20 or 30 amp breaker for tesla wall charger

[Rocky_H]

By code a 60a breaker can be used with #6 romex, provided it is not a continuous load situation that violates the 80% rule. This is because there is no such thing as a 55a breaker.

I really prefer people to just not say this, because they usually leave out the really REALLY vital piece of information, which leads people to getting an incorrect understanding of it and doing something dangerous.

This phrase I feel is not clear enough in explaining this:

provided it is not a continuous load situation that violates the 80% rule.

Most people will not get what you're implying here.

To be really clear, by doing this thing, with rounding up the breaker, IT DOES NOT MAKE IT AN ACTUAL 60A RATED CIRCUIT. The wire still only has a 55A rating, so that's like the lowest common denominator, and is the limit of the circuit rating. And since there is hardly any equipment that can be configured with the settings for a 55A circuit, this just isn't useful in the vast majority of cases.

So since mentioning this is going to cause a lot of people to misunderstand and do something dangerous, I prefer not to bring that up. I've seen way too many threads on this forum of people making this exact mistake.

 

[ATPMSD]

So since mentioning this is going to cause a lot of people to misunderstand and do something dangerous, I prefer not to bring that up. I've seen way too many threads on this forum of people making this exact mistake.

Can’t say I disagree as this is really not appropriate for EVSE Installations.

 

[SunnylandY]

Many valid points about GFCIs, 14-50 receptacles, #6 romex vs #6 thhn are interesing in their own right, but the question originally posed in this old thread is one that affects me and may be of interest to others... simply stated, how horrible is it to have a wall connector on a lower amperage circuit, say 30 or 20 amps, or even 15?

We have a vacation rental with 100 amp service. There is no AC and most stuff is gas; the only 240v loads are a hot tub and the dryer. I'm not sure how you do a valid load panel calculation in this scenario other than asking what happens if the hot tub (including heat), dryer, and ev charging are all happening at once along with some general loads like small kitchen appliances and whatnot.

Back to the original question though. Before we had the wall connector we used the mobile connector on a 14-50 outlet. I didn't like the way the cable got warm and found that dialing the charge rate on the car back to 16 amps kept it cool as a cucumber. Now with the wall connector we usually limit it to 24 amps to keep everything cool. Whether or not there's any value to keeping things cool, for us neither 16 or 24 amps seemed to present any significant limitation to lifestyle. At 16A that's 3.8 kw, if you arrive home by 9pm and leave at 7am that's enough to recover around 140 miles of driving. Isn't the average miles driven around 35 per day?

Because this is going into a vacation rental I don't want to base this assessment solely on my lifestyle, but it feels like a wall connector on a 20 or 30A circuit is still a very useful amenity. What am I missing?

 

[ATPMSD]

@SunnylandY

I would not worry about keeping things cool, I mean the wall connector is designed to run at 48-amps! As long as you use the correct wire you should be fine. Also, you should not be dialing back the charge rate in the car (if you are doing so) as a regular routine. As a vacation rental, the higher the available charge rate the better. The only disadvantage of the wall connector is it is a Tesla only solution, unless you opt for the version with the J1772 connector. I suggest this is more attractive than an “outlet.”

A 100-amp panel provides 80-amps of “continuous“ service. I suggest going with the wall connector, running 6/2 Romex, use an 50-amp breaker (GFCI not needed) and set the connector to a 50-amp circuit, this will give you a 40-amp charge rate. If you find the main breaker is tripping it will be very easy to swap out the 50-amp for a 40-amp breaker and change the connector to a 40-amp circuit.

 

[jcanoe]

Many valid points about GFCIs, 14-50 receptacles, #6 romex vs #6 thhn are interesing in their own right, but the question originally posed in this old thread is one that affects me and may be of interest to others... simply stated, how horrible is it to have a wall connector on a lower amperage circuit, say 30 or 20 amps, or even 15?

We have a vacation rental with 100 amp service. There is no AC and most stuff is gas; the only 240v loads are a hot tub and the dryer. I'm not sure how you do a valid load panel calculation in this scenario other than asking what happens if the hot tub (including heat), dryer, and ev charging are all happening at once along with some general loads like small kitchen appliances and whatnot.

