DGLEAF19
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Leaf Number: 321810

Installing 4-prong charger on 3-wire 240V distribution

Wed Aug 19, 2020 10:49 am

Hello,
I bought a '19 S-Plus a few months ago, and recently realized that I could easily tap off of the 240V circuit in my laundry room and put a 240V outlet into the garage, which is adjacent. The way we drive it, charging on 120V is fine almost all of the time (especially under Covid), so it's really not worth it for me to hire an electrician, but I figured it was such an easy thing to do, I might as well spend the $50 or so for materials and do it myself. If we limit charging to 3.6 kW and make sure we're not using the dryer at the same time, the 30-amp circuit is more than adequate.

So last weekend I went to the hardware store, bought the materials, and put in the outlet with about two hours of effort. Pleased with myself, I excitedly plugged in the car, and ... nothing happened. No charging, no blinks from the charging lights or anything. After thinking about it overnight, I realized the problem probably had to do with the Nissan-supplied charger being smart enough to recognize that I had not grounded the equipment ground socket of the 4-prong outlet. My house is somewhat older, so the circuit I'm working with has two hot conductors and a ground wire, but no neutral. So when I installed the outlet, I used the ground wire as the neutral, thinking that a 240V load should have essentially zero neutral current. Of course doing that left nothing to connect the ground socket of the outlet to, which is why the charger refused to work. Duh. So next day, I ran a jumper between the ground and neutral sockets of the outlet, plugged it in, and esto-presto the car began charging at 240V.

Here, finally, is my question: I know that this is a code violation, but on the other hand, this is precisely the way that my dryer has been running, at almost twice the amperage and on the same circuit, for over 20 years without a problem--and there is no code violation in the way the dryer is wired (it uses a 3-prong plug/outlet). Am I making a mistake here or creating an actual hazard? Should I de-energize the outlet and go back to 120V?

LeftieBiker
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Re: Installing 4-prong charger on 3-wire 240V distribution

Wed Aug 19, 2020 11:24 am

EVSEs do not use Neutral, so the correct way to connect one is with two Hots and a ground. I suggest you replace the 4 prong outlet with the correct 3 prong if there is no real Neutral available. At worst, label the outlet as having no neutral and disconnect the improvised Neutral. Two Hot and one Ground are all you need there.
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DGLEAF19
Posts: 3
Joined: Wed Aug 19, 2020 10:08 am
Delivery Date: 19 Aug 2020
Leaf Number: 321810

Re: Installing 4-prong charger on 3-wire 240V distribution

Wed Aug 19, 2020 12:02 pm

Thanks Leftie! The thing is that the Nissan charger uses a 4-prong plug, so I have to use a matching outlet.

jjeff
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Re: Installing 4-prong charger on 3-wire 240V distribution

Wed Aug 19, 2020 4:15 pm

In your case I personally would have hooked your neutral wire to the ground socket on your 14-50 outlet and leave the neutral unused on the 14-50 outlet. Where does the neutral come from, is it a dedicated wire running back to your panel or does it simply come from the box ground? Others(Whitney?) probably know the true code but I just don't like the idea of bonding the ground and neutral at the outlet. As Leftie said L2 EVSEs don't use the neutral and I don't believe the OEM EVSE looks for a neutral but it for sure needs a ground.
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LeftieBiker
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Re: Installing 4-prong charger on 3-wire 240V distribution

Wed Aug 19, 2020 7:52 pm

DGLEAF19 wrote:
Wed Aug 19, 2020 12:02 pm
Thanks Leftie! The thing is that the Nissan charger uses a 4-prong plug, so I have to use a matching outlet.
The just label the outlet "NO NEUTRAL WIRE".
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DGLEAF19
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Joined: Wed Aug 19, 2020 10:08 am
Delivery Date: 19 Aug 2020
Leaf Number: 321810

Re: Installing 4-prong charger on 3-wire 240V distribution

Thu Aug 20, 2020 3:37 pm

Thanks to LeftieBiker and JJeff. I connected the ground wire to the ground plug and disconnected it from the neutral. Charger is working like a dream.

LeftieBiker
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Re: Installing 4-prong charger on 3-wire 240V distribution

Thu Aug 20, 2020 5:27 pm

DGLEAF19 wrote:
Thu Aug 20, 2020 3:37 pm
Thanks to LeftieBiker and JJeff. I connected the ground wire to the ground plug and disconnected it from the neutral. Charger is working like a dream.
Good news! Now don't forget to label the outlet "NO NEUTRAL".
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LeftieBiker
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Re: Installing 4-prong charger on 3-wire 240V distribution

Thu Aug 20, 2020 6:10 pm

If we limit charging to 3.6 kW and make sure we're not using the dryer at the same time, the 30-amp circuit is more than adequate.
I had a thought while I was away from the site: I'm wondering how you are doing this with the Nissan supplied dual voltage charging cable, which is NOT adjustable...
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wwhitney
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Re: Installing 4-prong charger on 3-wire 240V distribution

Thu Aug 20, 2020 8:37 pm

A couple comments:

A valid allowed-only-for-existing 3-wire circuit for a dryer or stove outlet actually is an ungrounded 240/120V circuit, it has a neutral but no EGC. The dryer or stove is allowed to use the neutral for bonding the case of the equipment, something not otherwise allowed downstream of the electrical service disconnect.

I think the proper way to do this install is to use a NEMA 10-30 receptacle (again, ungrounded 240/120V), and then to procure a small pigtail that is 10-30P to 14-30R in which the 14-30R ground is connected to the 10-30P neutral. That way the fixed parts (the 10-30R) are all wired in the standard way, and all the "weirdness" is in the pigtail, which can be appropriately labeled.

Cheers, Wayne

alozzy
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Re: Installing 4-prong charger on 3-wire 240V distribution

Thu Aug 20, 2020 9:23 pm

FWIW, a 10-30p to 14-30r adapter cable can be purchased here:

https://bit.ly/34jGfwb
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