Some questions about 14-50 receptacles

[Sophias_dad]

I wasn’t home when they installed it, but I’m confident they did not use Romex. My garage walls are finished and painted white, so I was adamant about minimizing holes in my walls. They did run PVC conduit through a hole in the ceiling Sheetrock, straight down the wall into my TESLA Wall Connector. That is the only exposed conduit. Goes up into the attic space above the ceiling there and over into my third garage bay and down the exterior wall into my main panel.
(FYI: My home was constructed in 2021.)

I'm with you on minimizing holes, I'd also be minimizing conduit(!). I wouldn't necessarily be so confident that the electrician didn't just stick Romex through the conduit on each end of the run. Its not a super big deal, just another violation. I mean after four we know of, that's only 25% more violations

Note the violation I'm referring to is running a 60 amp circuit with Romex, not Romex through conduit which seems to be another point of contention. Its clearly not allowed in conduit that's being run outside, since outside is a 'wet' location and Romex isn't allowed there.

 

[Rocky_H]

Note the violation I'm referring to is running a 60 amp circuit with Romex,

Let's be clear in case someone is seeing this a little out of context. Using Romex for a 60A circuit is not by itself a violation. You're talking about using undersized wire. If the Romex is something really big, like 4 gauge or 2 gauge, it would be sufficiently sized for a 60A circuit and would be fine.

I wouldn't necessarily be so confident that the electrician didn't just stick Romex through the conduit on each end of the run.

But yes, I thought of that too. Just seeing that there is conduit on the visible walls before it goes up into the attic doesn't show what is inside the conduit.

 

[Sophias_dad]

Let's be clear in case someone is seeing this a little out of context. Using Romex for a 60A circuit is not by itself a violation. You're talking about using undersized wire. If the Romex is something really big, like 4 gauge or 2 gauge, it would be sufficiently sized for a 60A circuit and would be fine.


But yes, I thought of that too. Just seeing that there is conduit on the visible walls before it goes up into the attic doesn't show what is inside the conduit.

Thanks for the clarification. I did intend to write that 6 gauge Romex wasn't allowed for a 60 amp EV charging circuit.

 

[STS-134]

Let's be clear in case someone is seeing this a little out of context. Using Romex for a 60A circuit is not by itself a violation. You're talking about using undersized wire. If the Romex is something really big, like 4 gauge or 2 gauge, it would be sufficiently sized for a 60A circuit and would be fine.

Yep, that's what I have. 4/3 NM-B for the 60A WC circuit. Although:

I always put in better wiring than what I think I will ever be needeing. The cost usually is trivial. Why not? What if I get a different wall connector in the future?

I wonder if I should have done 3 gauge THWN instead of 4 gauge NM-B so I could go up to a full 100A (80A continuous) in the future. What I'm not sure about is whether the connections on the WC or my Hubbell 14-50 outlet will take 3 gauge wiring at all however.

 

[MattM24]

Yep, that's what I have. 4/3 NM-B for the 60A WC circuit. Although:

I wonder if I should have done 3 gauge THWN instead of 4 gauge NM-B so I could go up to a full 100A (80A continuous) in the future. What I'm not sure about is whether the connections on the WC or my Hubbell 14-50 outlet will take 3 gauge wiring at all however.

Here’s hoping that EVs get more efficient rather than less efficient in the future and this won’t be a concern.

 

[Art84]

Yep, that's what I have. 4/3 NM-B for the 60A WC circuit. Although:

I wonder if I should have done 3 gauge THWN instead of 4 gauge NM-B so I could go up to a full 100A (80A continuous) in the future. What I'm not sure about is whether the connections on the WC or my Hubbell 14-50 outlet will take 3 gauge wiring at all however.

14-50 outlet will never support more than 50 amps (this is what 50 is stands for in the name). So you don't need 3 o 4 gauge for such outlet. 3 gauge will not fit, 4 gauge... well maybe but it will be very tough setup.

WC contractors max can fit 4 gauge.
Most likely the future proof is overkill. Tesla vehicles supported 80A charging for short period of time, but quickly came to the conclusion that it's a waste of resources (two onboard chargers, thicker wires) and sounds like 48A max charge level is here to stay for a long time.

 

[mspohr]

Yep, that's what I have. 4/3 NM-B for the 60A WC circuit. Although:

I wonder if I should have done 3 gauge THWN instead of 4 gauge NM-B so I could go up to a full 100A (80A continuous) in the future. What I'm not sure about is whether the connections on the WC or my Hubbell 14-50 outlet will take 3 gauge wiring at all however.

