3 cars with stock evses on 20 amp curcuits?

edit: the part below the --- is the original post, jump to page 4 at least if you want the current scoop.

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My current charging situation is me and a coworker sharing two EV only parking spaces with 4 x 120v jacks on the curb. Turns out both pairs of outlets are on the same breaker. Word on the grapevine is that the breaker is 20 amp but I haven't personally seen it.

My coworker plugs in at 6am and the first time I plugged in between 2 and 2:30pm. The other car unplugged at 2:35pm. The breaker tripped at 4:09pm.

I was surprised that the breaker tripped while only one car was charging but apparently the heat of the cable run hadn't dissipated and the additional heat of the afternoon sun was enough to trip it.

Since then we have been charging one car at a time but if I get an evseupgrade or openevse I might try to charge at the same time by lowering my amperage.

So given the overlap worked for 15 minutes and the load was definitely 24 amps how far do I have to turn down the adjustable EVSE #2 if EVSE #1 is fixed at 12 amps?

Down to 8 amps and push the 20 amp limit as the overlap is only a couple of hours a day?

Down to 6 amps to give more headroom during the overlap?

Either way I'd start a new session at 12 amps after he leaves.

And hopefully we'll get a new circuit down the road but for now until management decides how much they want to spend I have this situation.

Ingineer (Phil) and the others here who know this stuff will no doubt comment.

I plugged into a 120 volt circuit in a four-gang box that had two other cars plugged in. At the time my EVSE Upgrade was pulling 8 amps. After the other cars left it was pulling 12 amps. I don't know how that works. Maybe they were down to just a trickle charge.

Paul

The best and safest practice is to never draw the maximum current from a socket continuously. They are rated assuming that they won't be loaded that way. Continuous loads- defined as one hour or longer- shouldn't be more than 80% of the maximum. So if your coworker is plugged in drawing 12A on 20A circuit, and you want to plug in too, for an hour or more, you should draw only 4A. I'd recommend using a timer to just have your car come on with the 16A draw that the EVSEupgrade will allow 15 minutes after your coworker leaves, if they can be counted on to have left by a certain time.

It seems to me that this is an example of a common situation: multiple EVSEs and a limited total amperage amount to service them all (together with the possible complication of there being multiple circuits). An example is having a house with 2 EVSE circuits for up to 2 EVs, but needing to limit the total EV current draw to 30a. I am going to assume that solutions are being worked on that safely distribute power and yet try to maximize the total output to each EVSE in a dynamic, flexible manner. There is already mention of this in the 2014 NEC Article 625.41 (Rating): "automatic load management system". However, I didn't find any existing products when I did a Google search for this post. It appears to be a complex problem that probably requires communication w/ the EVSEs, among other things.

nedfunnell said:

So if your coworker is plugged in drawing 12A on 20A circuit, and you want to plug in too, for an hour or more, you should draw only 4A. I'd recommend using a timer to just have your car come on with the 16A draw that the EVSEupgrade will allow 15 minutes after your coworker leaves, if they can be counted on to have left by a certain time.

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The least the evseupgrade will do is 6a, can't do 4a and the other car won't have the adjustable amps, it'll be stuck at 12a. So I'll take your vote as to use the 6a option.

Also although the evseupgrade might do 16a I've read that the Leaf will only accept 12a on 120v. I'm not sure what car accepts the 16a 120v that the evseupgrade can do.

Finally I'm not going to be drawing 20a from one socket, it might be 20a on one circuit but there are 4 sockets on the circuit and the other two will be empty. The proposed loads are:

12a on socket 1
8a on socket 2

or

12a on socket 1
6a on socket 2

and we know that

12a on socket 1
12a on socket 2 didn't trip the breaker during a short overlap (think 15 minutes or so)

dhanson865 said:

The least the evseupgrade will do is 6a, can't do 4a and the other car won't have the adjustable amps, it'll be stuck at 12a. So I'll take your vote as to use the 6a option.

Also although the evseupgrade might do 16a I've read that the Leaf will only accept 12a on 120v. I'm not sure what car accepts the 16a 120v that the evseupgrade can do.

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2013+ LEAFs with the 6.6kW charger can apparently do up to 27.5A @ 120V to match the 27.5A @ 240V. Only 2011-2012 (and maybe 2013+ without the QC option?) are stuck at 12A @ 120V.

