Wire size for wall charger

[GP1200X]

The maximum amperage using THHN No. 6 wire (THHN wire being rated for 90C/194F), in this installation, would be determined by the temperature limit of the circuit breaker. A residential breaker will be rated for up to 60C (140F) or 75C (167F). Assuming the breaker is rated to 60C (140F) then a 55A limit would apply.

The Chargepoint EVSE can be set to a maximum of 50A. This is under the 55A limit and well within the 80% rule for EV charging for a 70A circuit. In this installation No. 6 THHN when used with a 70A (60C rated) breaker can support the Chargepoint EVSE set to operate at 50A.

Thanks!

I think all residential breakers are rated up to 75 degrees C. 6 gauge wire in conduit (THHN) is rated to 65A at 75 degrees C.


Your numbers aren't being done correctly, but I think you're accidentally coming out to the right answer.


So I think this is one of those odd examples where you do get to use the "round up rule" in NEC. The numbers look weird, but I think it's being followed correctly.

As I mentioned above, the limitation for 6 gauge THHN is 65A as the maximum rating limitation of the circuit. Continuous load can only be 80% of that, which is 52A. So that's where they get the 50A setting, which properly fits within it. But to have a 65A rated circuit, you generally can't find a breaker that is exactly 65A. So code allows a next sized up reasonably available breaker size, which would be 70 or 80. BUT THAT DOES NOT MAKE IT A 70 OR 80 AMP RATED CIRCUIT! It is still limited by the wire, so it's a 65A circuit.

Great! I get it and thought that might me the reasoning but never saw anyone ever acknowledge or set one up that way. I used a 60 amp to test but ordered a 70 amp breaker so I can push it to 50 amps which is the models limit. Every little bit helps. What surprized me was the price of the 70 amp versus the 60 amp Siemans .....6x the price at HD and Lo, but happened to find a new Siemans one for $30 elsewhere.
All set up, activated and finally finished. Now just waiting for new EV if it ever shows up.

 

[Vio1x]

I've got a question for the group. I just installed my Tesla Gen 3 Charger and had a question about the breaker.
I have a 100 amp breaker and 3 awg wire connected to my charger.
Question: is it okay (and will it pass inspection) with the above 100amp breaker with 3 awg wires?

I know the above is overkill, but its what I had so I used it. I recently moved my electrical panel and upgraded to 200 amp service. My electrician installed 3 awg wire between the two panels (old 100amp to the new 200 amp panel) while I rewired the new panel. I finished moving all the wires over to the new panel and had more than enough length of the 3 awg wire so I installed the charger to that. I had ordered a 60amp breaker and was going to install it, but it wont accept the large 3 awg wire, so now im wondering if I shouldnt bother and leave the 100amp breaker I currently have installed. Any advise?

 

[Art84]

I've got a question for the group. I just installed my Tesla Gen 3 Charger and had a question about the breaker.
I have a 100 amp breaker and 3 awg wire connected to my charger.
Question: is it okay (and will it pass inspection) with the above 100amp breaker with 3 awg wires?

I know the above is overkill, but its what I had so I used it. I recently moved my electrical panel and upgraded to 200 amp service. My electrician installed 3 awg wire between the two panels (old 100amp to the new 200 amp panel) while I rewired the new panel. I finished moving all the wires over to the new panel and had more than enough length of the 3 awg wire so I installed the charger to that. I had ordered a 60amp breaker and was going to install it, but it wont accept the large 3 awg wire, so now im wondering if I shouldnt bother and leave the 100amp breaker I currently have installed. Any advise?

Interesting... I wonder how you were able to connect 3AWG to the wall connector since the max wire size the contactor can fit is 4 AWG.
Not sure about the inspection, but from the code perspective it's acceptable to use 100A breaker for 3 AWG wire. So in your example, it will be a wall connector that will pull 48A max

 

[MY-Y]

I don't think the HPWC is rated for a breaker larger than 60A, nor a wire bigger than 4 gauge.

 

[Rocky_H]

I have a 100 amp breaker and 3 awg wire connected to my charger.
Question: is it okay (and will it pass inspection) with the above 100amp breaker with 3 awg wires?

No. You need to match the breaker to the appropriate setting of the amps of the circuit you set in the wall connector configuration. 60A is the max.

https://www.tesla.com/sites/default/files/support/charging/Gen3_WallConnector_Installation_Manual.pdf

I know the above is overkill, but its what I had so I used it.

Uh, no. That's not what overkill is. This isn't like, more than what you need so it's a good thing. It's the opposite of that. Oversizing breakers is dangerous.

 

[Art84]

No. You need to match the breaker to the appropriate setting of the amps of the circuit you set in the wall connector configuration. 60A is the max.

Not really. Setting in the wall connector is just to make sure that it will not pull more power than the breaker is set for the line. Since his line can handle more than 60A he can just set the max setting in wall connector and use it just fine.

 

[iluvmacs]

Not really. Setting in the wall connector is just to make sure that it will not pull more power than the breaker is set for the line. Since his line can handle more than 60A he can just set the max setting in wall connector and use it just fine.

