"50 Volts or less" question:

Status
Not open for further replies.
R

rproskey

Member
According to NFPA70e, work on anything above 50 volts requires the use of the proper PPE. My hypopthetical question is: We have a 480VAC control panel for a machine. We shut off the main disconnect and lock it out. OK- now the power is off and locked out, is it OK to work inside the panel without PPE on even though there is still 480VAC at the top of the disconnect... or is PPE still required (besides safety glasses, ear plugs)?

Thanks!
 
billsnuff

billsnuff

Senior Member
Location
East of 480sparky
OK- now the power is off and locked out
Click to expand...

If this were true, PPE may not be required

there is still 480VAC at the top of the disconnect...
Click to expand...

Obviously, the first statement, above, is not true :cool:


I have had and in some cases still have the same situation. I have used Hubble 3 ph lock-out switches mounted externally, to mitigate the issue, where possible. 80A max, I think. Still need PPE to conduct Live-Dead-Live test.
 
R

rproskey

Member
Even though the disconnect is off, there still would be voltage at the top, correct? So are you suggesting that the power feeding the disconnect needs to be killed also in order to not wear PPE in the panel?

Thanks!
 
billsnuff

billsnuff

Senior Member
Location
East of 480sparky
devil's advocate

devil's advocate

If you have to wear the appropriate PPE to verify the absence of voltage, why would it be OK to work in a panel with live 480vac 3ph present and not wear PPE? :cool:
 
Last edited:
R

rproskey

Member
Good point.

Sorry I was not clear. I was thinking of a covered disconnect- the type where the line side of the disconnect is covered. No exposed hot lugs. What about then?

Thanks!
 
zog

zog

Senior Member
Location
Charlotte, NC
rproskey said:
Good point.

Sorry I was not clear. I was thinking of a covered disconnect- the type where the line side of the disconnect is covered. No exposed hot lugs. What about then?

Thanks!
Click to expand...

Gaurding of the live parts removes the requirement for shock protection PPE but you still have an arc flash hazard and need arc flash PPE.
 
Jraef

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
People like Hoffman are addressing this now with new enclosure designs that have isolated disconnect compartments. Saginaw has a nice little package that is just an isolating compartment that goes around the disconnect switch itself that can be added to existing enclosures.
 
zog

zog

Senior Member
Location
Charlotte, NC
Jraef said:
People like Hoffman are addressing this now with new enclosure designs that have isolated disconnect compartments. Saginaw has a nice little package that is just an isolating compartment that goes around the disconnect switch itself that can be added to existing enclosures.
Click to expand...

Yes but still requires arc flash PPE, even if the live parts are not exposed, that was a major change to the 2009 70E clarifications. I assume at some point there will be an ANSI standard for an "arc resistant" design for a hoffman type box like there is for metal clad switchgear, but until then......
 
RoberteFuhr

RoberteFuhr

Member
Location
Covington, WA.
No, it is not ok to work in this panel if the top of the main disconnect switch is still hot without PPE. The only possible way would be if you put a barrier blanket or cover on the top that would prevent shock and arc flash hazard.
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Bob,
Are there blankets that can provide protection from the arc flash/blast? I thought the blankets were only for shock protection.
 
Status
Not open for further replies.
Top