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 Post subject: Approach Boundaries for Control Cabinets
PostPosted: Tue Feb 23, 2010 6:55 am 
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Consider a PLC/Control cabinet with 120VAC L-N so the "nominal system voltage" is 208v. From the table the LAB is 3'6" and the RAB and PAB are non contact. If all the conductors are insulated and there are no "exposed circuit Parts", that is all the terminals and PLC connections are finger safe. Looking at the definition of exposed then there is nothing exposed. So then is the LAB=0 and not a factor and the only thing to be considered is the RAB and PHB if one wants to work on something in the cabinet. Looking for advice and others experience.


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PostPosted: Tue Feb 23, 2010 7:32 am 
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Interpretation

Give OSHA a call and ask if "finger safe" is considered exposed. Especially if you have tools in your hand. See what the interpretation is.


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PostPosted: Wed Feb 24, 2010 7:30 am 
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Finger Safe

John Perrotti wrote:
Give OSHA a call and ask if "finger safe" is considered exposed. Especially if you have tools in your hand. See what the interpretation is.


That is not the question being asked. What if it was a junction box with no terminals? FYI, OSHA will not answer my phone calls.


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PostPosted: Wed Feb 24, 2010 8:26 am 
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Finger Safe

The point I am trying to make is even if something is considered finger safe, it is not necessarily guarded or insulated from contact.


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PostPosted: Wed Feb 24, 2010 8:34 am 
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John Perrotti wrote:
The point I am trying to make is even if something is considered finger safe, it is not necessarily guarded or insulated from contact.


Agreed, what do you think about the rest of the question?


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PostPosted: Wed Feb 24, 2010 11:23 am 
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Work

Define for me work? Are you just visually checking something, or are you bringing tools into the LAB? I am still assuming the LAB is 42" here.


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PostPosted: Wed Feb 24, 2010 6:19 pm 
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Something that is 'finger save' is also not exposed. So you would not be doing 'live work' if you were in the cabinet doing mAmp checks or just observing function lites.


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PostPosted: Thu Feb 25, 2010 10:36 am 
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Working On

John Perrotti wrote:
Define for me work? Are you just visually checking something, or are you bringing tools into the LAB? I am still assuming the LAB is 42" here.


Here is the definition of working on:Working On (energized electrical conductors or circuit
parts). Coming in contact with energized electrical conductors
or circuit parts with the hands, feet, or other body parts,
with tools, probes, or with test equipment, regardless of the
personal protective equipment a person is wearing. There
are two categories of “working on”: Diagnostic (testing)
is taking readings or measurements of electrical equipment
with approved test equipment that does not require
making any physical change to the equipment; repair is
any physical alteration of electrical equipment (such as
making or tightening connections, removing or replacing
components, etc.).

So can I work on someting else in the cabinet that is not energized?
For example changing a light fixture.


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PostPosted: Thu Feb 25, 2010 1:38 pm 
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If the cabinet is energized, then the cabinet is energized. It shouldn't matter whether a specific component in the cabinet is energized or not.


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PostPosted: Thu Feb 25, 2010 2:52 pm 
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Sparkytrician wrote:
If the cabinet is energized, then the cabinet is energized. It shouldn't matter whether a specific component in the cabinet is energized or not.


But could I work on the light or someting else that is not energized, provided that I do not cross the RAB and PHB?


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PostPosted: Wed Mar 24, 2010 9:45 am 
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Boundaries

Exposed has a specific meaning. You must be able to come into inadvertent contact with the energized component for it to be exposed. If there is no exposed energized equipment, there is typically no boundary requirements. Fingersafe may or may not be considered non-exposed. Your typical disconnect covers can be snap on finger-safe covers (exposed) or screw on finger-safe covers (non-exposed).

Also, any work you do inside the LAB with exposed energized equipment requires that the proper PPE be worn regardless if the equipment being serviced is energized. Where it becomes important is the Energized Work Permit and Job Briefing. If you are not working inside the Prohibitive boundary or you are performing one of the approved tasks (testing, visual inspection, etc.), you not need to fill out the EWP. If you are working in the Prohibitive boundary or you are changing the state of energized equipment, you will an EWP. On there you will need to state the justification for doing energized work. There are only 2 justifications: 1)it increases the hazards to shut the power off 2)it is infeasible to shut the power off due to design or process.


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PostPosted: Wed Mar 24, 2010 4:45 pm 
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If you open a wireway and all that is inside is insulated wires, this is NOT live work. There has to be exposed conductors, or the switching of significant energy (switchgear) to invoke the arc flash regs.


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