# Mixing 12/2 and 14/2 house wiring

Can I run 12/2 wiring from a load center to a junction box, then use 14/2 for branch circuits?

• Never a good idea to do this. Maybe if you ran out of the one size of wire. – JACK Jan 26 at 15:10
• Why are you wanting to do this to begin with? – ThreePhaseEel Jan 26 at 15:50
• The only reason I would consider this is to minimize voltage drop for a long run on a lighting-only circuit. Doing lighting circuits entirely in 12 awg is unnecessary in the age of LED lighting while increasing cost (more expensive wire, larger junction boxes) and 14 awg is much easier to work with at the fixtures and switch boxes. Definitely make sure to leave a note at the panel though. – statueuphemism Jan 26 at 17:02
• @ statueuphemism Why lighting only? It would seem your LED reasoning reduces the need to increase size to compensate for voltage drop, while receptacles would be prone to overload. – NoSparksPlease Jan 26 at 17:17
• I seriously doubt you'll have voltage drop problems with #14 AWG. Just how many miles is this run you're talking about? – JACK Jan 26 at 18:37

You can, but only if the breaker is 15 amps, and it creates possible confusion for someone who looks at the breaker box and thinks "huh, that's 12GA, I can change that to a 20A breaker." So you might want to leave that person a note in the box.

## You may be miscalculating voltage drop

The first rule of voltage drop is: Calculate voltage drop based on the actual, normal circuit load, not breaker trip. Suppose you have 7A of lighting, but only 3A will be realistically on at one time, on a 15A trip. What number do you punch into the voltage drop calc?