... except for the part where components inside the WC are not rated higher than 60A, so a fault current of, say, 90A could be dangerous and would not trip the breaker.

 

[qdeathstar]

Interesting... I wonder how you were able to connect 3AWG to the wall connector since the max wire size the contactor can fit is 4 AWG.
Not sure about the inspection, but from the code perspective it's acceptable to use 100A breaker for 3 AWG wire. So in your example, it will be a wall connector that will pull 48A max

You just trim off a few of the strands and in slides right in *

*not actual events

 

[qdeathstar]

... except for the part where components inside the WC are not rated higher than 60A, so a fault current of, say, 90A could be dangerous and would not trip the breaker.

The fault current will be closer to 22000 amps, at least. It is the breakers responsibility to provide over current protection, not the evse, which is why the breaker needs to be set at the correct current for the evse settings.

 

[mspohr]

I thought the breaker was sized to protect the wire, not the device connected to it.
Lots of little wall warts connected to 15 amp breakers.

 

[Vio1x]

Interesting... I wonder how you were able to connect 3AWG to the wall connector since the max wire size the contactor can fit is 4 AWG.
Not sure about the inspection, but from the code perspective it's acceptable to use 100A breaker for 3 AWG wire. So in your example, it will be a wall connector that will pull 48A max

it fit into the charger just fine. The model 3 SR + will only actually pull 32amps max.

 

[Vio1x]

I thought the breaker was sized to protect the wire, not the device connected to it.
Lots of little wall warts connected to 15 amp breakers.

That was my understanding. My car will only pull 32amps. Even if there is a fault and it pulls more, the 3 gauge wire can handle it. If it pulls more than 100amps the breaker will trip.

My understanding is the danger lies when you use too large breakers on conductors that can't handle it (example 30 amp breaker on 14/2 wire). The wire could overheat and cause a fire. In my scenerio, im running 3 gauge wire (rated for 100 amps) terminating at a 100 amp breaker. Im normally only running about 32% of the capacity of the wire and breaker. Where is the danger?

 

[ucmndd]

Breakers protect conductors. There is nothing wrong with installing a device on a circuit that draws less than the amperage rating of the circuit.

As another poster said upthread, it’s not the 15 amp breaker’s job to protect your 5 watt phone charger from internally shorting itself and melting. That’s Underwriters Laboratories’ job.

 

[qdeathstar]

I thought the breaker was sized to protect the wire, not the device connected to it.
Lots of little wall warts connected to 15 amp breakers.

Both. Well, it won’t protect the device, by the time the breaker detects the fault the device let the smoke out…

But in anything with a motor in it, for example, the breaker will detect a fault from a stalled/seized motor and trip before the motor ignites into a ball of flames.

 

[ucmndd]

Both. Well, it won’t protect the device, but it will possibly detect the fault comming from the device.

Can you cite the section of code that would require an EVSE to be installed on a circuit/breaker that precisely matches its output (i.e. not oversized)?

 

[TBrownTX]

Lots of little wall warts connected to 15 amp breakers.

Agree, our houses are filled with oversized breakers.

Tim

 

[howardnj]

I used a NJ Licensed electrician from Tesla's recommended list. After they answered all my questions I had them install my HPWC in my garage and the 100 amp sub panel with a 150 ft run from my basement 200 amp panel. I qualified for the NJ PSE&G $1500 rebate. Very happy and no problems.

 

[Art84]

By the way breakers are designed to disconnect in two scenarios: 1. short circuit 2. overcurrent

The first happens immediately once your hot wire touches the neutral, or two hot wires (for 220v setup) touch each other. No matter what breaker amperage or thickness of the wire connected, it just immediately trips off. The second scenario is a slower process... in case of overcurrent, breaker begins to warm up, and when it reaches a certain temperature - it trips off. The primary goal of the breaker in the second scenario - disconnect the circuit to avoid overheating the connected wire. The breaker for 60A will not trip off immediately under the load of 80A for example, it will take some time.
So for the example above: if a wall connector unexpectedly has a short circuit inside - the breaker trip off immediately even if it's connected to 100A breaker line. And the second scenario, overcurrent for the wall connector - is hardly possible, just because it's not the wall connector that controls the current - it's a Tesla onboard charger that decides how much to pull from the grid. The setting of Amps in Wall Connector just informs Tesla onboard charger about the max current limit for the connected circuit that the onboard charger should not exceed. And that charger itself is not designed to pull more than 48A, and in the case of the Model 3 standard range, it's a 32A. And even if something goes wrong, the vehicle and wall connector have so many sensors that continuously monitor the charging session, it will immediately reduce or completely stop the charging process.

So, connecting Wall Connector with 3AWG and 100A breaker with setting up Wall Connector to 60A settings - is a completely safe setup.

 

[jcanoe]

I am still curious how it is possible to connect #3 wire to the Wall Connector mounting block as #4 is the largest supported wire gauge.

 

[andaconda]

I am still curious how it is possible to connect #3 wire to the Wall Connector mounting block as #4 is the largest supported wire gauge.

He cut off a couple strands to make it fit!