New Tesla owner with questions

[ATPMSD]

@3sr+buyer

You noted the corrective actions, but let’s be clear:

An outlet on a circuit with other stuff on it that may be in use while charging.

Code violation, EV charging circuit must be dedicated

An outlet with poor contacts to the plug blades that result in excess heat during charging at high amperages.

Using such an outlet is foolish. It should not be used at all until it is fixed.

An outlet installed on a circuit that really cannot handle the amperage implied by the outlet

Code violation

 

[3sr+buyer]

Code violation, EV charging circuit must be dedicated

Lots of older houses have 5-15 outlets in the garage that are on circuits shared with other things. They were not code violations when built or installed, even though they would be in newer houses.

Also, someone buying a house may encounter code violations due to incorrect installation by a previous owner.

 

[Gauss Guzzler]

Correct, OP is not building/remodeling the garage so building code compliance is not a factor. They just need something that works with what they've got. Using an existing outlet for EV charging is never a "code violation" nor is using an outlet shared with other loads. Code only mandates that *new* installations intended solely for EV charging must be on dedicated circuits.

But speaking of building code, there is no such code requiring 20A outlets in a garage or anywhere else. The *circuit* should be 20A but the receptacles are only rated at 15A unless they have the distinctive T-shaped neutral. Typically, you can't use a breaker with a higher rating than the receptacle, but NEC makes this rare exception for 120V receptacles since there is no limit to the number of receptacles that can be installed on a single circuit.

 

[KYVolsfan]

It won't. But a 5-20 adapter can be used to get 120V 16A charging if you have a 20A circuit with a 5-20 outlet.

However, with any 120V household outlet, check whether there is anything else on the same circuit before charging an EV on it. If there is, then you may have to reduce the charging current so that charging while other stuff on that circuit is being used does not overload the circuit and trip the breaker.

But 240V charging is generally a lot more convenient for home charging. Also, at the slow charging rates of 120V charging, the charging efficiency is worse due to cost of the car being on while charging being a greater percentage of the energy drawn from the wall.

I’m most definitely not an electrician, so this may be very wrong, but would all the plugs in the garage be on the same circuit? I have 3 plugs, one on each wall. If they are on the same circuit, it will be difficult to get a dedicated one. Is this correct?

 

[MLXXXp]

but would all the plugs in the garage be on the same circuit?

It's easy enough to find out. Switch off the breaker and see which outlets go dead.

 

[ATPMSD]

Lots of older houses have 5-15 outlets in the garage that are on circuits shared with other things. They were not code violations when built or installed, even though they would be in newer houses.

Also, someone buying a house may encounter code violations due to incorrect installation by a previous owner.

210.17 Electric Vehicle Branch Circuit. An outlet(s) installed for the purpose of charging electric vehicles shall be supplied by a separate branch circuit. This circuit shall have no other outlets.

We can split hairs as to whether the word installed means only a newly run circuit, but there is a reason for what the code says. Owner’s call, of course.

 

[KYVolsfan]

It's easy enough to find out. Switch off the breaker and see which outlets go dead.

Good point. I don’t mind digging into plumbing issues, repairing things around the house, but electrical issues have always given me pause. But I shouldn’t be able to burn down the house by flipping a few switches.

 

[KYVolsfan]

210.17 Electric Vehicle Branch Circuit. An outlet(s) installed for the purpose of charging electric vehicles shall be supplied by a separate branch circuit. This circuit shall have no other outlets.

We can split hairs as to whether the word installed means only a newly run circuit, but there is a reason for what the code says. Owner’s call, of course.

Good point. I don’t mind digging into plumbing issues, repairing things around the house, but electrical issues have always given me pause. But I shouldn’t be able to burn down the house by flipping a few switches.

Ok, just checked and the breaker controls all 3 outlets in the garage and the electricity in my utility room.

Curious - is it unsafe to plug the Tesla charger into an extension cord? A heavy duty one, not a cheap Walmart cord.

 

[Gauss Guzzler]

@ATPMSD "Building code" only applies whilst "building".

@KYVolsfan Avoid extension cords whenever possible. First, there are the obvious doubts of quality/rating as you know, but also the Tesla charger has a temperature sensor in the plug to detect issues at the receptacle. This sensor will still work well to detect issues at the extension cord interface, but there's a possibility that an overheating receptacle could go unnoticed. And note that the receptacle is the most likely part of the system to overheat - not only is it usually the oldest and most worn component, but inadequately tightened wire terminal screws are a notorious source of overheating.

