De-Energize

A

Alwayslearningelec

Senior Member
Location
NJ
Occupation
Estimator
Hello. So have to replace the 100A disconnect switch tied into the last cubicle of this switchboard. Assume right way to do it is to shutdown this board.

Looks like drawout breakers feeding this board.....actually looks like a few breakers feeding this board, not sure how that could be.
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I would expect to see some kind of kirk key or other interlock mechanism higher up on the drawing. From the portion provided, there are potentially eight breakers and (at least) four different upstream panels all paralleled as inputs to that bus with no cross- or back-feed prevention.
 
Alwayslearningelec said:
Assume right way to do it is to shutdown this board.
Click to expand...
Looks like it... the added detail, to me, appears to be a combination of on-site solar- and fuel cell-based generation, together with redundant parallel feeds off the (probably diesel) generator, all three of which likely have a central paralleling controller. Odd that they'd do all that work to ensure the thing never loses power, only to still be forced into shutting the whole thing down to replace a disconnect. If you're able, I'd ask if they have disconnects on the sections that aren't marked here, just to be sure there isn't a way to isolate the cubicle you're working in from the rest of the bus.
 
The line side of that disconnect is connected to the conductors on the line side of the service disconnect. The service will have to be disconnected by the utility to do that work.
 
The other breakers are indeed all draw-out, but you are wanting to connect to the tap section, so that will require either for the entire board to be de-energized, or for you to apply for and receive a hot work permit from the site owner/manager in accordance with their safe electrical work practices documentation.
 
The arc-flash energy on that board must be huge.
Hopefully all the important loads are connected to the generators so disconnecting this board just causes loads to transfer. It looks like the disconnect you're replacing is for the fire pump and alarm. Unless one side of that gear can be disconnected, I don't see how this can be safe without a full gear shutdown.
 
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