motor disconnect location

[ibew501ed]

In a powerhouse, we have 6 large MCC's that feed everything from 200hp
480v motors to motor operate 1/4 hp valves. Are disconnect switches required at each motor as per 430.102(B) or does the exception become the rule in the situation described above.
thanks for any input
ps engineers don't show disc sw's

 

[Cold Fusion]

In a powerhouse, we have 6 large MCC's that feed everything from 200hp
480v motors to motor operate 1/4 hp valves. Are disconnect switches required at each motor as per 430.102(B) or does the exception become the rule in the situation described above.
thanks for any input
ps engineers don't show disc sw's

Generally speaking, in industry, 430.102.B.2.exception.b is the rule. Ocassionally (rarely) disconnects are located at the motor.

cf

 

[augie47]

cf,
May be a regional thing, but in this area there is a lot of small industry where 430.102(B)(2)(b) is not the case and not requiring the disconnects iis "rare".
In the OPs situation I would imagine the exception applies.

 

[ibew501ed]

thank you both
just wanted some reassurance

 

[Cold Fusion]

... May be a regional thing, but in this area there is a lot of small industry where 430.102(B)(2)(b) is not the case ...

Is that because the AHJ does not use a normal English language interpertation of the NEC, but rather rules by decree?

Or is it that the "small industry" does not meet the requirements of 430.102(B)(2), Exception (b)?

And yes, I've seen one installation where the engineering specified 200hp rated, C1D1 disconnects located at the motor. I never could get an answer out of them as to why. Damn morons with a state job budget and little oversight - enough to make one sick.

cf

 

[augie47]

It seems here that many small industries do not "have written safety procedures, where conditions of maintenance and supervison ensure that only qualified persons service the equipment" so they do not meet the requiremnts to allow the exception.

 

[kwired]

where conditions of maintenance and supervision ensure that only qualified persons service the equipment

that is the key phrase. What the AHJ will allow as meeting this could possibly be different in one jurisdition than it is in another. So it is ultimately up to the AHJ. Now factor in other things like OSHA requirements and every place should have qualified persons and documented procedures. But we also know that does not always happen especially in smaller facilities.

add: I see augie beat me to posting practically the same information.

 

[Cold Fusion]

It seems here that many small industries do not "have written safety procedures, where conditions of maintenance and supervison ensure that only qualified persons service the equipment" so they do not meet the requiremnts to allow the exception.

That makes sense and would certainly not be "regional".

... What the AHJ will allow as meeting this could possibly be different in one jurisdition than it is in another. So it is ultimately up to the AHJ. ...

Those are the ones that I find offensive/unprofessional - the AHJs that don't own a Funk and Wagnalls, and rule by decree.

And yes, you are absolutely correct, "So it is ultimately up to the AHJ." To paraphrase one of our menbers - Truth is a function of power. Has nothing to do with physics, or right.

cf

 

[dicklaxt]

In industry,the PID's(Piping Instrument Diagram"s) prepared by the engineering company would normally have a blurb in the General Notes stating yea or nay on this requirement and that note has gone thru a client review and approved such as is stated.The Electrical General Specifications for that particular contract will also cover this and should be in agreement with the PID's.This specification is also prepared by the engineering company.The client will oft times direct the engineering company to follow plant procedures and specifications as well so it is not something that is haphazardly decided upon.In the event that it is a question/requirment to be against code/safety in any manner,a letter addressed to the Engineering,relieving them of any liabilities is put into place.This will sometimes force the client to have a self insured facility.

In todays reduntant DCS logic(sometimes triple reduntancy) the Operators as well as the Electricians have to work together in motor check out/maintenance .The Electricians will physically lock out the controller at the MCC and the Operators will defeat energization with a DCS keypad fucntion so it is really quite safe IMO to follow the code ,,,,Not Required


dick

 

[Cold Fusion]

In industry,the PID's(Piping Instrument Diagram"s) prepared by the engineering company would normally have a blurb in the General Notes stating yea or nay on this requirement and that note has gone thru a client review and approved such as is stated. ...

I didn't know it was normal to put local disconnects on the P&ID - definitely see them on the one-lines

cf

 

[dicklaxt]

Check the PID General Notes or the General Specs ,it has to be addressed.In the event that it fell thru the crack on a particular contract on/oin those two documents,I'll bet correspondence records will cover it.Engineering /Design would not be able to function without that answer,single lines,schematics,wiring diagrams, motor control logic loops,cable tray fill ,cable schedules,physical plan dwgs,material budget items etc, all need to know this requirement.

dick

 

[Cold Fusion]

Check the PID General Notes or the General Specs ,it has to be addressed. ...

...Engineering /Design would not be able to function without that answer,single lines,schematics,wiring diagrams, motor control logic loops,cable tray fill ,cable schedules,physical plan dwgs,material budget items etc, all need to know this requirement. ...

That would be part of the reason I don't see them on P&ID. The design and majority of construction is a done deal by the time I get at it. Other than startup/commissioning I don't deal much with the design firms. I don't think I've ever seen P&IDs with general design notes.

The other reason is that Local Disconnects are so rare that I wouldn't be looking for them on a P&ID - even if they were there. But I would see them when I was going over the one-lines.

cf