 

[ATPMSD]

“Building code" only applies whilst "building".

Nope. Also applies anytime you make a modification. This is why you have to pull permits when making modifications.

 

[Keninblaine]

The code requirements for EV charging are more strict due to the heavy duty cycle load over many hours during a charging session. If you are using a 120v receptacle that may be on a multi-receptacle circuit, and if putting the charging receptacle on a dedicated circuit is impractical, I would check to ensure that the other receptacles on that circuit are not in use while charging. But for piece of mind and to avoid an electrical fire burning down your house, I would seriously consider adding a dedicated charging circuit. The cost of proper home charging should be considered part of the cost of getting an EV in my opinion.

 

[Gauss Guzzler]

Nope. Also applies anytime you make a modification. This is why you have to pull permits when making modifications.

Building permits?

 

[3sr+buyer]

210.17 Electric Vehicle Branch Circuit. An outlet(s) installed for the purpose of charging electric vehicles shall be supplied by a separate branch circuit. This circuit shall have no other outlets.

We can split hairs as to whether the word installed means only a newly run circuit, but there is a reason for what the code says. Owner’s call, of course.

Lots of older houses were built before any "EV" sections of the electrical code existed. They did not suddenly become illegal when the allowed-by-code practices were no longer allowed-by-code, just like 1-15 (without grounding hole) outlets found in many older houses.

A more relevant example is that newer codes require an unshared 120V 20A outlet for each vehicle bay in the garage (210.11(C)(4)). But older garages buit before such a requirement did not become illegal, so EV drivers charging off of 120V outlets in older garages need to be careful about other stuff on the same circuit.

 

[3sr+buyer]

Ok, just checked and the breaker controls all 3 outlets in the garage and the electricity in my utility room.

What is in the utility room plugged into outlets controlled by that breaker?

Now that you know what is on the same circuit, if you do use 120V charging from a garage outlet, you know how much you may have to lower the amperage based on what else may be using that same circuit.

Longer term, it is more convenient and safer to get a dedicated 240V circuit for EV charging.

 

[ucmndd]

We can split hairs as to whether the word installed means only a newly run circuit

No, we can’t. When building code applies and when it is enforced is a very cut and dry thing. No hair splitting required.

 

[Keninblaine]

I worry when some people think that homes built prior to recent electrical code updates are exempt from updating their wiring for certain applications such as EV charging. If a home was wired before the advent of home EV chargers, and therefore doesn't have the necessary dedicated EV circuit(s), then a case could be made that no EV charging should take place until the necessary upgrades are made. A new requirement is being added to a home that wasn't built to handle that requirement. Just because a home has an outlet that accepts your charging cord doesn't mean that you should use that outlet.

As an another example of the importance of using caution with charging circuits, the attached link, at around the 8' 30" point, makes reference to problems experienced with many 14-50 NEMA installations. There are numerous brands of NEMA 14-50 receptacles available, such as at Home Depot and Amazon, that are code compliant for things like ovens etc. But only one or two, made by Hubbell and Kellems, are robust enough to handle the duty cycle of EV charging. They use better quality metal for connections, better screw connectors for capturing conductors, and use more heat resistant Bakelite rather than plastic for the housing.

I installed a NEMA 14-50 circuit in my garage a year ago and luckily found information about this (thanks YouTube) in time to make the correction by removing the inexpensive receptacle I purchased at HD and installing a Kellems which cost close to $100, about 3 times the cost of a cheaper unit I had purchased at HD. The HD unit was a common brand name (Leviton I believe), so I had assumed all products were suitable for any 14-50 circuit, so why pay $100 if one could be bought for $25? The devil is in the details, and can make the difference between a safe reliable charging circuit and a possible house fire caused by overheated circuit components.

 

[ATPMSD]

Let's also remember the 80% rule applies no matter what. If you plug in the MC into a 5-15 outlet it will pull 12A which is 80% of the 15A circuit rating. If anything else is powered by the same circuit you are in violation of the 80%.

Yes, you can dial-down the car but this not a recommended since there is no way to guarantee it will not change back. It is best to not look for ways to get around the rules, be safe with electricity.

 

[alexgr]

Curious - is it unsafe to plug the Tesla charger into an extension cord? A heavy duty one, not a cheap Walmart cord.