I don't know that having high capacity level 2 charging is that useful. I usually only charge at about 32 amps even though my system is capable of higher rates. Charging only takes a few hours most of the time. Even when the battery is very low, it still completes charging overnight with time to spare.
I guess if you have special needs where you need to charge a depleted battery quickly the higher rate might be necessary but lower charging rates are more efficient with less stress on the system.

 

[STS-134]

14-50 outlet will never support more than 50 amps (this is what 50 is stands for in the name). So you don't need 3 o 4 gauge for such outlet. 3 gauge will not fit, 4 gauge... well maybe but it will be very tough setup.

Yeah I understand that the outlet will never support more than 50A non-continuous, but an outlet can easily be swapped out for a hardwired connection, and if I had 3 gauge wiring, I could easily put a 80A EVSE there. But it sounds like this would have caused issues installing the 14-50 outlet in the first place, unless I used connectors to convert the 3 gauge to either 4 or 6 gauge, which is more connection points and more potential points of failure.

WC contractors max can fit 4 gauge.

And that sounds like it would have caused issues on the other device as well.

Most likely the future proof is overkill. Tesla vehicles supported 80A charging for short period of time, but quickly came to the conclusion that it's a waste of resources (two onboard chargers, thicker wires) and sounds like 48A max charge level is here to stay for a long time.

Well Lucid/Rivian are still doing it. And larger vehicles like the Cybertruck may use it and even the F-150 Lightning with the extended range battery, also a very inefficient vehicle, uses a 80A OBC. You can't really fight physics and it requires a certain amount of energy to push through the atmosphere. If you want a bigger car, it's going to need a bigger battery and to charge the bigger battery in a reasonable amount of time, it's going to need an 80A OBC.

I don't know that having high capacity level 2 charging is that useful. I usually only charge at about 32 amps even though my system is capable of higher rates. Charging only takes a few hours most of the time. Even when the battery is very low, it still completes charging overnight with time to spare.
I guess if you have special needs where you need to charge a depleted battery quickly the higher rate might be necessary but lower charging rates are more efficient with less stress on the system.

I don't think it's more efficient on Teslas, but that's because Teslas run the entire car's computer when the car is charging, which saps somewhere between 100-300W from the system the entire time.

 

[mspohr]

I don't think it's more efficient on Teslas, but that's because Teslas run the entire car's computer when the car is charging, which saps somewhere between 100-300W from the system the entire time.

Some time ago, someone tested charging current vs battery charge on Tesla Model S and came up with the most efficient charge rate being 24 to 32 amps. This gives between 5.7 kW and 7.7 kW at 240v. Higher currents incur exponentially higher I2R losses through all of the wiring as well as extra heat in the charger.

 

[STS-134]

Some time ago, someone tested charging current vs battery charge on Tesla Model S and came up with the most efficient charge rate being 24 to 32 amps. This gives between 5.7 kW and 7.7 kW at 240v. Higher currents incur exponentially higher I2R losses through all of the wiring as well as extra heat in the charger.

Interesting. Was there a table/graph given? How much less efficient was it at 48A vs 24-32A? And I wonder if this also applies to the Model 3 or if increasingly power hungry computers (even the Atom may consume more power than the old Model S computers but specially the Ryzen CPU) have pushed the most efficient point higher. Although whatever the efficiency drop is, it's probably not enough to make me want to adjust the charging current on my car.

 

[davewill]

Yep, that's what I have. 4/3 NM-B for the 60A WC circuit. Although:

I wonder if I should have done 3 gauge THWN instead of 4 gauge NM-B so I could go up to a full 100A (80A continuous) in the future. What I'm not sure about is whether the connections on the WC or my Hubbell 14-50 outlet will take 3 gauge wiring at all however.

What would have made more sense would have been to run that 100a circuit to a subpanel and wire the WC and 14-50 from there.

 

[STS-134]

What would have made more sense would have been to run that 100a circuit to a subpanel and wire the WC and 14-50 from there.

Subpanel is in the garage wall to begin with so...

 

[mspohr]

Interesting. Was there a table/graph given? How much less efficient was it at 48A vs 24-32A? And I wonder if this also applies to the Model 3 or if increasingly power hungry computers (even the Atom may consume more power than the old Model S computers but specially the Ryzen CPU) have pushed the most efficient point higher. Although whatever the efficiency drop is, it's probably not enough to make me want to adjust the charging current on my car.

After varying between 4 charge levels several times from dozens of charging sessions at 8, 24, 36, and 48 amps the results are a little surprising to me.

