I wanted electric run to my barn after I had it built. My cousin is an electrician, and I asked him the best way to do it. The first thing he said was, “Don’t get a ‘demand meter’ for the barn. While the installation will be ‘free,’ the power company will charge you a lot for each kilowatt-hour.” I also didn’t want to power the barn from a circuit breaker in the house, as it would require a hole to be drilled in my basement foundation. So I installed dual 250 MCM load lugs inside my meter box, rented a trencher, and then ran 250 MCM UF aluminum wiring to my barn. I then installed a 100 A main breaker panel in the barn. Not sure if what I did is “code,” but it has been working well for the past 12 years.
I suggest get a professional to do it. And first check with your homeowner’s insurance company. They aren’t thrilled about home charging stations. You may be okay with a detached garage, but they might not cover the garage anymore or charge you significantly more than before.
QFT
When I installed our Tesla wall charger I did it by the book (60A / 4 AGW) rather than the “good enough 50A / 6 AGW” way you’ll see on Youtube. What’s another few hundred dollars after buying a $50K car to ensure that my garage doesn’t burn down.
I bought a high quality NEMA 14-50 socket from an electrical supply store to replace the $10 Home Depot version, from the recommendation I found in a Tesla discussion group on this topic. IIRC it cost in the neighbourhood of $160. It’s designed for industrial applications.
How does the charger know what the whole house is drawing?
The flaw I see in house management systems is the feedback to the service. One can imagine systems where, for example, the menagement system lowers peak load by preemptively cooling the freezer before cooking or laundry happen, or varying the hot water tank by a few degrees, so a lot of loads aren’t running at once. (As well as minor management of the temperature). Unfortunately moern appliances are not yet that smart (for example, a fridge or freezer with a temperature sensor the master controller can read and ability to receive “run now” commands) and gven the lifetime of most appliances, it will be a long time before the house is that smart.
Current transformers clamped around the service-entrance conductors.
In my detached garage both the welder and the wall mount electric heater use the same 240V outlet. It is impossible for both to operate at the same time because you need to unplug one to plug in the other.
Sounds like in this situation the charger and whatever appliance would be on the same line but different outlets. You plug in the the charger, the wife, or whomever, starts the dryer either not knowing or forgetting about the charger and “pop” you trip the circuit. Too much to go wrong here.
As suggested, talk to a licensed electrician.
There is nothing not “by the book” about feeding a Tesla wall connector with 50A (8 AWG copper wires in conduit, THHN etc) or 55A (6 AWG copper NM) - as long as you use a 50A breaker and tell the box that it’s on a 50A circuit at set up time. That’s 100% code-compliant and safe.
If you were to use <60A wire while telling the box that it’s on a 60A circuit, that would not be “good enough”, it would be a clear code violation.
48A draw and using the 80% rule is “by the book”.
You seem to be trying to imply that 48A is preferred (according to code, etc) over any of the other options that the Wall Connector supports. This is not the case - all six circuit size options listed in the instructions at https://digitalassets.tesla.com/tesla-contents/image/upload/gen-3-wall-connector-installation-manual.pdf are equally “by the book”. None is better than another as far as code compliance and safety are concerned.
All right, a couple new pieces of info and some clarification.
My house is Natural gas for Furnace, stove, water heater and dryer, so no worries about this conflicting with a massive load from other devices.
The garage actually has 2 circuits (one was very very lightly labeled), a 15a and a 20a.
Our house is 110 years old and 100amp service is plenty. It’s 1700sft and uses gas appliances and heat, so it doesn’t need 200 or 400 amp service.
The garage is about 10 feet from a pole so I will check into the possibility of having a new ev-only line run directly there.
I don’t think I’m allowed to open up the meter and run new lugs or whatever…but if I am I would be interested to hear more about how that’s done.
Lastly… I do a lot of DIY, but outside of putting in new switches or replacing light fixtures, I don’t (bleep) with electrical. A licensed and insured professional (in electricity) will do this work.