You can't turn it down far enough, sorry. 16a total is all you should draw on a 20a circuit, and that's assuming the wiring is sound. You'll have to work out a deal with your co-worker where you either charge one at a time, or both of you get an EVSE that can be turned down to 8a.

Do both of you guys need to charge to get home? If not, only plug in if you actually need extra range that day. Call or text to confirm the other guy doesn't need it, too.

No, 2011 and 2012 can do 16 amps at both 120 and 240... And the 2013+ is 6.0Kw output by the way... Nissan changed the rating from charger output power to input power on the 2013+... Why? Perhaps to make it look somewhat more impressive...

ishiyakazuo said:

2013+ LEAFs with the 6.6kW charger can apparently do up to 27.5A @ 120V to match the 27.5A @ 240V. Only 2011-2012 (and maybe 2013+ without the QC option?) are stuck at 12A @ 120V.

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dhanson865 said:

...
and we know that

12a on socket 1
12a on socket 2 didn't trip the breaker during a short overlap (think 15 minutes or so)

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No, you do not know that.

The first vehicle had been charging for a long time.
Very likely was not drawing anywhere near 12 amps.
If you loaded a 20 amp circuit breaker with 24 amps it would trip very quickly unless defective.

It is a little surprising the breaker tripped that long after the first vehicle was unplugged.
But it has nothing to do with the temperature of the wires.
The circuit breaker tripping has to do with the temperature of the breaker trip device.
When both vehicles were charging you must have gotten the trip device close to tripping.
It then took a while for the single vehicle 12 amps to finally make it trip.

But as others said, it is irresponsible and dangerous to operate a 20 amp circuit above 16 amps for an extended period.

The operation of the breaker is suspect though, and it probably should be replaced.

Nissan only recommends the 120V EVSE for emergency / convenience use for very good reasons.
People overloading circuits and increasing fire hazard is one of them.
Just don't do it.

Most employers aren't real pleased when employees cause a fire :shock:

ishiyakazuo said:

dhanson865 said:

The least the evseupgrade will do is 6a, can't do 4a and the other car won't have the adjustable amps, it'll be stuck at 12a. So I'll take your vote as to use the 6a option.

Also although the evseupgrade might do 16a I've read that the Leaf will only accept 12a on 120v. I'm not sure what car accepts the 16a 120v that the evseupgrade can do.

Click to expand...

2013+ LEAFs with the 6.6kW charger can apparently do up to 27.5A @ 120V to match the 27.5A @ 240V. Only 2011-2012 (and maybe 2013+ without the QC option?) are stuck at 12A @ 120V.

Click to expand...

I do not believe the 6.6KW will ever do that on 120, I believe it will only charge at 3.3KW rates.

dhanson865 said:

My coworker plugs in at 6am and the first time I plugged in between 2 and 2:30pm. The other car unplugged at 2:35pm. The breaker tripped at 4:09pm.

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I find it very suspect that an hour and a half later the breaker tripped with only your car charging. Are you sure it's a 20 amp breaker? Is the same breaker feeding some other loads perhaps, maybe a garage door opener or some utility lights that turned on at 4:08

I would verify it is indeed a 20 amp breaker and verify it is only feeding those outlets. You should be fine with 12 amps of charging with either a 15 amp or 20 amp breaker, but you could be safe and dial it back to 10 amps to be sure.

Then I would set your charge timer to start at 4:00 PM.

What kind of car does your co-worker have? I think the iMiev (I know the odds of that are rare LOL) and the volt can be set to draw only 8 amps through their stock EVSE (I think the iMiev has a switch on the evse, the volt is enabled through the cars system). If they have one of those you just have to ask them to only charge at 8amps and then you can get an evse upgrade. It may be advantageous for them to get the upgrade as well.

Talking to them is probably your best bet. They may not need the extra charge from 2-4 and might let you unplug them or they may be willing to plug you in when they leave if they need it but you don't.

BrockWI said:

dhanson865 said:

My coworker plugs in at 6am and the first time I plugged in between 2 and 2:30pm. The other car unplugged at 2:35pm. The breaker tripped at 4:09pm.

Click to expand...

