I running 2-2-2-4 wire from a 100amp breaker from the main panel. to a 125amp sub panel. it's going to be a 105ft from main panel to sub panel. Just making sure my wire is right for the job

  • Have you calculated the voltage drop yet? cirris.com/learning-center/calculators/… lets you convert a wire gauge and length (such as 220 feet for this circuit) to a resistance.
    – Jasper
    Jan 5, 2018 at 5:46
  • 1
    Copper or aluminium?
    – Tester101
    Jan 5, 2018 at 15:45
  • It's a living room and a full bath I know a computer and TV pluged in living room and I have a 220 AC/heater unit that plugs in. And 9 can lights with LED bulbs I think are 13w a piece. Gfci plug in the bath room that's on its on breaker same with the hot water heater it's on its on 20A breaker
    – Mikey
    Feb 6, 2018 at 18:39

1 Answer 1


If your wire is copper then you have properly upsized for a long run and you should be just fine if you are not fully loading the circuit.

The voltage drop calculator here recommends #1 at 100 amps and #3 at 80 amps. So, #2 should be fine up to 90 amps or so. There are many calculators like this to be found on the interwebs and the 3% voltage drop recommended by the National Electrical Code is just that, a recommendation. It is not found anywhere in the text of the Code and is therefore unenforceable. However, if you want your equipment to work properly then it is good advice to heed.

I seriously doubt you will ever have more than 80 amps on the circuit unless you are an indoor farmer or cryptocurrency miner. In that case you should go larger on the wire and panel.

Good luck!

  • 3% & 5% is mentioned in code as an informational note after 215.2.b as far as not being enforceable I have had local AHJ requirements that did enforce localy.
    – Ed Beal
    Jan 5, 2018 at 14:09
  • Your voltage drop calcs should be based on your daily expected use of the circuit, not the point at which the breaker will trip. Jan 5, 2018 at 20:03
  • Just found out it's aluminum 2-2-2-4 so I'm just going with a 70A breaker thanks all man this a great place to get answers
    – Mikey
    Feb 6, 2018 at 18:25

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