Learned the hard way
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| Circuit Still Energized? https://brainfiller.com/arcflashforum/viewtopic.php?f=33&t=2730 |
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| Author: | Jim Phillips (brainfiller) [ Sun Apr 21, 2013 12:36 pm ] |
| Post subject: | Circuit Still Energized? |
When establishing an electrically Safe Work Condition many steps are required which include testing for absence of voltage and determining all possible sources of power. This week’s question: Have you ever thought that you completely de-energized a circuit and found it was still live - either by voltage testing or other “unexpected” means?
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| Author: | C. Marsh [ Sun Apr 21, 2013 7:27 pm ] |
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Learned the hard way
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| Author: | tish53 [ Mon Apr 22, 2013 7:28 am ] |
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I answered yes but only if we had taken some short cuts. If I followed proper accepted procedures for testing before touching then I would answer no. Mostly in disconnect swiches where one phase holds in or a motor starter with one phase welded contacts, if we didn't test it could have been a bad situation. |
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| Author: | Larry Stutts [ Mon Apr 22, 2013 7:39 am ] |
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tish53 wrote: I answered yes but only if we had taken some short cuts. If I followed proper accepted procedures for testing before touching then I would answer no. Mostly in disconnect swiches where one phase holds in or a motor starter with one phase welded contacts, if we didn't test it could have been a bad situation. Or is the case of a 'neutral shock'? Ive seen that before as well where someone has disconnected something, or though they did. Power was still connected to the 'hot' side somewhere (either through an alternative power source - or MORE likely they were working hot), and then discover the circuit is still powered when they try to connect the neutral. I know some plant maintenence people who equate neutral and ground as the same thing. They forget that neutral is current carrying and ground is not supposed to be, and - more importantly - if you put yourself in series with the neutral line of a circuit you will get shocked just like if you touch the 'hot' line of a circuit. |
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| Author: | A King [ Mon Apr 22, 2013 7:48 am ] |
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I've seen a couple 480 V, 3 phase disconnects (knife-switch) where not all three legs opened after operating the handle to to the Off position. |
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| Author: | Don Jones [ Mon Apr 22, 2013 11:13 am ] |
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This happened just a couple of weeks ago. Good thing I checked the voltage first - what a surprise! |
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| Author: | KEC [ Mon Apr 22, 2013 3:40 pm ] |
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I turned off a 400amp 208v CB and one of the phases did not open. I was always told not to trust my life to the inductance testers but when I ran it across the phases it identified one leg was still energized. The CB was new and defective, we ended up replacing it. |
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