70E & Fuse Replacement in Fused Disconnect

[doyuski]

In the energized state the Fused Switch has an Arc Flash rating of "Dangerous". My question is If the fusibleswitch is placed in the OFF position, can the door to the Fusible Switch beopened and the fuses replaced without turning off power to the entire busway? All exposed parts within the FS are behind a physical barrier. It seems that since there are no exposed parts within the Fusible Switch when theswitch is in the OFF position this would be acceptable. Or doesthe Busway need to be de-energized to consider the Fusible Switch Electricallysafe to replace the fuses or attach field conductors? Any direction on where I can find some documentation to validate that fusible disconnects are in an electrically safe condition when they are switched to the OFF position would be appreciated.

 

[jim dungar]

This is not explicitely addressed in NFPA 70E. It needs to be covered under your employer's Electrical Safe Work Practices Program.

You have two things to consider:
PPE to protect against the 480V shock hazard, and
PPE to required by being within the Arc Flash Protection boundary.

It is likely you could build a case for perfoming the work, but it is all but impossible to escape the Arc Flash issue. For example, suppose the busway to disconnect jaws fail while you are jostling the switch.

 

[wbdvt]

In the energized state the Fused Switch has an Arc Flash rating of "Dangerous". My question is If the fusibleswitch is placed in the OFF position, can the door to the Fusible Switch beopened and the fuses replaced without turning off power to the entire busway? All exposed parts within the FS are behind a physical barrier. It seems that since there are no exposed parts within the Fusible Switch when theswitch is in the OFF position this would be acceptable. Or doesthe Busway need to be de-energized to consider the Fusible Switch Electricallysafe to replace the fuses or attach field conductors? Any direction on where I can find some documentation to validate that fusible disconnects are in an electrically safe condition when they are switched to the OFF position would be appreciated.

The switch is labeled Dangerous therefore there is no PPE that is suitable for interacting with that switch, which includes operating it, while it is energized at the working distance specified in the study. Even if the switch was operated with a hot stick so that one was outside the Dangerous zone, the switch would still be energized and considered Dangerous for arc flash hazard, since one would still be inside the arc flash boundary. The switch must be de-energized completely to work on.

Since this sounds like it is bus plug fused disconnect switch, I do hope that bus plugs are not being inserted into the bus duct while it is energized. It sounds like the bus duct is Dangerous for arc flash hazard. It would be interesting to see, if the bus duct is fed by a circuit breaker, what the instantaneous setting is. Many times I have found that, where possible, reducing the instantaneous setting will greatly reduce the arc flash hazard. Hopefully the study looked at that possibility.