show him something, I could really use some help.
 
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jim dungar

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Staff member
Location
Wisconsin
Occupation
Retired Electrical Engineer - Power Systems
The difference between a 'current rated' device and a 'listed HP rated' one, is the requirement for being able to make and break the Locked Rotor current of the motor.

I t is absolutely true that not all 'safety switches' or 'disconnect switches' are rated for controlling motors. There have been many recorded misapplications of 'Lock Out/TagOut' switching devices particularly the 'small ones' found on conveyors.

You should get a copy of the UL White Book and check the listing of your device.
 

kda3310

Senior Member
I guess I thought GE would list this kind of info on a spec sheet for the disconnect. I was really hoping for something in layman's terms saying it is or is not. I have looked up some Industrial Buyers Guides trying to get this info with no luck. The time it takes to climb from one side of the machine to the other verses just locking out the Safety Switch increases our down time. The new rules they have implemented does not allow for more down time. They just want us to work faster and don't get hurt. You know "Safety First After Production". I am certified with OSHA from a 30 hour class for industry and a 30 hour class for construction with a 10 hour refresher class. I have found the general rule is OSHA hires experts to give a minimum standards leaving an opening for companies to be able to set rules above and beyond the minimum. Then companies hire kids strait out of college for there safety programs who have not even seen or know how to work on these machines to set the above and beyond standards. So, experts give us the minimum and idiots give us the beyond.
 

kwired

Electron manager
Location
NE Nebraska
That sounds good and I have always thought if it had switch in the name it was rated for switching or load breaking. However do to my maintenance superintendent who knows nothing about electricity reading an article about disconnects being shut off under load and exploding we can not shut any of our machines down using the safety switch any more. Seeing I like my job I am not going to tell him anything unless I can show him something, I could really use some help.

I would be more concerned about closing switch into an unknown fault than opening a switch carrying rated load or less.

Closing a switch into a locked rotor condition maybe next concern that is still a higher concern than opening a switch carrying rated load.

I don't know what ratings of these switches are but don't feel it is a good idea to use them as a regular control method. Occasional emergency use as a way to shut something off I don't feel is a problem. Likely the reason for emergency shut off is more important at the time than worrying about what damage may happen to the switch.
 

kda3310

Senior Member
I don't know what ratings of these switches are but don't feel it is a good idea to use them as a regular control method. Occasional emergency use as a way to shut something off I don't feel is a problem. Likely the reason for emergency shut off is more important at the time than worrying about what damage may happen to the switch.

Yes, that's right. We have motor starters in all the MCC buckets just for that purpose ahead of the safety switch that I am talking about using for motor controlling. If I understand it right, if I turned on that safety switch with a motor control in line with it and the motor is locked up then the thermal overloud or the breaker with a set trip curve on it should trip before something bad happens. Am I thinking right or wrong on this?
 

kwired

Electron manager
Location
NE Nebraska
Yes, that's right. We have motor starters in all the MCC buckets just for that purpose ahead of the safety switch that I am talking about using for motor controlling. If I understand it right, if I turned on that safety switch with a motor control in line with it and the motor is locked up then the thermal overloud or the breaker with a set trip curve on it should trip before something bad happens. Am I thinking right or wrong on this?

If motor is locked up then the switch will see locked rotor current and should be designed for this.

If the switch would be closed into a fault it could see much more than locked rotor current. It likely contains the arc flash to a reasonable extent but all bets are off as to whether or not the switch is usable again. Most of the time it probably will be.

Yes the branch circuit protection and motor overload protection still do their duties.
 

kda3310

Senior Member
You do not see the red stamp in the upper righthand corner, of the 'yellow label' that says Underwriters Lab?

Yes, now that you pointed it out to me. :jawdrop: I believe you are right that it is rated for load breaking. But, how can I show my boss that I can shut it down using this switch. I know you said I should get a copy of the UL Wight Book but, I live in a rule area and stuff like that is not ready available to me. Do you know if a PDF copy of this book is online that I can print out the pages I need?
 
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