Back to the original question though. Before we had the wall connector we used the mobile connector on a 14-50 outlet. I didn't like the way the cable got warm and found that dialing the charge rate on the car back to 16 amps kept it cool as a cucumber. Now with the wall connector we usually limit it to 24 amps to keep everything cool. Whether or not there's any value to keeping things cool, for us neither 16 or 24 amps seemed to present any significant limitation to lifestyle. At 16A that's 3.8 kw, if you arrive home by 9pm and leave at 7am that's enough to recover around 140 miles of driving. Isn't the average miles driven around 35 per day?

Because this is going into a vacation rental I don't want to base this assessment solely on my lifestyle, but it feels like a wall connector on a 20 or 30A circuit is still a very useful amenity. What am I missing?

If the Wall Connector is properly installed and configured for the provided 240V circuit rated from 15A up to 60A then the fact that the Wall Connector may feel warm to the touch of your hand while charging is not an issue. There is no benefit to lowering the charging amperage for the circuit. Lowering the charging amperage will extend the time needed to charge to the set charge limit. There is a fixed amount of overhead energy used while charging of ~230W. Charging as fast as the circuit supports will reduce the total overhead energy losses while charging.

(If I rented a property that was advertised as having a Tesla Wall Connector that I planned to use and later found that I could only charge at 12A, 16A or 24 A when the 240V circuit was capable of supporting charging at 32A/40A/48A I would enter a negative review. You don't have any way of knowing the renter's charging routine or needs. Don't jerk people around.)

 

[SunnylandY]

If the Wall Connector is properly installed and configured for the provided 240V circuit rated from 15A up to 60A then the fact that the Wall Connector may feel warm to the touch of your hand while charging is not an issue. There is no benefit to lowering the charging amperage for the circuit. Lowering the charging amperage will extend the time needed to charge to the set charge limit. There is a fixed amount of overhead energy used while charging of ~230W. Charging as fast as the circuit supports will reduce the total overhead energy losses while charging.

(If I rented a property that was advertised as having a Tesla Wall Connector that I planned to use and later found that I could only charge at 12A, 16A or 24 A when the 240V circuit was capable of supporting charging at 32A/40A/48A I would enter a negative review. You don't have any way of knowing the renter's charging routine or needs. Don't jerk people around.)

I appreciate the candid response, as I hadn't considered the possibility of Karens dinging me. The path of least resistance is to keep doing what everyone else is doing and not offer the charging facility at all. That seems to be just fine with most renters as they usually come in escalades

The perfect really is the enemy of the good.

 

[SunnylandY]

@SunnylandY

I would not worry about keeping things cool, I mean the wall connector is designed to run at 48-amps! As long as you use the correct wire you should be fine. Also, you should not be dialing back the charge rate in the car (if you are doing so) as a regular routine. As a vacation rental, the higher the available charge rate the better. The only disadvantage of the wall connector is it is a Tesla only solution, unless you opt for the version with the J1772 connector. I suggest this is more attractive than an “outlet.”

A 100-amp panel provides 80-amps of “continuous“ service. I suggest going with the wall connector, running 6/2 Romex, use an 50-amp breaker (GFCI not needed) and set the connector to a 50-amp circuit, this will give you a 40-amp charge rate. If you find the main breaker is tripping it will be very easy to swap out the 50-amp for a 40-amp breaker and change the connector to a 40-amp circuit.

I really need to avoid setting up a scenario where there is any reasonable chance the main could trip.

I have thought about the J1772 vs Tesla/NACS connector. We have a Tesla and that addresses 80% of the market. We could leave one of those Lectron adapters for someone who shows up with a Bolt or whatever, assuming nobody steals it. Maybe "those people" bring their own adapter.

This whole thing is starting to feel like a bad idea. Maybe I just put in a 30A outlet with a locking cover over it for my own use with my mobile connector and forget about making this an amenity for renters. Nobody is asking for it; I was trying to be a bit of an EVangelist/trendsetter here.

 

[davewill]

(If I rented a property that was advertised as having a Tesla Wall Connector that I planned to use and later found that I could only charge at 12A, 16A or 24 A when the 240V circuit was capable of supporting charging at 32A/40A/48A I would enter a negative review. You don't have any way of knowing the renter's charging routine or needs. Don't jerk people around.)

I hope you're joking. Someone is thoughtful enough to supply EV charging on a rental and you're going to look the gift horse in the mouth and complain that it wasn't fast enough for you?