I find it very suspect that an hour and a half later the breaker tripped with only your car charging. Are you sure it's a 20 amp breaker? Is the same breaker feeding some other loads perhaps, maybe a garage door opener or some utility lights that turned on at 4:08

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It's an office building with hundreds of employees and hundreds of parking spaces. There are no garage doors though it could have been a janitor or lawn care worker plugging into the same circuit.

I don't have access to the breaker or any sort of wiring schematic. The cable is running the length of the building (several hundred feet, unknown if it is in conduit underground or inside the building) then definitely in a conduit underground to the curb.

I was told verbally that it was a 20 amp breaker but for all I know its a 50 amp breaker and the guy can't read.

ahhhhhhh, that makes more sense, who knows what got plugged in then, but just one EVSE should be fine. I would still set yours to start at a safe time past when the other worker leaves, say 3pm?

What style outlet does it have? If it is the standard two vertical slots, it could very well be only a 15 amp since that is all that type of socket is rated for. If it has the horizontal tab on one of the slots then it could be either a 15 or 20, most likely... By code, it can't be more than a 20 amp breaker regardless.

dhanson865 said:

I was told verbally that it was a 20 amp breaker but for all I know its a 50 amp breaker and the guy can't read.

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minispeed said:

What kind of car does your co-worker have?

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The guy at the desk next to mine has a Leaf, he and I are currently charging one at a time. Often he unplugs at 11am for a few minutes to grab lunch and again at 1pm or 2pm when he has enough charge to let me take over and I charge from then to 6:30pm. Either way I always know what he is doing and he always knows what I'm doing.

If I can get away with 6a charging on top of his 12a I would overlap that combination from 10am to when he unplugs and then unplug mine and reset for 12a charging and charge from then to my end of day.

If I can't get away with 6a charging during the overlap I'll keep doing the one person at a time charging until they add another circuit in the parking lot.

as is we are Leaf #2 and #3 in our lot and Leaf #1 is graciously not charging at all in the lot right now since she lives closer to work than we do.

Long term all it will take is for another one or two to buy an EV or PHEV and bam we'll have more problems.

TomT said:

What style outlet does it have? If it is the standard two vertical slots, it could very well be only a 15 amp since that is all that type of socket is rated for. If it has the horizontal tab on one of the slots then it could be either a 15 or 20, most likely... By code, it can't be more than a 20 amp breaker regardless.

dhanson865 said:

I was told verbally that it was a 20 amp breaker but for all I know its a 50 amp breaker and the guy can't read.

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did you catch that it is 4 GFCI outlets in a single box on the curb? yah I'm pretty sure the GFCI outlets are 20 amp style (5-20 not 5-15). I'm not positive as to the situation being to code. Some electrician made the current setup but I have no idea what he had to work with, what his orders were, who he was, if he was competent, etcetera.

But I also know that it's a silly long run of cable.



The small square in the parking lot is the parking space, the small square nearest that inside the building is approximately where the nearest breakers are but I was in that room with a staff member and the breaker wasn't there, told the next day that the breaker was at the other end of the building.

I just made a random guess on the path of the cable underground.

No, sorry, I missed that... Still, unless each outlet has a separate feed in which case there would be multiple breakers, the breaker rating can't legally be more than the capacity of one outlet...

dhanson865 said:

did you catch that it is 4 GFCI outlets in a single box on the curb? yah I'm pretty sure the GFCI outlets are 20 amp style (5-20 not 5-15)

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TomT said:

No, sorry, I missed that... Still, unless each outlet has a separate feed in which case there would be multiple breakers, the breaker rating can't legally be more than the capacity of one outlet...

dhanson865 said:

did you catch that it is 4 GFCI outlets in a single box on the curb? yah I'm pretty sure the GFCI outlets are 20 amp style (5-20 not 5-15)

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understood but I did an edit there while you were replying and...

I'm not positive as to the situation being to code. Some electrician made the current setup but I have no idea what he had to work with, what his orders were, who he was, if he was competent, etcetera.

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It's a pig in a poke at this point (meaning I don't know its true nature or value).

dhanson865: If GFCI outlets, and a long cable run, doesn't that bring in the possibility that the trip was due to a ground fault? Do you know if the breaker is GFCI?

Perhaps some useful info about current draw could be gleaned by investing in a Kill-a-Watt that you could share with the other Leaf owner?