FAQ: Home Tesla charging infrastructure Q&A

[ModelS8794]

I see there is a minimum 18 inches above the ground for installing an outlet. Is there a maximum height as well? I think I'd like to have the outlet well out of the kids' reach, would there be any reason NOT to install the outlet 6 feet or so above the floor?

 

[dhrivnak]

I do not believe so. The 18" is to guard against flooding as water can ruin most outlets. So higher is fine.

 

[spatterso911]

Thanks again FlasherZ and MKnox. This is a great inservice!

 

[gtimbers]

Does the Tesla have a "smart" charging system? By this I mean does it monitor the voltage drop and restrict current flow accordingly. Owners report that the current ramps up slowly. I assumed this is to benefit the battery, but it could additionally be due to the charging system checking voltage drop. Do you have any knowledge of this?

 

[FlasherZ]

I see there is a minimum 18 inches above the ground for installing an outlet. Is there a maximum height as well? I think I'd like to have the outlet well out of the kids' reach, would there be any reason NOT to install the outlet 6 feet or so above the floor?

There is no maximum height in the US NEC; however, the ADA requires outlets to be no higher than 48-54" if you're in a commercial setting. The NEC requires the "disconnect means" to be "accessible" for a plug-and-cord connected EVSE, which typically means 7' or below.

I've found most electricians prefer to install them at 48". I've added this question to the FAQ.

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Does the Tesla have a "smart" charging system? By this I mean does it monitor the voltage drop and restrict current flow accordingly. Owners report that the current ramps up slowly. I assumed this is to benefit the battery, but it could additionally be due to the charging system checking voltage drop. Do you have any knowledge of this?

I have not seen anyone report that the car limits current or disables charging due to voltage drop -- then again, I haven't seen a voltage drop over 5% or so yet.

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I added a note on the OESC requirements for a disconnect to be "within sight and accessible" to the EVSE gear. This means that those of you in Canada will need to have a subpanel or disconnecting switch near your HPWC. In some jurisdictions in the US, the requirement for "readily accessible" means the same thing -- in others, having it in the same building is fine.

 

[Electric1]

Thank you FlasherZ. Your service in keeping us safe and from becoming public menaces is truly appreciated

 

[mknox]

I added a note on the OESC requirements for a disconnect to be "within sight and accessible" to the EVSE gear. This means that those of you in Canada will need to have a subpanel or disconnecting switch near your HPWC.

86-306 in the OESC caught my eye with respect to the labeling requirements for outlets, and that 120v outlets have to be dedicated 20 amp circuits. (In Canada, 120v circuits are more typically 15 amp.) This means that technically, your not supposed to plug the UMC with NEMA 5-15 adapter into a "regular" 15 amp outlet!

 

[FlasherZ]

86-306 in the OESC caught my eye with respect to the labeling requirements for outlets, and that 120v outlets have to be dedicated 20 amp circuits. (In Canada, 120v circuits are more typically 15 amp.) This means that technically, your not supposed to plug the UMC with NEMA 5-15 adapter into a "regular" 15 amp outlet!

...and a single receptacle (no duplex!) at that... seems a bit overkill.

 

[agileone]

For Quebec based owners, Hydro-Quebec has produced guides for charging infrastructure, both public and private :

english : http://www.hydroquebec.com/transportation-electrification/pdf/technical-installation-guide.pdf
francais : http://www.hydroquebec.com/electrification-transport/pdf/guide-technique.pdf

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I am tempted to replicate the setup ckessel has documented here with a tool balancer to hang the cable from the ceiling

Any insights on why not to ?

 

[FlasherZ]

I am tempted to replicate the setup ckessel has documented here with a tool balancer to hang the cable from the ceiling

Any insights on why not to ?

Not really, although technically it's against code in both the NEC (unless it hangs down to 48" from the floor) and the OESC referenced earlier (86-404, max height 1.2m off the floor). Not sure if Quebec has the same limitations. That said, I doubt you'll find someone who has an issue with it. I rather like the idea of that installation.

 

[Duckjybe]

Great info!

A couple questions: For a 100A garage sub panel (in Ontario), am I required to use an electrician? Do I need a building permit? ESA inspection should be done but is it ok if no electrician was used?

 

[FlasherZ]

Great info!

A couple questions: For a 100A garage sub panel (in Ontario), am I required to use an electrician? Do I need a building permit? ESA inspection should be done but is it ok if no electrician was used?

Unfortunately, I can't answer that but maybe mknox will know? In most areas in the US, you would need an electrical work permit and inspection, and as long as it was your own single-family residence (not a commercial building or leased/rented residence) you are permitted to do your own work. Check with your city hall or whatever local jurisdiction might handle the inspection (in the States, it's usually at the county level if outside of city limits).

 

[MikeK]

FlasherZ, thanks! This is a wonderful compilation of excellent information and I'm sure many people will appreciate it!

 

[mknox]

A couple questions: For a 100A garage sub panel (in Ontario), am I required to use an electrician? Do I need a building permit? ESA inspection should be done but is it ok if no electrician was used?

In Ontario, you can do your own wiring, but you are required to take out an ESA permit and it will be subject to inspections (and fees). You can't do wiring for someone else, and you can't do wiring for pay unless you are a licensed electrician. Good information here. From their web site: "Homeowners who are doing their own electrical installations should contact the Electrical Safety Authority at 1-877-372-7233 to arrange for an electrical inspection. These arrangements should be made up to 48 hours after the commencement of work".