At 8 amps it recovers the 15% charge in 6 hours +/- 10 minutes with an efficiency of 73-81%
At 24 amps it recovers the 15% charge in 2 hours +/- 10 minutes with an efficiency of 76-88%
At 36 amps it recovers the 15% charge in 1 hour 20 minutes +/- 5 minutes with an efficiency of 97-99%
At 48 amps it recovers the 15% charge in 1 hour 5 minutes +/- 5 minutes with an efficiency of 70-77%

Lots of information in different threads.
Here's one:

Most efficient charging level

Sorry for the TL;DR Over the last few months, I've been curious about charging efficiency for my Model 3P and so I decided to do a small test: My wife has a very consistent driving schedule with it and so if you tracked from day to day and week to week, the charge level of the car (as well as...

teslamotorsclub.com

 

[Art84]

Well Lucid/Rivian are still doing it. And larger vehicles like the Cybertruck may use it and even the F-150 Lightning with the extended range battery, also a very inefficient vehicle, uses a 80A OBC. You can't really fight physics and it requires a certain amount of energy to push through the atmosphere. If you want a bigger car, it's going to need a bigger battery and to charge the bigger battery in a reasonable amount of time, it's going to need an 80A OBC.

Rivian is 48A though. Will see what's going to be with Cybertruck. I don't think they go more than 48A. Even if it have 150Kw battery, 48A is enough for overnight charging, considering you not charging fully drained battery to 100%. If you need faster - plenty of supercharges are around.
I have WC and charge at 32A and it's plenty... don't even need to use a full 48A.

 

[STS-134]

Rivian is 48A though. Will see what's going to be with Cybertruck. I don't think they go more than 48A. Even if it have 150Kw battery, 48A is enough for overnight charging, considering you not charging fully drained battery to 100%. If you need faster - plenty of supercharges are around.
I have WC and charge at 32A and it's plenty... don't even need to use a full 48A.

It's not so much about overnight charging as it is about keeping SoC set to 50% or lower for daily use to keep degradation low and needing to get up to some higher level ASAP because you decided to go on a trip on short notice. And the bigger the battery, the longer it takes. And in the future, it's likely to be about consuming the maximum amount of electricity when floating rates are cheap, likely in the middle of the day when solar panels are pumping out a lot of energy.

 

[Art84]

You forget that Tesla is all about efficiency. They even removed the mobile charger from the car and giving a $200 coupon for your to decide if you want mobile charger or wall connector. They analyzed that people almost don't use those mobile connectors so it's a waste for most of buyers. That's why I don't think they go back to 80A charging again, because they have plenty of data how people normally charge their cars. They rather make a car even more efficient so 100kw battery will be used more efficiently then increase a battery size, how GM, Ford and others are trying to do, but something does not work well.
Other EV car makers will have to become more efficient as well or they go bankrupt.

 

[STS-134]

You forget that Tesla is all about efficiency. They even removed the mobile charger from the car and giving a $200 coupon for your to decide if you want mobile charger or wall connector. They analyzed that people almost don't use those mobile connectors so it's a waste for most of buyers. That's why I don't think they go back to 80A charging again, because they have plenty of data how people normally charge their cars. They rather make a car even more efficient so 100kw battery will be used more efficiently then increase a battery size, how GM, Ford and others are trying to do, but something does not work well.
Other EV car makers will have to become more efficient as well or they go bankrupt.

People buying giant trucks don't really care about efficiency any more than people buying pickups care about gas mileage. It might be considered but it's not the first priority or you wouldn't be buying a giant truck in the first place. The market for trucks is different than the market for sedans.

 

[MattM24]

You forget that Tesla is all about efficiency. They even removed the mobile charger from the car and giving a $200 coupon for your to decide if you want mobile charger or wall connector. They analyzed that people almost don't use those mobile connectors so it's a waste for most of buyers. That's why I don't think they go back to 80A charging again, because they have plenty of data how people normally charge their cars. They rather make a car even more efficient so 100kw battery will be used more efficiently then increase a battery size, how GM, Ford and others are trying to do, but something does not work well.
Other EV car makers will have to become more efficient as well or they go bankrupt.

Nah, they’re just cheap and the coupon is damage control.

 

[STS-134]

Lots of information in different threads.
Here's one:

Most efficient charging level

Sorry for the TL;DR Over the last few months, I've been curious about charging efficiency for my Model 3P and so I decided to do a small test: My wife has a very consistent driving schedule with it and so if you tracked from day to day and week to week, the charge level of the car (as well as...

teslamotorsclub.com

To be fair though, the efficiency depends on the resistance of the wiring used as well as its length. My WC is connected to the panel with about 25-30' of 4 gauge NM-B. If they used 100' of 6 gauge THWN in their test setup, they're going to see much higher resistive losses.

 

[MattM24]

To be fair though, the efficiency depends on the resistance of the wiring used as well as its length. My WC is connected to the panel with about 25-30' of 4 gauge NM-B. If they used 100' of 6 gauge THWN in their test setup, they're going to see much higher resistive losses.

0.15ohm at 1000ft