Shutting Down Power To Main Switchboard

[Davebones]

We have a 4000 amp Sq D Power Style Switchboard 480 V . This is 3 sections tied together . The first section has a 4000 amp bolt-loc switch which feeds the 2 sections next to it . We are needing to install a 400 amp breaker and pull new wire and tie in . The question is if we open the bolt-loc that feeds the 2 sections that have breakers in them is this considered as being de-energized ? There would still be power to the line side of the bolt-loc . I would prefer we see about getting the main transformer that feeds this whole switchboard shut-off . The contractor doing the work thinks it's ok if only the main bolt-loc switch is opened . We just got the arc flash study done and the incident energy is listed at 94 cal/cm . Wondering how other people would deal with this ...

 

[jim dungar]

We have a 4000 amp Sq D Power Style Switchboard 480 V . This is 3 sections tied together . The first section has a 4000 amp bolt-loc switch which feeds the 2 sections next to it . We are needing to install a 400 amp breaker and pull new wire and tie in . The question is if we open the bolt-loc that feeds the 2 sections that have breakers in them is this considered as being de-energized ? There would still be power to the line side of the bolt-loc . I would prefer we see about getting the main transformer that feeds this whole switchboard shut-off . The contractor doing the work thinks it's ok if only the main bolt-loc switch is opened . We just got the arc flash study done and the incident energy is listed at 94 cal/cm . Wondering how other people would deal with this ...

Most service companies I know of, would consider this as de-energized work. However, you are performing this work within the arc flash boundary of the energized main lugs, therefore you would still need PPE sufficient for your 94cal/cm?. Of course you may be able to reduce this value, based on the distance from the energized line side to the point where you are working.

I would have more issues with your operation of the bolted-pressure switch. Without proper maintenance (e.g. servicing every 3 years) this style device has been known to have operational failures in the 50% range.

 

[WorkSafe]

I'm not to familiar with large equipment like this, but if there are exposed energized parts where an employee, tool, or the while pull, potentially could come in contact with, then you would need to denergize the entire unit.