MCC Test Point Outside Bucket?

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engtim

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OK, so we have some MCC's that are HRC3. There are some buckets that need to be shut down for maintenance fairly regularly. The question is, has anyone seen a mechanism for verifying a Lockout outside of the bucket door? It would be so much safer and efficient to perform a verification this way.

I do not believe the "Voltage Indicators" that are out there are valid for this application since there is no practical way to test the indicators after you shut off the power (test the tester - test for voltage - test the tester).

An initial thought was to install test points on the bucket door with a cover and label identifying them as verification test points.

Anybody want to play Devil's Advocate?

If this has come up in the past, please direct me to the appropriate thread.

Thanks...
 
zog

zog

Senior Member
Location
Charlotte, NC
engtim said:
OK, so we have some MCC's that are HRC3. There are some buckets that need to be shut down for maintenance fairly regularly. The question is, has anyone seen a mechanism for verifying a Lockout outside of the bucket door? It would be so much safer and efficient to perform a verification this way.

I do not believe the "Voltage Indicators" that are out there are valid for this application since there is no practical way to test the indicators after you shut off the power (test the tester - test for voltage - test the tester).

An initial thought was to install test points on the bucket door with a cover and label identifying them as verification test points.

Anybody want to play Devil's Advocate?

If this has come up in the past, please direct me to the appropriate thread.

Thanks...
Click to expand...

Very good topic, I have been in this discussion many times, and have discussed it at safety conferences in a round table format too. No one really has a system out there that meets the 70E requirements and it viewed as reliable by guys on the IEEE and 70E commitees. Good old method is still the best. Now you may want to look at reducing your HRC 3 areas via mitigation.
 
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engtim

Member
I have considered the graceport device (I refered to it as a voltage indicator above) but like you said, it doesn't satisfy the live-dead-live requirement without some kind of relay setup, and that open us up to other problems.

I can mitigate some areas by changing fuse sizes on some feeder breakers but not all (still in the middle of the power system study). Some MCC's have large motors and the fear is blowing a feeder breaker fuse on start up. In a chemical plant, that would introduce a whole new set of hazards.

So, I'm going to ramble a little here so please bear with me.
My thought was this:
Banana type terminals on the MCC bucket door (total of 4).
Small hinged cover labeled as LOTO verification test point.
Small guage wire (#16 type TFF -for flexibility) tied to the load side of the bucket fuses or with a separate fuse block for larger starters.

This could aid in troubleshooting as well with the door closed. I think I would probably make it procedure to open the the door after testing to get a visual verification that the switch opened.
 
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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
engtim said:
So, I'm going to ramble a little here so please bear with me.
My thought was this:
Banana type terminals on the MCC bucket door (total of 4).
Small hinged cover labeled as LOTO verification test point.
Small guage wire (#16 type TFF -for flexibility) tied to the load side of the bucket fuses or with a separate fuse block for larger starters.

This could aid in troubleshooting as well with the door closed. I think I would probably make it procedure to open the the door after testing to get a visual verification that the switch opened.
Click to expand...

I would not accept the fuse idea in the verification circuit as they could be open.
 
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