Installing Tesla Wall Charger

[nietzj]

I’m planning to install a Tesla wall Charger and just wanted to double check my thoughts. The main is 125a and this charger can draw up to 48a continuously for well over 3 hours. If the main should trip at around 100a that’s a bit concerning when adding this size of a load. I plan to use #6 THHN for the current carrying conductors and a #10 for the ground. This will be in a 3/4” pvc so I know I’m fine landing this on a 60a breaker. Regardless, I never intend to charge at the full 48a out of fear of straining every connection throughout the system. I understand when setting up the app you can select the breaker size so a guy could just input this as a 50a or even a 40a breaker causing the charger to reduce the current. My question is for those who have installed/programmed these chargers should I use a 60a, 50a or even a 40a breaker?
I did ask a similar question last week, sorry for the redundancy, don’t want to screw this up.

 

[augie47]

there are a few "switches" on the market like this that help "shed" the load when necessary. You might give that some thought.

EVEMS which allows power sharing for full electric panels

Expand your full electric panel and add another high-power device such as a Type 2 EVSE Charger, a RV outlet, jacuzzi, steam shower, welder, A/C etc. No need to ask for more power from a already taxed grid. Use the power you already have more efficiently. Want to charge that Tesla in an...

simpleswitch.io

 

[curt swartz]

Why would a 125 amp breaker trip at 100 amps?

 

[curt swartz]

You need to do a proper load calculation to determine what the existing loads are in the panel.

 

[texie]

I’m planning to install a Tesla wall Charger and just wanted to double check my thoughts. The main is 125a and this charger can draw up to 48a continuously for well over 3 hours. If the main should trip at around 100a that’s a bit concerning when adding this size of a load. I plan to use #6 THHN for the current carrying conductors and a #10 for the ground. This will be in a 3/4” pvc so I know I’m fine landing this on a 60a breaker. Regardless, I never intend to charge at the full 48a out of fear of straining every connection throughout the system. I understand when setting up the app you can select the breaker size so a guy could just input this as a 50a or even a 40a breaker causing the charger to reduce the current. My question is for those who have installed/programmed these chargers should I use a 60a, 50a or even a 40a breaker?
I did ask a similar question last week, sorry for the redundancy, don’t want to screw this up.

To be compliant you need to do an Article 220 load calc for the existing service to determine if the service is adequate for whatever the load setting is of the charger. That said, I have wondered how the listing standards allow the charger setting to be simply set by the user in the app. This obviously will lead to people setting ratings that are not compliant for the circuit and OCPD and may not trip. For example, if the user sets the charger to a 60 amp breaker but the circuit and OCPD is 50 amp it may well not trip and cause the circuit to exceed the 80% rating of the circuit until, eventually, things fail.
FYI, a breaker does not trip at 80%.

 

[retirede]

That said, I have wondered how the listing standards allow the charger setting to be simply set by the user in the app. This obviously will lead to people setting ratings that are not compliant for the circuit and OCPD and may not trip. For example, if the user sets the charger to a 60 amp breaker but the circuit and OCPD is 50 amp it may well not trip and cause the circuit to exceed the 80% rating of the circuit until, eventually, things fail.

They don’t. The only units that can be compliantly installed on a circuit capable of less than the maximum rating must be deprecated by hardware switch that requires tools to access, or software not available to the user.

 

[texie]

They don’t. The only units that can be compliantly installed on a circuit capable of less than the maximum rating must be deprecated by hardware switch that requires tools to access, or software not available to the user.

Good to know. While I'm not a Tesla charger expert, I was led to believe otherwise by a number of people.

 

[curt swartz]

They don’t. The only units that can be compliantly installed on a circuit capable of less than the maximum rating must be deprecated by hardware switch that requires tools to access, or software not available to the user.

The current generation (3) of Tesla Wall chargers just require connecting your phone to the WiFi network it generates when first turned on. You then enter the IP address shown on the unit or scan the QR. The WiFi network stops broadcasting after 15 minutes. To get it to broadcast again you can either turn the breaker off and on or push the button on the handle for 5 seconds. Once connected you set the maximum charge rate based on the circuit installed.

