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Tesla wall connector question.
- Thread starter Darthbenji
- Start date
You set the switch inside it to match what the actual circuit is that it's installed on. The owner's manual that comes with it shows you what that switch should be set to. That is a set it once and forget it thing that you never need to touch again. That sets the total capacity available.
Then, the car will draw whatever it needs to.
Then, the car will draw whatever it needs to.
The HPWC is basically just a smart switch. It passes line power on to the car, along with a signal telling the car how much it is permitted to pull (the signal for how much the car is allowed to pull is set by a rotary switch inside the HPWC, which the installer should have set to match the wiring it's connected to.) The HPWC isn't consuming or transforming any of the power (beyond a trivial amount for its processor and to cycle the relays.)
The car puts a load on the system based on the settings in the car, respecting the limit the HPWC passed it. If the car sees a higher voltage drop when it loads the circuit up, it'll reduce the current it is drawing to hopefully prevent heat buildup elsewhere from becoming dangerous.
“Pulling” and “using” are the same thing to me, when it comes to electrical current. The dial inside the wall connector sets the max, and the car’s onboard charger pulls what it needs, up to the max communicated from the wall connector, but also not more than you configure in the car.
Nothing simple. I think there are three options: Plug in a car that can do more than 48A and see what the car reports the limit at, pull the front panel and check the position of the rotary dial, or use an O-Scope and probe to determine the duty cycle on the pilot signal and compare to J1772 standards.
karpetkutter
Member
That part is only required if the conduit enters from the top. Tesla also recommends it if the wires enter from the rear and are over a certain size, I believe.
Yep, looks like your electrician installed a disconnect for the wall connector. My guy did the same. Just cut the power to the wall connector and take the top cover off to see what the dial is set to. As others have mentioned the wall connector should be set to the amps for the circuit it’s connected to. You should definitely read the manual.
eprosenx
Active Member
Interesting. I am not sure why the disconnect was required. I do not know of any NEC requirement for this, though your local jurisdiction may have additional rules.
As others have said, the easiest way to check is to take the cover off and look at the rotary dial setting and compare it to the table in the manual which tells you what the different positions mean. It only sets what it will "tell" the car is the max it can support. You can then also tell the car from the dashboard touchscreen to use even less than that if you want to. And the car can and will often draw less than either of those numbers if it is ramping up the charge slowly or the battery is nearing capacity...
Note that you need the "security torx" head screwdriver bits to take the cover off. There is one screw on the bottom and then some careful prying of the plastic cover required, plus then about 8-12 additional torx screws to take off. Just be careful not to mess up the rubber seal under that layer of plastic since it is the waterproofing. Make sure it is re-seated properly when you re-install.
Feel free to take detailed pictures of what you see and we can take a look to see how good the install was. ;-) I would also be interested to see what the inside of that disconnect switch looks like (make sure the metal box was bonded to ground). Shut off the breaker inside of course before tearing open the disconnect switch.
I just installed my wall connector for my upcoming M3 just a couple weeks ago myself so I am well versed in this. ;-)
P.S. If indeed this is on a 60 amp breaker and the wire is sufficiently sized and the disconnect does not have fuses smaller than 60 amps and you are going to be only using this with a Model 3 then there is no way the car can pull more than 48 amps (which is the 80% derate for a 60a breaker) so you won't have any issues even if the dial is set wrong (well, I guess if it is set too low it might charge slowly). But kudos to you for wanting to check - and I think it is a GOOD idea to make sure it was done properly. It is always wise to have electrical equipment installed fully correctly. If you later upgraded to a Tesla with a faster charger (like a Model S with the bigger charger) - or if a later homeowner bought a car that could charge faster - then they may run into this kind of "latent defect".
As others have said, the easiest way to check is to take the cover off and look at the rotary dial setting and compare it to the table in the manual which tells you what the different positions mean. It only sets what it will "tell" the car is the max it can support. You can then also tell the car from the dashboard touchscreen to use even less than that if you want to. And the car can and will often draw less than either of those numbers if it is ramping up the charge slowly or the battery is nearing capacity...
Note that you need the "security torx" head screwdriver bits to take the cover off. There is one screw on the bottom and then some careful prying of the plastic cover required, plus then about 8-12 additional torx screws to take off. Just be careful not to mess up the rubber seal under that layer of plastic since it is the waterproofing. Make sure it is re-seated properly when you re-install.
Feel free to take detailed pictures of what you see and we can take a look to see how good the install was. ;-) I would also be interested to see what the inside of that disconnect switch looks like (make sure the metal box was bonded to ground). Shut off the breaker inside of course before tearing open the disconnect switch.
I just installed my wall connector for my upcoming M3 just a couple weeks ago myself so I am well versed in this. ;-)
P.S. If indeed this is on a 60 amp breaker and the wire is sufficiently sized and the disconnect does not have fuses smaller than 60 amps and you are going to be only using this with a Model 3 then there is no way the car can pull more than 48 amps (which is the 80% derate for a 60a breaker) so you won't have any issues even if the dial is set wrong (well, I guess if it is set too low it might charge slowly). But kudos to you for wanting to check - and I think it is a GOOD idea to make sure it was done properly. It is always wise to have electrical equipment installed fully correctly. If you later upgraded to a Tesla with a faster charger (like a Model S with the bigger charger) - or if a later homeowner bought a car that could charge faster - then they may run into this kind of "latent defect".
eprosenx
Active Member
So I did some more research into this and I found a new section of the NEC I was not aware of. Section 625.
Among other interesting tidbits, it has this:
625.43 - "Disconnecting means - For equipment rated more than 60 amperes or more than 150 volts to ground, the disconnecting means shall be provided and installed in a readily accessible location. The disconnecting means shall be lockable open in accordance with 110.25."
I read that as you can put one of those wire cage covers on the breaker so it can be locked "off" (they cost a few bucks at Home Depot or Platt Electric), but I think this could very much be open to debate as to what type of disconnect they are asking for. I guess it all comes down to your AHJ (authority having jurisdiction). I suppose if your breaker panel is a long way away or not easily accessible I could see the local inspectors wanting a disconnect right next to the unit.
Really though I think it is pretty silly. There are no serviceable parts inside like there are with AC units. If it breaks, you have to replace the whole thing anyway... (and that should nearly never happen) So the value prop of a disconnect switch is dubious in my opinion for most residential installs.
I have a disconnect and mine is 50a. He said it wasn’t required, but it’s one of those AC disconnects that you pull out the blade part. They are about $10, so why not.
I don’t see 624.43 would apply. It’s 60a and 120v to ground for each phase.
I don’t see 624.43 would apply. It’s 60a and 120v to ground for each phase.
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