Where does the fuse go?

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Dale Hayes

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Non-fusible disconnects can obtain a higher SCCR rating when protected with the appropriate fuses. For example: A 1200Amp non-fusible disconnect switch can be rated at 100kA SCCR when used in conjunction with a 1200amp type 'L' fuse. Where does the fuse go? Does the fuse connect to the line tabs on the non-fusible disconnect switch? Is the fuse mounted to separate fuseblocks? Is there any standard procedure for fusing a non-fusible disconnect? Unfortunately, the manufacturers of the fuse and switch show nothing about assembling the combination.

Con"fused" in Missouri.
 
Dale Hayes said:
Non-fusible disconnects can obtain a higher SCCR rating when protected with the appropriate fuses. For example: A 1200Amp non-fusible disconnect switch can be rated at 100kA SCCR when used in conjunction with a 1200amp type 'L' fuse. Where does the fuse go? Does the fuse connect to the line tabs on the non-fusible disconnect switch? Is the fuse mounted to separate fuseblocks? Is there any standard procedure for fusing a non-fusible disconnect? Unfortunately, the manufacturers of the fuse and switch show nothing about assembling the combination.

Con"fused" in Missouri.
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The fuse would be located ahead of the subject non-fuse disconnect. A good example would be the non-fuse disconnect could not be used as a service disconnect on a service with an AIC >10k, but it could be used as and equipment disconnect down steam from a the proper fuse in a distribution board.
 
The fuses are installed anywhere upstream of the disconnect.
... Like in an MCC, or panelboard, or a fuseblock in an enclosure.

Jm
 
Dale Hayes said:
Non-fusible disconnects can obtain a higher SCCR rating when protected with the appropriate fuses. For example: A 1200Amp non-fusible disconnect switch can be rated at 100kA SCCR when used in conjunction with a 1200amp type 'L' fuse. Where does the fuse go? Does the fuse connect to the line tabs on the non-fusible disconnect switch? Is the fuse mounted to separate fuseblocks? Is there any standard procedure for fusing a non-fusible disconnect? Unfortunately, the manufacturers of the fuse and switch show nothing about assembling the combination.

Con"fused" in Missouri.
Click to expand...

The fuses would go in a fusible disconnect upstream of the unfused disconnect.
 
Dale Hayes said:
Where does the fuse go?
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Obviously, you mean physically, not electrically. As suggested above, the best place for the fuses is the origination of the feeder. If it's a tap, you'll have to add an enclosure for the fuses, unless the switch in question has room for them.

Con"fused" in Missouri.
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Cute. :)
 
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