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Old 15th September 2005
Lives for gear
brianroth's Avatar

Geeeez...there is a LOT of misunderstanding about wire size and the NEC (National Electric Code).

NEC specifies the maximum size breaker that can be used for a given wire gauge. The whole idea is PROTECTION of the downstream wire.

15 Amps is the MAXIMUM size breaker allowed to PROTECT a run of 14 gauge wire. 20 Amp breakers are allowed for 12 gauge wire. Those specs are for wire in conduit or "romex".

If you swap in a 20 Amp breaker in place of a 15 Amp breaker that is PROTECTING a run of 14 gauge wire, and something goes awry, causing the wire to overheat and start a fire, you will likely have no recourse when your insurance company rejects your fire claim.

While it's probably true (I need to find the resistance per foot for 14 and 12 gauge wire to verify my hunch) that a 20 foot run of 14 will have less *voltage drop* than a 100 foot run of 12, that has NOTHING to do with the safety aspects. The IR losses (dissipated as heat) are distributed along the length of the longer wire.

Don't play fast and loose with AC mains circuits..