I have a 200-amp main panel.

I want to feed another panel, which will have two 50-amp breakers (for air conditioning and stove) and one 30-amp breaker for the clothes dryer. The sub panel will be about 30 feet away, at the A/C unit. The dryer and stove are about 30 feet further.

I have 1-inch conduit. What size wire should I run between the panels?

  • 1
    Why run all these high-current appliances off a sub panel? The feeder would need to be almost as big as the main. – Ian Jul 17 '16 at 23:28
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    Makes sense, fewer larger wires are cheaper than more smaller ones. – Harper - Reinstate Monica Jul 17 '16 at 23:34
  • But you have the additional expense and labor of a sub panel. I'm not convinced it would be cheaper. Furthermore, four 1 or 2 AWG conductors won't fit through 1 in conduit. – Ian Jul 17 '16 at 23:46
  • What are the nameplate wattage/amperage ratings on your dryer, stove, and AC? – ThreePhaseEel Jul 18 '16 at 0:17
  • Is this conduit already installed, or something you're putting in? – ThreePhaseEel Jul 18 '16 at 0:18

You are undone. You have 130A of loads which are quite conceivably on at the same time, so you need #1 or #0 wire. I would err on the high side, honestly. I'd even think about 2/0.

You also need four conductors unless the conduit is all-metal in which case you need three.

1" conduit will only support #4 wire (85A) in four conductors... Or #2 wire (115A) in three conductors**. And even then, you're at conduit limits, which makes for a rather miserable pull... for which you'll need special tools and skill not lending itself to DIY.

If this is a DIY, then dollar for dollar, it'd be far cheaper to install 2" conduit so you can easily and legally pull what you need.

** 130A is allowed with 90C terminations, but good luck finding those... and you'd really want to run that by your local inspector before buying anything. I mean you do expect to occasionally run the wire at actual full capacity, literally, people would burn their fingers if they touched the conduit. Seems a bit crazy.

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