 

[Rocky_H]

simply stated, how horrible is it to have a wall connector on a lower amperage circuit, say 30 or 20 amps, or even 15? [...] What am I missing?

That's a totally good option--not missing anything at all. I think that's one of the really nice advantages of the Tesla wall connector versus most other charging products in the market. It has amazing flexibility! You can install it on several levels of circuit without having to futz around with sometimes obscure outlet types or trying to get adapter plugs that Tesla sometimes doesn't sell. It's a good option.

There is no benefit to lowering the charging amperage for the circuit.

I would not worry about keeping things cool, I mean the wall connector is designed to run at 48-amps!

Well, I'm going to go ahead and stick with my disagreement on these because of Tesla's demonstrated history on this. They build charging equipment that they say is built for [number] rated level, and then there are frequently problems with higher than normal failure rates of things burning out or melting when people run them at this supposedly rated maximum level all the time, because Tesla seems to cut corners and be a little marginal about that. Many of the Gen1 UMCs had failures running at their maximum 40A level. And the old HPWCs had failures running at their maximum rated 80A level.

So from the previous data, I don't really trust their maximum rated amp levels for the long term lifetime of the equipment. I would rather use a wall connector on a 40 or 50A circuit so that it leaves some margin from what it is supposedly built for to stay a bit cooler, have less extreme thermal cycling, and last longer.

 

[terranx]

I appreciate the candid response, as I hadn't considered the possibility of Karens dinging me. The path of least resistance is to keep doing what everyone else is doing and not offer the charging facility at all. That seems to be just fine with most renters as they usually come in escalades

The perfect really is the enemy of the good.

I think simply noting the max available charging rates would get rid of most of those potential negative reviews (and I personally find it a bit ridiculous that someone would leave a negative review over a free charger not being fast enough).

I think 30A (24A continuous) would be a decent offering if you’re that concerned about tripping the main breaker (but it’s pretty unlikely you’d trip it even at 40 or 50A). That’s still about 6kW which is pretty similar to what a lot of commercial l2 chargers offer.

 

[Rocky_H]

I really need to avoid setting up a scenario where there is any reasonable chance the main could trip.

Yes, understandable, which is why it would be a good idea to do a load calculation. There are example ones you can go through online.

I have thought about the J1772 vs Tesla/NACS connector. We have a Tesla and that addresses 80% of the market. We could leave one of those Lectron adapters for someone who shows up with a Bolt or whatever, assuming nobody steals it. Maybe "those people" bring their own adapter.

Right. A J1772 addresses 100% of the market, so it is what I would go for for a rental property.

This whole thing is starting to feel like a bad idea.

Uh, what? Why?

Maybe I just put in a 30A outlet with a locking cover over it for my own use with my mobile connector and forget about making this an amenity for renters. Nobody is asking for it; I was trying to be a bit of an EVangelist/trendsetter here.

Well, then that brings it back down to addressing some smaller portion of the market instead of 100%. Many people don't bring charging cables with a wide selection of adapters to fit various random kinds of outlets. So a J1772 plug is what would really serve customers, because everyone with an electric car will always be able to use it.

 

[jcanoe]

A J1772 EVSE or a 30 amp dryer outlet with a description of any limitations would let renters who plan to charge their vehicle know what to expect. A Tesla owner who spots a Wall Connector in a rental listing photo without a written description is going to assume fast Level 2 charging unless otherwise documented.

 

[davewill]

Yes, understandable, which is why it would be a good idea to do a load calculation. There are example ones you can go through online.


Right. A J1772 addresses 100% of the market, so it is what I would go for for a rental property.


Uh, what? Why?


Well, then that brings it back down to addressing some smaller portion of the market instead of 100%. Many people don't bring charging cables with a wide selection of adapters to fit various random kinds of outlets. So a J1772 plug is what would really serve customers, because everyone with an electric car will always be able to use it.

Here is my take.

1. Take the time or spend the money to calculate what size charging you can safely support without concern for tripping breakers.
2. Install a hard-wired EVSE that supports that level of charging (or lower if there are budgetary concerns). J1772 would be best for general use, but if it costs too much or is too inconvenient for you, then install a Tesla Wall Connector.
3. Advertise exactly what you have: XXa J1772 or XXa Tesla Wall Connector.
4. Rest easy knowing you've done a good job. (Oh and profit....)