It is not "kosher". By rules of some Federal facilities, you might need to file a special permit application that will be followed by an inspection, etc. to use an extension cord for pretty much anything. For the people (not feds), UL listed 14-50 extension cords do exist, even 50A rated cords. For safety matters, you should make sure
(1) It is a real UL or ETL listed cord and
(2) There is absolutely no way something may damage it when it is plugged in.

 

[3sr+buyer]

I worry when some people think that homes built prior to recent electrical code updates are exempt from updating their wiring for certain applications such as EV charging. If a home was wired before the advent of home EV chargers, and therefore doesn't have the necessary dedicated EV circuit(s), then a case could be made that no EV charging should take place until the necessary upgrades are made.

That argues against the purpose of the Mobile Connector (or any other portable EVSE) with respect to road trips (or keeping it in the car "just in case"), since most of the possible places to plug it into would be installations from before the "EV" parts of the electrical code existed.

As an another example of the importance of using caution with charging circuits, the attached link, at around the 8' 30" point, makes reference to problems experienced with many 14-50 NEMA installations. There are numerous brands of NEMA 14-50 receptacles available, such as at Home Depot and Amazon, that are code compliant for things like ovens etc. But only one or two, made by Hubbell and Kellems, are robust enough to handle the duty cycle of EV charging. They use better quality metal for connections, better screw connectors for capturing conductors, and use more heat resistant Bakelite rather than plastic for the housing.

Actually, more than one or two. The Hubbell 9450A (and Bryant / Kellems versions) 14-50 outlet (but not their 6-50 outlet) has the more mistake-resistant wire clamps rather than screw down wire connections, but careful installation of screw down wire connections works. The big difference is that the very common Leviton outlets have steel half size contacts to the plug blades, leading to higher resistance and heat compared to the full size brass contacts in most other outlets. This can make them marginal heat-wise at around 30A, regardless of how careful the installation is.

 

[RayK]

Ok, just checked and the breaker controls all 3 outlets in the garage and the electricity in my utility room.

This is mostly the problem in my own garage; most of the outlets are on the same circuit breaker. In addition, on one wall there's an outlet which has it's own GFCI (ground fault circuit interrupter; a safety device to minimize electrocution - those red and black buttons between the outlets) breaker built in. For some reason, ALL of the other outlets on the same wall are daisy-chained with that GFCI outlet; meaning that all of the 5-15 outlets are protected by that single GFCI outlet. It is not recommended to power the Tesla mobile connector from an outlet which has GFCI protection, either at the main circuit breaker panel or built into an outlet. The reason being is that the mobile connector has it's own GFCI protection and there can be "false" power trips (i.e., main breaker switches off) because of the two competing systems. As is sounds like you have not had any problems concerning power interruptions, you probably don't have any GFCI breakers in that circuit. But just be aware that this can happen.

Curious - is it unsafe to plug the Tesla charger into an extension cord? A heavy duty one, not a cheap Walmart cord.

It is also not recommended to use an extension cord with the Tesla mobile connector. The reason being is that the Tesla NEMA plug adapter (the 120V / 240V plug which is inserted into the wall outlet) has a built-in temperature sensor. That sensor should be located near the wall outlet as that's the prime location where overheating can occur. If you use an extension cord, the sensor has now been moved far away from the outlet and it cannot monitor any heat which might happen. The temperature sensor has been designed to automatically lower the charge current of the mobile connector when excessive heat is detected at the wall outlet. Therefore, if you do use an extension, you may be negating a fairly important safety system.

That said, if you use a heavy duty extension cord AND monitor both connections (the extension cord/wall outlet and the extension cord/Tesla mobile connector) for overheating, you can charge your car. By "heavy duty" I mean a cord which has at least 12 gauge wire (AWG) if using the standard 5-15 outlet (max. of 12A). Important point: wire gauge numbers are lower in value for thicker wire (which can safely handle more current). A 14 gauge wire cannot safely deliver the amount of current that 12 gauge wire can. Get an extension cord that is just long enough to do the job. Purchasing a 100' cord when you only need 25' wastes your money AND can lower your charging power: longer cord generally means lower power delivered at the end. Doing this also prevents you from having to coil up any excess cord along the way. Using one of those extension cord reels that wind the entire length of the cord to keep things neat and orderly also means that you are going to heat up the wire if you pass any substantial current through it.