wiring a convenience outlet with an EVSE (car-charging station)

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RustyShackleford

Minister of Fire
Jan 6, 2009
1,341
NC
As mentioned in some other threads, I'm moving an EVSE, that was on the side of the house, out to the parking area. I'm using rigid conduit, cheaply acquired at the scrap-metal yard, so it only needs to be buried 6" deep (it never crosses the parking area) and I needn't fear hitting the numerous other utilities out there.

For the EVSE, I'm running three strands of 8awg THWN (it's a 40amp unit meant to be on a 50amp breaker), ground and two hots. Yes, I know the ground could be 10awg, but the local electrical place didn't sell 10awg by the foot, so it was actually cheaper to use 8awg (rather than buy a roll of 10awg). The round-trip distance will be about 50ft, so I expect an acceptable voltage drop of about 1%.

Since I'm running conduit, why not put a 120v convenience outlet beside the EVSE ? I could just include two strands of 12awg (the EVSE 8awg ground can serve for both circuits). But what about just running a 12awg neutral and using one of the EVSE 8awg hots for the hot side of the 120v outlet ? Is that ok ? I suppose it's possible that if I were putting greater than 10amp load on the convenience outlet while charging the car, the 50amp breaker could trip; or if I put any load on it continuously while charging the car. But the wiring will always be protected. Or if I'm not charging the car, but the 120v load has a failure and it drawing way more than 15 or 20 amps (but less than 50), it would never trip the breaker; but it's out on the driveway, so not a big safety concern there.

Probably silly to worry about any of these issues just to save 40ft of 12awg wire. Main thing is the 3/4" RMC will be pretty crowded.
 
You ought to protect the receptacle at whatever its rating is (15A or 20A). Not that *you* would ever do it, but when "someone" decides to plug in 40A worth of xmas lights into that outlet, it will melt and a fire could easily ensue. OK, it's out in the driveway so it probably won't set your house on fire, but could still damage your property or hurt someone.

You can put in a mini load center with as few as two spaces fed by the EVSE circuit. Pop a 15A breaker in there, and feed the receptacle off of that. Or, pull a dedicated circuit in the conduit as you suggested.

Oh yeah, and you will need a neutral. For a branch circuit, the neutral needs to be sized the same as the hots so 8AWG if you go the load center route, or 12AWG if you pull a dedicated circuit for the convenience receptacle.
 
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You ought to protect the receptacle at whatever its rating is (15A or 20A) ...

You can put in a mini load center with as few as two spaces ...
All correct. I'm being dopey for even considering what I proposed. Worked too hard trenching for the conduit :)
 
40 A of christmas lights... - you'd be able to see that from the moon in this LED time...

(And I don't see him plugging 6 block heaters in at once in NC either :p )
 
you could just run some wire for the plug from one of your existing outlets on the house (as long as that circuit is not to capacity) Would be cheaper than installing a load center to run off the 50 amp breaker..

What you were proposing to do is against every building code out their... Not to mention if something ever happened to that your insurance would null and void your insurance if that was the cause..
 
you could just run some wire for the plug from one of your existing outlets on the house (as long as that circuit is not to capacity) Would be cheaper than installing a load center to run off the 50 amp breaker..
Pulled the wire yesterday. Green/black/red 8awg, plus black & red 12awg. Feeding the 12awg off an existing circuit in the house, as you suggest. Sharing the ground between both circuits, which is fine. Realize the ground could be 10awg, but I didn't have any. Need to re-identify one of the 12awg wires as a neutral.
 
I think you may have an Issue with the 120V circuit. Being outside it should be on a GFI breaker. The neutral for that goes to the GFI breaker.
If not what you did will work.
 
I think you may have an Issue with the 120V circuit. Being outside it should be on a GFI breaker. The neutral for that goes to the GFI breaker.
If not what you did will work.
Or just use a GFCI receptacle device
 
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