Considering that overnight charging is the most likely scenario in an overnight rental, any level of charging is useful and worth doing.

 

[jjrandorin]

Because this is going into a vacation rental I don't want to base this assessment solely on my lifestyle, but it feels like a wall connector on a 20 or 30A circuit is still a very useful amenity. What am I missing?

Its already been answered by some, but I will also chime in and say that, in my opinion, you are not missing anything. I also dont particularly share @jcanoe 's opinion on the specific topic of having charging but having a bit slower charging. People at a vacation rental will likely be charging overnight and running errands, and would likely really appreciate having charging there.

Half of them would probably just plug into a 120V outlet whether you wanted them to or not, so having an appropriate receptacle there would be great. The only thing is, I think I would do a J1772 adapter to cover 100% of all current EVs. Up to this point, choosing to be compatible with Tesla EVs is the defacto standard, especially since they were the only EV sold in real numbers.

That may not be the case 4-5 years from now, and you wont lose tesla renters by having an EVSE that is J1772 compatible vs having a Tesla specific one. If I was fortunate enough to be in your situation, I think I would put in a J1772 based EVSE (after having the load calculation done that @Rocky_H and @davewill both recommended).

Even 20amp 240V charging is meaningful for overnight parking, so I think it would be worth doing a hardwired EVSE even at 20amp if that is what makes sense from the load calculations.

 

[jcanoe]

If I'm on vacation with my Tesla vehicle I don't want someone making assumptions about my EV charging needs day or night. I would rent a different property as long as there was a nearby Supercharger or DC fast charger just to be done with it.

 

[davewill]

If I'm on vacation with my Tesla vehicle I don't want someone making assumptions about my EV charging needs day or night. I would rent a different property as long as there was a nearby Supercharger or DC fast charger just to be done with it.

Go big or go home, eh? I think you're missing the entire premise here. He's concerned that he might only have capacity for a lower amperage connection, and wants to know whether it would still be worth doing. Do you really mean that he shouldn't put in anything if he can't go whole hog?

 

[GtiMart]

I am currently renting a condo in Florida and it bums me that there's no way to charge there and virtually no j1772 around. I have to drive 20min to get to the nearest supercharger. I would love any charging, even 10A...

 

[jjrandorin]

If I'm on vacation with my Tesla vehicle I don't want someone making assumptions about my EV charging needs day or night. I would rent a different property as long as there was a nearby Supercharger or DC fast charger just to be done with it.

you are effectively saying:

"I would rather drive to a local supercharger to charge, rather than plug in, because I think this charging plug is too slow in the offered property". I would put forth that the specific thought process you are putting forth here would be in the VAASSST minority it relates to EV owners.

Most would just be happy there is some charging on property where they are, and that they dont have to make any arrangements other than plug in where they will be sleeping.

 

[SunnylandY]

Use cases for EVs seem to rely on a few reasonable behavioral assumptions. If someone's lifestyle involves driving 300 miles a day, coming home every night at 2am and leaving again at 5am it isn't my place to judge, but even 60 amps isn't going to be much help. I question whether that person would even be interested in driving an EV, why they would bother renting my place, and more importantly whether I even want you renting my place. It's a vacation home, not a supercharger.

 

[jcanoe]

Go big or go home, eh? I think you're missing the entire premise here. He's concerned that he might only have capacity for a lower amperage connection, and wants to know whether it would still be worth doing. Do you really mean that he shouldn't put in anything if he can't go whole hog?

OP stated "Before we had the wall connector we used the mobile connector on a 14-50 outlet. I didn't like the way the cable got warm and found that dialing the charge rate on the car back to 16 amps kept it cool as a cucumber." Assuming this install was up to code there is a 40A or 50A 240V charging circuit. Now that the 14-50 receptacle has been replaced with a Wall Connector the circuit should be able to support charging at 32 amps as with the 14-50 and Mobile Connector, possibly 40 amps if this is a 50A circuit. "I did not like the way the cable got warm" is not a valid way to measure the temperature of the cable, connector or receptacle nor is it a good reason to limit the charging to 16 amps.

The OP is free to do what they want with their property. I'm free to take my vacation money and rental business elsewhere. I also would not consider a rental where I could not control the thermostat or if there was a timer on the water heater.