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I'm a beginner adding a 220V 40A circuit via exposed conduit for my new induction cooktop. Does this plan look reasonable?

  1. Under counter metal junction box grounded and mounted to back of cabinet. Cooktop whip will connect to this (hot-hot-ground).
  2. LFNC-B conduit running exposed inside cabinets behind top row of drawers (3" clearance). Could use FMC but easier for me to cut non-metallic than FMC. Mostly straight run but not perfectly straight enough to make EMT easy.
  3. LFNC-B dives through drywall into space where drainage plumbing is (with clean out, etc.) then out through drywall again (less than 3') into the garage. LFNC-B connects to back KO of drywall mounted metal junction box. No splice here but figure a junction box will hide the drywall hole better than a pull elbow and planning to transition to EMT in the garage so need a junction box.
  4. EMT run with 2 pull elbows to get directly above main service panel, which is drywall finished. EMT terminates at side KO of drywall mounted junction box. Will use <12" of remaining LFNC-B to dive into drywall via back KO and into service panel. Junction box will be grounded which should ground the EMT run and the other garage junction box as well.
  5. Plan to run 8AWG copper THHN x4 (55A ampacity) in 3/4" conduit based on the fill tables. Don't need neutral now, but might as well have it in case it is needed later. May use 6AWG to "future-proof." Will use 40A double pole breaker.

Entire run is about 40', roughly half EMT in garage and half LFNC-B in the kitchen. Will use appropriate conduit-specific fittings/clamps at each junction box.

Any thoughts/feedback/warnings much appreciated.

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EDIT #1:

After opening up my main service panel, it looks like the behind-drywall run to the first wall-mounted junction box will need to be 6/3 NM-B (which maintains 50A capacity). Not enough room for a conduit/coupling as I had planned. Will use correct bushing (at panel) and cable clamp at junction box, and splice to THHN in the junction box. Any issues?

Also, the panel is oriented service-side down, load-side up. Using a bottom KO for my 220V circuit would make my exposed conduit run much shorter. Is that OK or does code call for keeping load and service sides strictly separate? (One load to the water heater is already routed down as you can see.)

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Yeah, that sounds fine. Feel free to use sweeps rather than pull elbows where convenient. Conduit must be assembled complete before any wires are pulled, so it has to be built pullable.

Your ground must be green or bare. (#10 will suffice). Neutral must be white or gray. Hots can be any other color, it's fine for both hots to be the same color.

Plan to run 8AWG copper THHN x4 (55A ampacity) in 3/4" conduit based on the fill tables. Don't need neutral now, but might as well have it in case it is needed later. May use 6AWG to "future-proof."

#8 is 50A capacity (the 90C column of the table is not available in residential because no residential-priced equipment is ready for 90C). However nobody makes ranges bigger than that, so you're not likely to need more ever. If you had separates and they totaled >50A you might add an additional pair of #10 and done.

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  • Separates on the same circuit count as one range load anyway Mar 24, 2023 at 3:31
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    I know I /can/ make both the hots red in a 240V circuit, but it still looks weird when I do it.
    – KMJ
    Mar 24, 2023 at 6:19
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    @KMJ ProTip™: _ on both sides makes _italics_ turn into italics.
    – FreeMan
    Mar 24, 2023 at 15:44
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    @KMJ it'll look less weird when you have two 240V circuits of the same wire size in that pipe. Then you'll be happy one circuit is black-black and the other is red-red. Mar 24, 2023 at 18:29
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    @sx64 The ground pigtail would need to be #10. There's no height restriction for junction boxes. I have some I need a boom lift to get to. Mar 24, 2023 at 22:32

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