Wiring a 3 wire 220v dryer receptacle with a 4 wire setup

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BigEdgar

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I have 220v service to a box in my garage. It's served by a 4 wire setup (two hots, a neutral and a ground). I want to be able to charge my electric vehicle from this location. The EVSE (ev charging cord) that I'm going to use comes with a 10-30p plug, which requires a 10-30r receptacle. This receptacle only takes 3 wires.

Forget about all of the EV stuff for a second - essentially I need to install a 10-30r dryer receptacle in a location that's served by 4 wires. In my research on how to wire this up, I understood that the right thing to do in this situation is to wire the two hots and the ground, and leave the neutral wire capped in the box. However, the instructions for the receptacle state that I should use the white wire (neutral) and the two hots. Which is correct?
 

Reach4

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That is odd. Would you care to identify the charger?

Does the neutral pin of the plug either show voltage or continuity to the chassis of the car?
 

BigEdgar

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Here's a picture of the charger:
81AnkCUyXOL._SL1500_.jpg


Here's a link to the actual product: https://www.amazon.com/Portable-Ele...id=1492269193&sr=8-2&keywords=duosida+charger

Here's a photo of the receptacle installation instructions:
PsTj7Xv.jpg


And here's a link to the actual receptacle that I'm installing:
https://www.lowes.com/pd/Utilitech-30-Amp-Dryer-Power-Outlet/3775475
 

BigEdgar

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The adapter is not a bad idea - I'll look into that.

FWIW, other 220v EVSEs that I've installed (Clipper Creek and Schneider) only use the two hots and the ground - so you end up just capping the neutral in the box (as long as the neutral is connected to earth ground back at the panel).
 

Jadnashua

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An EVSE does NOT use a neutral wire (well, not a 240vac one anyways!)...it uses two hot leads and ground. In case you really wanted to use that receptacle some time for a dryer, I'd wire it up using all four wires, then either buy or make an adapter to then plug in your EVSE to it. The EVSE has a built-in GFCI equivalent circuit, so you don't need that on your panel supplying the receptacle. Should you eventually want to pick up an EVSE or EV that could use more current, you may want to run at least 8g (for a 40A circuit), or 6g, if you think you might want to go to a 40A EVSE (50A circuit). The 80% rule applies when powering an EVSE, so make sure your bits are all of sufficient capacity.
 

Stuff

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The charger's specs show that is is a 16 amp charger. They sell one that looks like they cut off the end and replaced with a with a 6-20P. That would be a lot easier to deal with as there is no neutral.
 
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BigEdgar

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Thanks for all the thoughts, feedback and ideas, everyone. I really appreciate the expertise and opinions in these TerryLove forums - always good stuff!

Jadnashua - thanks for the clarification on EVSEs and their lack of a neutral. That helps explain a bunch.

Stuff - I considered going with a 6-20p instead, but the breaker is 30 amp and my understanding (which may not be correct) is that the breaker at the panel and the receptacle should match amperage. I don't want to drop the breakers down to 20 amps as this setup may not be that permanent (we may eventually want to install a dryer at this location and move the EV charging to a different location). If I could have a 6-20 receptacle on a 30 amp breaker, that would solve my issue.

So my choices appear to be:

1. Change the 30 amp breaker to 20 amps at the panel and go with the 6-20 setup (receptacle and plug)

2. Keep the 30 amp breaker and wire up a 14-30r. Then buy/build a 14-30 --> 10-30 adapter. I haven't been able to source one of these (the product that Stuff referred to earlier in the thread is no longer available).

3. From my research, it appears that most EVSE manufacturers discourage the use of the 10-30 setup as it relies on a neutral instead of a ground, and that neutral always has the potential to carry current back to the EVSE (and thus the vehicle). Seems like most of the EVSE providers that have 10-30 plugs are banking on the fact that the neutral is grounded to earth back at the panel. So my third option is to hook up the 10-30r and bank on the neutral serving as a ground. Not ideal.

None of these options is ideal. Maybe I should just throw away the car and go back to gas :)
 

Jadnashua

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There's nothing that says you have to put a smaller CB on that circuit...just like when you plug in your phone charger into the wall, it's still (likely) a 15A circuit - you don't change it to a 1A breaker. The CB protects the WIRING, not the device. If the device is hard-wired, and dedicated, the device's installation instructions may dictate a specific protection device, but that normally does not happen when it is a plug-in device. Now, a device at the end may have some internal protection, but it is not dependent on the receptacle it is plugged into to provide it (this differs some in other countries).

There's no place to wire neutral into a typical 240vac EVSE...it only has three wires in its pigtail or plug, even if the plug might have 4 pins. IT has L1, L2, and ground. You do not want to try to substitute neutral for the ground connection in the plug of your device. There's nothing that says you can't cap the neutral feed, should you want to.

Neutral is a CURRENT carrying wire...ground should never have current on it unless there's a fault. Even though neutral is bonded to ground at the power panel, it is functionally different than the ground, safety wire...neutral must be insulated, and the same size conductor as the L1 and L2 leads, ground can typically be smaller...it only exists to trip the circuit breaker or fuse, and thus, won't overheat from constant use when it is smaller gauge since it should have no current on it at all. There's a reason why all new appliances keep neutral and ground separated while older ones did not...it's safer. It can still work when connected, but it isn't as safe as having them separate at the point of use.
 

BigEdgar

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Thanks Jadnashua. Section 210.21 of the NEC says that a 30 amp circuit may only have a 30 amp receptacle. So unless I'm mis-interpreting that section of the code, I think I'm stuck with either changing out the breaker or figuring something else out. It would really be nice if the EVSE manufacturers would come up with a 14-xx plug. I could probably rig something up myself, but I'm not excited about having the neutral from the 14-30 plug hanging around with nothing to tie onto...
 

Jadnashua

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While I may be wrong...I think you'll find that the intent of the code is to say that you can't have a higher capacity plug on a supply line than the wire allows. AN example of this is that you could put a 15A receptacle on a 20A circuit, but you can't put a 20A receptacle on a 15A circuit. They do make an exception for stoves and dryers, for some reason. There isn't a 40A receptacle, so you can use a 50A one on a 40A circuit.

Other than the extra cost to have a 4-wire cable and only using 3 leads...there's nothing wrong with it if you cap each end. But, do not arbitrarily tie ground and neutral together except at locations specifically allowed.
 

BigEdgar

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Yeah, it's a little odd. Code allows an exception for 15 amp receptacles on 20 amp breakers, and also on devices like dryers and stoves, as you mentioned. But other amperage circuits are supposed to be matched by like rated receptacles.
 

Jadnashua

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All of the EVSE's that I have looked at do not need or want a neutral...yours might, and have some 120vac circuits in it (the only thing I can think of is that they use a 120vac input to the internal power supply that controls the logic where (nearly) everyone else uses either a universal or 240vac supply). Because the EVSE has an internal GFCI like circuit, it should still be safe without a ground. When all else fails, follow the instructions.

FWIW, essentially, the EVSE is just a fancy power switch. It does have some safety interlock logic, so does need a power supply to run those circuits, but other than that, it's pretty simple. It has a couple of low-level outputs: a pilot signal that is interpreted by the vehicle to tell it how much power is available from the device (the vehicle then adjusts itself so it doesn't overload the device), and a couple of interlocks that run through the car and back to determine when the latch is closed and the car is ready for power to be applied, which usually is done with a power contactor (heavy duty relay), but may be solid state on lower powered devices. Most of them make a clunk when activated, which is because of the contactor being energized.
 
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