Wire reduction

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As far as I know. There are many reasons why this might be done. A long run might use #8 to minimize voltage drop, but use #12 at the end of the run to work with the devices. Or a larger amperage device might be repurposed for a 20A device and just reuse the existing #8 wire, again usually with #12 at the device to make it workable. I've actually done this one.

There might be some steps taken to make it clear to someone else not to swap out the breaker later when they see the bigger wire.
 
As is always the case, the devil is in the details.

As has been noted above, using a larger than minimum conductor and changing between minimum and larger conductors in a single circuit is done for many reasons and quite frequently.

You may encounter various limits on doing this.

The big issue that you might encounter is if you are using _cables_ rather than individual wires. #8 NM cable commonly has a #10 EGC (ground) wire. But for 20A circuits, if you increase the size of the circuit conductors you must also increase the size of the EGC by the same amount. So you can't legally use #8 NM on a 20A circuit, even though it would be perfectly kosher on a 40A circuit.

-Jon
 
winnie said:
As is always the case, the devil is in the details.

As has been noted above, using a larger than minimum conductor and changing between minimum and larger conductors in a single circuit is done for many reasons and quite frequently.

You may encounter various limits on doing this.

The big issue that you might encounter is if you are using _cables_ rather than individual wires. #8 NM cable commonly has a #10 EGC (ground) wire. But for 20A circuits, if you increase the size of the circuit conductors you must also increase the size of the EGC by the same amount. So you can't legally use #8 NM on a 20A circuit, even though it would be perfectly kosher on a 40A circuit.

-Jon
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Good point. :cool:
 
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