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We have a detached garage approx 95ft away from the main house and we are looking to run a 240v circuit there.

Currently we have Romex wire running straight into the ground. (This is how it was when we moved into the house. I have attached a picture below.) This feeds basic outlets and the garage door. We would like to run either straight to a circuit, or a small sub-panel to provide for the 110v (outlets and garage door, and 240v - EV)

My plan is the following:

  • Trench down 18" and run 1" PVC 40 Conduit to the garage
  • Insert a 70amp Breaker to feed the 60amp sub panel in the garage
  • Run 6/3 gauge wire from main panel in the PVC to the sub-panel in the garage
  • From the subpanel - just run the 12/2 wiring into the main circuit that is fitted up now (From the wiring that comes through the ground), Also run off the 50amp breaker from SP, the 6/3 wirirng to the Nema 14-50 outlet to plug in the EV.

The other option could be to avoid the subpanel and just run wiring to a an outlet.

  • Run a 50amp breaker & 6/3 wire + new 12/2 wiring through the garage
  • Connect the 6/3 to a 14-50 outlet and the 12/2 to the existing 110v setup.

Any tips, corrections or redirection would be appreciated.

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  • cables contain multiple wires wrapped in a sheath. If you run conduit, you can run cable but only if you like to suffer. You are also allowed to run individual wires. Now, a very important question: the "Romex" you dug up: are there any markings on it? Is it NM, UF, what kind of cable exactly and what size? – Harper Apr 4 at 1:28
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  • Thanks - Not sure if it is NM or UF. Also - what do you mean by suffer? You recommend I run the cables individually? or in the sheath? – Andy Apr 4 at 2:06
  • @andy you can't strip the sheath off and run individual wires, unless the individual wires have their own markings/ratings, which is rare. However you can buy individual wires with markings and most is dual-rated dry/wet. In cable, NM is not wet rated, must use UF. Here's what I mean by "suffer". Flat cable counts for area like round cable of the max dimension. 2 wires in conduit can't exceed 31% conduit fill, so my calcs show 6/3 and 12/2 UF will be 1.34sq.in.... /.31 = 4.332si needed. 2-1/2" is 3.976si, so 3" required. That's the trouble with cable... – Harper Apr 4 at 2:23
  • Thank you @Harper. That makes more sense now. Is this why I have seen some youtube videos of people running 2-2-2-2 wires for 240v? Or would you recommend just running 6/3 wire in 1" PVC to a SP and then run out from there? – Andy Apr 4 at 2:32
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First, using any sort of NM cable outside is right out of the question. Cannot do it; it's not wet-rated. If you want to direct-bury cable, use UF or other types; however you want to run in conduit. Running cable in conduit isn't even crazy, for reasons let's leave to another Q/A. So let's armwave that you will be using individual wires. Fortunately those are almost all dual-rated dry/wet (THHN/THWN-2, the W being Wet).

Conduit

For this reason, it's important that the conduit is either a) continuous from the panel to the destination; or b) stops at a large junction box to make a splice from THWN-2 to cable.

When laying conduit, keep your bends to an absolute minimum between access points; use conduit bodies at corners to give easy access. You see a conduit body in your picture, but you can't use that one because service wires are in it.

If you are willing to trade "being able to trench with a garden trowel" for "murderous price per foot", consider Rigid or IMC conduit, which only needs 6" of cover over top of it (12" cover for vehicle pathways). But figure like $4/foot for the stuff, and a trip or two to the hardware store to have pipe threaded. Upside: it's a viable ground path, so one less wire.

For PVC conduit, you need ot use Schedule 80 and you must have 18" of cover over top of it, so trench to 20".

Wires

I'm going to list the wires by price per 100ft, since your distance is about that. I'm getting these prices from wiresandcablesyourway.com. All or THWN-2 or XHHW.

 1 x #8 bare copper ground $37
 3 x #6 copper conductor   $57 x 3, 60A max  OR...
 3 x #4 aluminum conductor $26 x 3, 60A max  OR...
 3 x #2 aluminum conductor $35 x 3, 80A max  OR...
 3 x #1 aluminum conductor $52 x 3, 100A max.  
 2 x #10 copper conductor, $30 x 2, 20A

Aside from aluminum being less than half the price, one reason to use it is that puts your wire size larger than #6. On #6 or smaller wires, you must use an actually-white wire for neutral, which can make buying wires more expensive. #4 and up, you can mark it with tape. Grab a 5-pack of red/white/green/blue/yellow electrical tape for $4.

The 20A/120V circuit is a real problem. Because of the distance, you need to upsize the wires to #10 or you'll have alarming voltage drop. Now let's do the math on this. The two conductors are $60. You won't need it if you get a subpanel. A perfectly respectable 16 space subpanel can be had for $70. That's a no-brainer if you ask me.

  • With #6 feeder, you can comfortably use 1" conduit.
  • With #4 feeder you can only use 1" conduit if you omit the 20A circit, and it'll be a hard pull.
  • With #1 feeder you can only use 1-1/4" conduit if you omit the 20A circuit, and it'll be a hard pull.

The ground wire, presumably #8 copper, can be shared between the feeder and the 20A circuit.

The subpanel

Here we are huge proponents of huge subpanels. When buying the panel, the cost of extra spaces is super cheap. After you've fit it, and regret getting too small a panel, it's super hard and expensive. Better to skip a pizza and get a bigger panel: 16 space, even 24 space. You'll thank us later.

"Circuits" are not "spaces". A panel that claims "16 circuits" means an 8-space panel using duplex/"double-stuff" breakers. That's deceptive advertising because most circuits these days needs AFCI/GFCI breakers, and those are not available in double-stuff.

Other stuff e.g. Your diagram

The weird cable with male ends on both ends is probably a "suicide cord" for running a generator. Or should I say a "murder cord" because his plan was to plug one end into a generator and the other end into the garage feed, to backfeed the garage then backfeed the house. And maybe he turns off his main breaker first and doesn't kill a lineman. (Because when a 120V generator backfeeds a 120/240-9600V poletop transformer, the voltage on the backside of the transformer is, guess what! 9600 volts. That's how transformers work.)

Even worse, it sounds like rather than running a 120/240V /3 cable, he was using two separate cables to backfeed each leg separately. What a hokey-dokey rig. This is what fools like that do. Just remove the plug ends at one end so nobody can plug it in.

On the remaining buried cables, you might dig 'em up for a closer look. If they are NM, tear 'em out - they are ruined. NM is not wet-rated. If they are UF, see how deep they're buried. If it's <24" it's too shallow, tear it out. Otherwise you can disconnect it, pull it through the building, slip a Sched. 80 PVC conduit over it and rebury it (at the bottom, an elbow of course), and then provide physical protection up to a proper Code building entrance. And then put them back in service. Free wire :)

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