[mikelp1951]

Can I use a 200Amp outside disconnect to feed a 100Amp main panel box?

[hfcarson]

Maybe... is the outside disconnect a "fused" switch? It is existing?
How about the 100 amp panel? Is this for a dwelling?
Can you explain a bit why you are trying to use this setup?

[Brsmith135]

Yes. You can use this. If it has fuses rated at 100 amp. Or if it is fed with a 100 amp breaker

[stanfortyman]

A 100A breaker will not fit in a 200A disconnect.

mikelp1951, can you provide us with some more info, or even a pic of the disconnect?

[Brsmith135]

A breaker will not fit in a disconnect at all. If the 100 amp breaker is feeding the line side of the disconnect it meets code. Generally 125 amp fuses are the smallest fuses that will fit in a 200 amp disconnect.

[stanfortyman]

A breaker will not fit in a disconnect at all.

Sorry. By disconnect I meant breaker enclosure. If I meant fusible disconnect I would have said so.

If the 100 amp breaker is feeding the line side of the disconnect it meets code.

Why in the world would someone feed from a 100A disconnect into a 200A disconnect? :confused: :rolleyes:

Generally 125 amp fuses are the smallest fuses that will fit in a 200 amp disconnect.

There are also fuse reducers that will allow 100A (or smaller) fuses in a 200A fusible disconnect.