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Interesting. Our paperwork says the electric car charger add on was to include a dedicated circuit for 240v 50amp NEMA 6-50 outlet.
I guess maybe the outlet is for 50amps but they don't necessarily have to provide that many at the box?
Also, how do I tell if it has its own dedicated circuit?
I guess maybe the outlet is for 50amps but they don't necessarily have to provide that many at the box?
Also, how do I tell if it has its own dedicated circuit?
It should have a 50 amp breaker for a 50 amp outlet. It seems that 6-50 outlets often only have 40 amps. I found this was also the case on my brother's garage and now I limit the rate to 32 amps when charging there.
Can you tell what the wiring is labeled as? It might be possible to upgrade the breaker to 50 amps if you have the correct gauge wiring.
I do not think any of the wiring is exposed any longer and I don't think I have any photos of it close up before it was covered up. Shoot.
Same problem at my parents house. They have a 6-50 with a 40A breaker. I believe those are typically used for welders and that's just the "standard" for some stupid reason. I also no longer have exposed wiring to verify the gauge of the installed wires and the jackets are trimmed too close to see anything in the box or the panel.. I'll be dialing down for a while. Someday I'll be bringing a drywall saw to confirm the wiring jacket.
Correct. There is, however, a risk. The car *may* forget the current is dialed down. Either the GPS gets confused or something gets reset.
The breaker should protect the wire if it happens to be undersized.
It is just something you should double check occasionally.
And yes, 32A should be plenty to meet the needs of most normal folks for charging an EV.
Tam
Well-Known Member
You can still your Tesla with 40A breaker. You just have to make sure to dial down the charging ampere setting from inside your car down to 80% or your breaker.
That means your car got to say it's charging at the maximum of 32A.
However, your setup is not approved by electrical codes and if your car is plugged in a 6-50, it automatically thinks that the breaker is 50A and your car would automatically set its charging Ampere to 40 (80% of 50A is 40).
In so doing, your circuit might risk overloading and electrical fire.
Only because the default charging with that adapter is 40 amps, which is too much for the circuit. The car will charge just fine on 32 amps. Tesla is being conservative with the requirement, because (as noted up-thread) the car can sometimes "forget" that it was manually dialed down to a lower setting, and revert to the default. At 32 amps, all will be fine.
I'd recommend getting an electrician out to check on what size wire was installed. If it's #6, you can probably have him/her simply swap out the breaker for a 50 amp one, and be all set. Not expensive.
A solution to the issue with the car reverting to the default 40 amp charging current is to get a wall-mounted EVSE (aka "charger"), and set it to enforce the 32 amp limit. Tesla's HPWC will work best because it has the right connector on the cord, but there are a number of other brands that work well too. If you use one that terminates with a J1772 connector, you'll need to use the adapter.
I'm curious - has anyone experienced the geo current limit loss themselves? I charge in two locations, both with the location limiting current. And for the past 2 years, I've never seen one forgotten once. I still regularly check, just to be safe. But I'm wondering how common this phenomenon actually is.
I believe this is incorrect information. As I understand the code requirements (I'm not a pro), the limit is 80% if the load is continuous. (not a Tesla decision).
Yes, it's been reported here several times. Which means it's happened many times more than that, as most Tesla owners are not on TMC. When it has been reported to lose the setting it's usually after a firmware update, just as other settings have been lost after firmware updates.
And it doesn't have to happen often to cause a fire. It only has to happen once.
Yes, NEC article 625 (specifically 625.14) specifies that electric car charging is always classified as a continuous load (regardless of actual charge time).
You're still protected by the 40a breaker if the wiring is sized to 40a and not 50a.
An electrician could guess at the gauge and replace the breaker if no label on the jacket is visible. They may guess wrong, in which case staying with the 40a breaker is safer.
To know with 100% confidence, might have to cut a hole in the wall. One could use a single outlet blank plate to cover to avoid drywall repair.
I *almost* wish that Tesla made the 6-50 adapter with 32a built in limit.
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A workaround (which could help @ChrisH as well) - order the Canadian 14-50 adapter, which automatically sets the charge rate to 32A, then buy or build a 14-50R to 6-50P adapter.
Outlet adapter - NEMA 14-50R to 6-50P Adapter
UMC adapter - Tesla — NEMA 14-50 - be sure to select Canada from the drop down, and (just to be safe) add a note to the order saying you intended to order the Canadian version, not the US.
Although, if you want to get pedantic, this setup would probably be a code violation, since Tesla says not to use extension cords, and the NEC requires you to follow the manufacturers requirements.
No matter how pedantic, it would still be safer because the current limit would be enforced by hardware and not subject to the software limit that can be lost in a firmware update.
One other comment - the @ChrisH install is almost certainly #8 wire because #10 is definitely too small for a 40A circuit. #8 would be OK if it was 75C rated wire in conduit, but it's not, it's NM-B. That's the only reason that it can't be upgraded to a 50A breaker.
The other alternatives would be to install a Wall Connector, set for a 40A breaker (hardwired or wired with a 6-50 plug) or a 32A J1772 EVSE that comes with a 6-50 plug already installed. This Clipper Creek unit is just one example, but it would require using the Tesla J1772 adapter all the time. My suggestion - just get the Tesla Wall Connector and leave the Mobile Connector in the car.
Clumsy wording on my part. Tesla is required to go by code ("being conservative" wasn't the right phrase), and I've been told that code doesn't allow you to get by with a programmed limit in the device (car in this case). Somebody could plug something else in without the reduced setting and cause an issue.
I think the core issue is that the 6-50 outlet is really designed for applications that aren't continuous draw, where the lower breaker value and wire size is fine. Not to point fingers, but the standard for charging applications is a 14-50 with a 50 amp breaker. What was your electrician thinking?
Bottom line, the post by miimura is probably the best:
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