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I'm planning to add 2 new circuits, one for water heater (assuming my load calculations are correct) and one for dryer. The one for the dryer replaces an existing unsafe wiring.

Since I plan on running 10/2 cable for the water heater I might as well run another 10/3 cable for the dryer in the same conduit and install a new NEMA 14-30R.

Do I need a GFCI breaker for the dryer circuit? For the water heater I need a regular breaker right? See photos of the panels.

What conduit do you recommend? PVC, EMT, or RMC? What size to be able to fit both cables? I don't need any junction boxes anywhere right? I'm thinking LB conduit body above the subpanel, and type-T conduit body at the top left where the two runs will split.

Is a water heater disconnect needed? Is a flexible conduit needed from the disconnect box or the type-T conduit body or can I just have the cable connected on top of the water heater?

I'm in Sunnyvale, CA. The water heater is in the corner on the left behind the fridge.

EDIT: After more research and the answer and comments below I'm thinking of going with boxes instead of conduit bodies:

  • Instal a metal box by the ceiling (top right of my photo).
  • Fish 2 NM cables (10/2 and 10/3) vertically to the panel (unsupported cables per NEC 334.30(B)).
  • Install another box by the ceiling (top left of my photo).
  • Run a 1/2" EMT with 5 10 AWG THHN horizontally between the two boxes.
  • Connect a flexible conduit for the water heater in the top left box
  • Run a vertical 1/2" EMT with 3 10 AWG to another box that will have the dryer outlet.
  • Securely fasten the EMT within 3 ft of each box and at least every 10 ft.
  • Add a GFCI breaker for the dryer circuit but not for the water heater since it will be hardwired.
  • Skip the disconnect for the water heater since the panel is within sight (about 12 feet away).
  • Ground pigtail all three boxes. Splice the two NM cables and ground pigtail to the top right box.
  • Add a ground wire in the flexible conduit to the water heater and splice it with the ground pigtail in the box.
  • The 5 wires in the conduit will be spliced only in the top right box with the NM cables and they will terminate to the water heater and dryer. i.e. they won't be spliced in the top left box.

diagram

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  • IIRC, you need a pull point every 180 degrees (max) of bends in a conduit. It doesn't need to be a junction box, but it does need to provide access. See Do separate pieces of EMT conduit qualify as "pull points"?.
    – HABO
    May 25, 2023 at 12:27
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    There is only one 90 degree bend at the top right. The one on the top left will be a type-T conduit body. The line on top is a straight line. It appears like that on the photo because it was shot as panorama.
    – user162793
    May 25, 2023 at 12:39
  • You have a whole lot of questions in one post here. While they're loosely related, that violates site policy. Please revise to narrow the scope of your post. See How to Ask and take the tour. It's fine to post a series of questions.
    – isherwood
    May 25, 2023 at 12:50
  • GFCI needed for dryer receptacle since 210.8 now includes laundry area. Not needed if hardwired, but disconnect means would be required. Both water heater and dryer are subject to 422.31 requiring within site of disconnect or breaker, or permanent means in place to lock off breaker. May 25, 2023 at 17:51

1 Answer 1

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If you try to run two cables in conduit you'll need conduit the size of a sewer pipe (roughly) since cables are figured as "round of the largest dimension" and due to jamming 2 conductor fill is a whopping 31% (or less.)

5 (or 6) wires will fit in a much more reasonably sized conduit at 40% (or less) fill based on the area of the individual wires.

The ground wire is not needed at all if you use non-flexible metallic conduit, and can be shared by both circuits in the conduit if you use flexible metallic or any non-conductive type of conduit.

So:

  • 5 10 AWG in 1/2" or larger EMT.
  • 5 10 AWG in 1/2" or larger IMC.
  • 5 10 AWG in 1/2" or larger RMC.
  • 6 10 AWG in 3/4" or larger FMC
  • 6 10 AWG in 3/4" or larger PVC-80 (can't use PVC-40 as it's exposed to damage unless you are putting in the wall, and then you'd probably want 3/4" ENT, not PVC-40)
  • 6 10 AWG in 3/4" or larger ENT
  • 6 10 AWG in 3/4" or larger LFNC (not that I'd recommend that - miserable stuff to pull wires in, use only where you need the flex and as short as possible. You don't need the flex. If you want flex so you don't have to bend, use FMC or ENT, it pulls like a dream, comparatively.)
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  • Can I share ground between a GFCI and non GFCI circuit? EMT seems much cheaper. If I go with 5 10 AWG in 1/2" EMT, how do I ground the conduit? I will need a junction boxes and not conduit bodies, right? I'm thinking a junction box above the panels to attach the ground wire. No splicing in the box. Another box again without any splicing to the top left to route the 3 wires to the dryer outlet and the 2 wires plus a new ground to the water heater via a flexible conduit. Or is there a way to ground conduit bodies?
    – user162793
    May 25, 2023 at 19:25
  • Complete, correctly connected non-flex metallic conduit is a ground conductor - so you don't need a grounding wire in it (that's why 5, not 6 wires - two hots for the charger, plus 2 hots and 1 neutral for the dryer, conduit itself as ground) and then you connect a pigtail to the grounding screw hole on the metallic box where the device is. The correctly tightened metallic connectors (and removal of paint if you don't use ones that are designed to break through the paint themselves) connects the conduit to the grounded panel or sub-panel.
    – Ecnerwal
    May 26, 2023 at 1:31
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    Sharing the ground is normal and unremarkable. GFCIs do not look at ground. One suitable for a 240V dryer compares current on the two hots and neutral for the dryer. If they don't add up, that's a ground fault - no need to actually look at ground, and GFCIs will work on ungrounded circuits because that's how they work.
    – Ecnerwal
    May 26, 2023 at 1:35
  • I edited my question with my plan. Please let me know if that looks good.
    – user162793
    May 26, 2023 at 18:32
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    You need white or gray for the neutral wire at this wire size. The hots can be all one color and tape marked, or two colors to make it easier. If using two colors, use e.g. red for both hots of one circuit, black for both hots of the other. Or pink, blue, orange... Your revised plan appears workable.
    – Ecnerwal
    May 26, 2023 at 21:33

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