We have it set up for the max. And I’ll point out that the people on Youtube I referred to fully expect to charge at 48A on a 50A circuit with no problems because 50 > 48. Also I double-checked with a journeyman electrician and he agreed that pulling 48A on a 50A and 6 AWG circuit is asking for trouble because “home electicity isn’t that clean”.
If there aren’t many loads in the garage (just lights and the door openers), there’s a decent chance you could put all the 120V loads on one of those circuits and switch the other circuit to 240V and dedicate it to the EVSE. Even 12A/240v charging should be plenty for you driving a Polestar 2 7000 miles a year.
Putting a 48A EVSE on a 50A circuit is just plain illegal, as it’s a continuous load in excess of 80% of the circuit size. It has nothing to do with the “cleanliness” of “home electricity” though.
If you’re stuck with a 50A circuit for some reason, provisioning a “48A capable” EVSE to tell it that it’s on a 50A circuit (so that it tells the EV the draw limit is 40A) it fully legal and “by the book”.
Well yes of course. Again, I am referring very specifically to people trying to pull the full 48A off of a 50A breaker.
Yes, there is once circuit labeled “Garage Freezer only” and it’s 20amp. I don’t want to know what size freezer they had in there, I just need to find that specific outlet, which I hope would be marked somehow but that’s a lot to hope for.
The only loads besides lights/doors would be any tools I use, like my 12-inch miter saw, circular saw, drill, etc. Nothing particularly heavy duty, and if I’m using tools in there I am not opening the doors or charging the car while doing it.
IF this wiring in the garage is relatively new and up to code, the freezer circuit should be the one that is not on a GFCI and it should be a sole outlet… Hopefully it’s 10/2 Romex which I believe should be ok for 15 amps/220v for your car. I’m not sure if the Polestar comes with a charger–our Caddy came with one where you couldn’t set the load. Just got a hardwired Chargepoint where you can set the amperage.
Yes, that’s almost certainly a perfect candidate for swapping over to 240V, as long as it can be confirmed that it was truly dedicated.
It may be a faceplate that has only one single socket (not a duplex receptacle), in which case it should be a 20A receptacle (one slot shaped like a sideways “T”). If it’s a duplex receptacle it could be 20A or 15A, in which case it might be impossible to distinguish from the ones on the 15A circuit visually. You’ll just have to turn that breaker off and see which receptacles go dead.
It should be less than $100 in parts besides the EVSE itself ($20-$40 for a two-pole breaker depending on brand, plus maybe some fittings, wire, and conduit if you want the EVSE mounted somewhere other than right on top of where the old freezer receptacle was). Hopefully well under $1000 in labor but local markets vary.
There’s a good chance you can get a 30% US federal income tax credit on the price of the whole job (EVSE purchase plus electrical bill) and many states have similar tax credits as well, so that may reduce the effective cost to you significantly.
It’s also worth checking with your electric utility if they offer a discounted “EV charging” rate in exchange for letting them limit your charging to a specific time range. Savings can be quite substantial but they usually have a fairly short list of supported EVSEs in order to participate.
10 AWG copper wire is good for at least 30A. Voltage drop can be an issue on very long runs, but for 240V at 24A (the 80% continuous limit for a 30A circuit) it only hits 3% (a decent general limit) at a length of 150 feet. 10 AWG would be the size for 20A is the wire is aluminum, but that is exceedingly unlikely for a garage added in the 90s - small-gauge aluminum was well out of vogue by then.
A 20A circuit is likely to be 12 AWG copper (unless the run is very long).
And it shouldn’t be Romex, since it should be in conduit. How do you accurately tell the gauge of individual wires? Calipers? Is direct bury still to code?
Direct burial is still legal. The buried part shouldn’t be NM (“Romex”) but if it was DIY’d, you never know. If it’s buried, the most likely cable type is UF (or newer UF-B) for a short, small-circuit run. UF resembles NM, except it’s usually gray and each internal wire is totally encased by the outer insulation individually and there is no paper (vs. NM which has all the conductors together, then paper, then the outer cover).
Either way, the underground wire type might not appear in the receptacle box. There may be a splice from the underground type to an indoor type at a junction box near where it enters the building.