The charge rate is actually set in the car but it can't be set for higher then the wall connector is set at.

 

[nietzj]

The charge rate is actually set in the car but it can't be set for higher then the wall connector is set at.

So a guy could just go ahead and throw in the 60a breaker and during the initial programming setup, use the hardwired/60a setting and then adjust the max charge rate from the vehicle? Would you have to set the charging rate from the vehicle every time you charge or would the car remember this chargers max rate? I assume most people would exit their vehicle, plug in the charger and walk away not giving it a second thought. Curious how that works if you alternate between home charging and a supercharger station?
I just want to charge at less than the full 48a, even at 32a the car would be fully charged in 8 hours while you sleep. I apologize for the dumb questions, this is the first time I’ve ever had to deal with a home charger.

Also, my mistake on assuming the 125a main would trip at 80%.

 

[nietzj]

Back to my original thought, wire this for max use, #6 on a 60a breaker, every thing is compliant. Now during new wall charger setup just say it’s on a 50a breaker and thus the max charge rate would be limited to probably 40a. That makes it less likely the HO could charge at the full 48a. Just trying to keep this safe.

 

[retirede]

So a guy could just go ahead and throw in the 60a breaker and during the initial programming setup, use the hardwired/60a setting and then adjust the max charge rate from the vehicle? Would you have to set the charging rate from the vehicle every time you charge or would the car remember this chargers max rate? I assume most people would exit their vehicle, plug in the charger and walk away not giving it a second thought. Curious how that works if you alternate between home charging and a supercharger station?
I just want to charge at less than the full 48a, even at 32a the car would be fully charged in 8 hours while you sleep. I apologize for the dumb questions, this is the first time I’ve ever had to deal with a home charger.

Also, my mistake on assuming the 125a main would trip at 80%.

Some cars let the user set the charge rate, some don’t. Teslas do.
The basic function is that the EVSE tells the car the maximum rate that can be supplied. As described above, the absolute maximum is set during commissioning and can be lowered by the user. The car will then charge at some rate not exceeding the value it gets from the EVSE. In the case of Tesla, a phone app can be used to lower the rate in either the EVSE or the car. If the commissioning step was carried out correctly, there is no way for the user to exceed the rating of the circuit.

No, the rate does not need to be specified each time. Most people just plug in and forget it. The car also supports a time schedule to accommodate TOU rates.

If you want to be ultra-conservative, you could wire the EVSE on a 60A circuit, but set it up for a 50A circuit during commissioning. The car will then never charge over 40A.

 

[nietzj]

If you want to be ultra-conservative, you could wire the EVSE on a 60A circuit, but set it up for a 50A circuit during commissioning. The car will then never charge over 40A.

Thank you, this sounds perfect for my situation. Even at 40a it should fully charge in 4-6 hours without stressing the distribution at any point.

 

[brycenesbitt]

My question is for those who have installed/programmed these chargers should I use a 60a, 50a or even a 40a breaker?
I did ask a similar question last week, sorry for the redundancy, don’t want to screw this up.

Install the 60A breaker and throttle it down in software.
The way Tesla does this gives me the shivers: a wrong click in the commissioning app and there's a time bomb: the car later demands more than the circuit can handle. Or, in some cases, a future car with faster charging does that.

I'd much rather have a DIP switch inside like other EVSE equipment.


The way it works with other EVSE equipment for non-Tesla SAE J1772 equipment is the EVSE sends a pulse down the pilot wire, which sets a current limit for the car. It's remarkably analog. The car chooses how much current to draw. The role of the EVSE is to set the pilot signal properly, do a GFCI check, then switch power on.
For non-Tesla situations you can also install an EVEMS with a clamp sensor on your main. You can set an total target power draw of house + charger, and the system will throttle the charging down to your target (likely you only have peak house power draw a few hours each day).
-
Faster is considered harder on the battery. So the smartest systems charge only as quickly as required to meet a certain charge level by a declared departure time.