1200 amp DS

[hec480v]

Hello and thank you

Can an existing 1200 amp fused disconnect be fused down to 400amps and used to feed a 400amp CB panel. If yes or no where can I find it in the NEC. The panel is located aproximitly 484ft away, I'll like to explain it to the client and back it up with any code issues if any.

 

[skeshesh]

I would think it depends on the product. You will need the appropriate fuse clip, etc. to assemble it. I'm not sure if a 400A fuse will fit in a 1200A disconnect; I would think the frame sizes are pretty different so the manufacturer doesnt provide any options for installing a fuse that small. At the same time I've never really installed a disconnect switch, maybe one of our experienced, hands-on guys on the forum (and there's plenty) will provide you with a better answer.
As far as code violation I don't see one. I can't say I provide a reference that says you definitly can do it but I don't think there's any rules preventing it.

 

[Jraef]

It depends on the fuse holder. If your switch has holders for Class L fuses, as many 1200A fused disconnects do, then I don't think you can get Class L fuses less than 600A. Newer switches sometimes allow you to move the lower base up so that you can use Class T fuses and they are available down to 400A. Wire sizes are also an issue, but I just looked at a couple in catalogs I have and the cable lugs go down to 1/0, so no problem there either.

As to the code, there is no reference I can think of probably because there is nothing wrong with doing it. The 1200A rating of the switch is a maximum rating. You can put a 1A fuse in there if you are so inclined, you just can't put in a 1201A fuse.

 

[petersonra]

Hello and thank you

Can an existing 1200 amp fused disconnect be fused down to 400amps and used to feed a 400amp CB panel. If yes or no where can I find it in the NEC. The panel is located aproximitly 484ft away, I'll like to explain it to the client and back it up with any code issues if any.

some types of fuses have adapters you can buy to fit a smaller sized fuse in a larger fuseholder.

i don't see a problem with doing so.