A 100 amp sub-panel is pretty big, and you should check that your main service entrance equipment has the capacity to add this much load to it. (I wouldn't be able to... my home's main service is only 100 amp!)

You should also contact your local electricity utility regarding the load increase, and if you are upgrading your main service to support the 100 amp sub-service you must contact them and conform to their Conditions of Service (which should be posted on their web site).

The Ontario Electrical Safety Codebook is available, but not for free (details on the web site).

Hope this helps!

 

[Duckjybe]

Thanks for the information.

Let me run this config by you just to see if I am somewhat qualified to do my own electrical (I do have an Electrical Engineering degree but doesnt mean i am qualified like some people think)

I have a 200A service (but panel is full after this) 70A breaker in main panel. Connects through #3 T90 (black, white, green) wire run in 1 1/2" pvc conduit for 70ft run to attached garage sub panel (bonded neutral). Two breakers in sub panel. One 30A to 6-30R for Volt, and one 40A (just because i have one, or do I need 50A) breaker to 14-50R for Model S. Is this ok?

Model S P85 comes in March/Apr.!

 

[mknox]

I do have an Electrical Engineering degree but doesnt mean i am qualified like some people think

...and I've worked in the electric utility business for 33+ years and would say the same of me :wink: (We tend to stay on our side of the demarcation point and don't get involved in "behind the meter" activities).

My advice would be to consult with the ESA first. Section 8-104 of the Code talks to circuit loading and capacity, but you have to consider the EV chargers as a "continuous load" in calculations, and it also depends on how the other curciuts in your home are loaded. (Definition of Continuous: The calculated load in a consumer’s service, feeder, or branch circuit shall be considered a continuous load unless it can be shown that in normal operation it will not persist for (a) a total of more than 1 h in any two-hour period if the load does not exceed 225 A; or (b) a total of more than 3 h in any six-hour period if the load exceeds 225 A.)

You would need a 50 amp breaker to supply a 14-50 receptacle.

On a bit of a tangent, one of the things I've wondered about is the power factor of these EV chargers. Consumer meters don't record or factor in reactive power and billing is based only on kWh not kVAh, but if the power factor is "bad" enough, that would add current to the circuit...

 

[FlasherZ]

Let me run this config by you just to see if I am somewhat qualified to do my own electrical (I do have an Electrical Engineering degree but doesnt mean i am qualified like some people think)

The same applies to us all. As I've posted in the "what do you do?" thread, this is not my day job, but I have A LOT of experience with electrical work and it's a particular interest/passion of mine.

I have a 200A service (but panel is full after this) 70A breaker in main panel. Connects through #3 T90 (black, white, green) wire run in 1 1/2" pvc conduit for 70ft run to attached garage sub panel (bonded neutral). Two breakers in sub panel. One 30A to 6-30R for Volt, and one 40A (or do I need 50A) breaker to 14-50R for Model S. Is this ok?

A couple of points -- and all from the perspective of the US NEC (again, I can't speak to Canadian regulations, although I know they come close):

First in the US, you would not be permitted to bond/share your ground and neutral if the subpanel were installed after your jurisdiction's adoption of NEC 2005 (in most jurisdictions that happens between 2006-2009). You must run all 4 wires, although #8 ground would be fine for a 70A feeder.

Also, wire color becomes an issue. You mentioned T90, which I believe is the equivalent of THWN (single-conductor insulated wire), yes? If so, you also would not be permitted to remark a white T90 wire as a hot conductor, nor can you remark/use green as anything but an equipment grounding conductor (you couldn't use this for your bonded neutral/ground combination). You are permitted to remark white wires for hot only if they're part of a cable assembly (like NM-B).

As for the 40A/50A question, it's a matter of the load you intend to connect to it. Technically, (again in the US) having a 50A receptacle on a 40A branch circuit (sized for 40A in the wiring) is legal -- until you plug in a device whose nameplate demands a 50A circuit. In this case, it's confusing because the various adaptors of the UMC give it a different minimum ampacity rating based on which one you have. Combining NEC article 625's requirement that EVSE loads be considered continuous loads and the UMC's 40A rating with a 14-50 plug attached means that the device requires a 50A circuit. So you'd have to upgrade to a 50A breaker if you intend to plug the UMC into it.

Wire type, size, and raceway size are adequate (and the conduit is rather overkill as 1" PVC is fine for 3 #3's + #6 ground).

And as mknox said, because you're adding a significant load, it's time to redo those load calculations for your main panel to determine if you have the correct panel & service size. With 200A service in a reasonable-size single-family home you *should* be okay, but doing the calculations guarantees you're ok.

Model S P85 comes in March/Apr.!

Congratulations!

 

[Duckjybe]

FlasherZ: you would not be permitted to bond/share your ground and neutral

Sorry I was wrong about my config. 2 BL, 1 WH, and 1 Grn, WH and Grn not bonded. My Grn should have been uninsulated probably and is also #3 which is overkill.

I just double checked. A little unconventional maybe, but should be safe to add the Model S at 50A?

I will do load calculations for my main panel.

Thanks very much! This forum with its members from all walks of life and their expertise is absolutely invaluable!

mknox: I've wondered about is the power factor of these EV chargers. Consumer meters don't record or factor in reactive power and billing is based only on kWh not kVAh, but if the power factor is "bad" enough, that would add current to the circuit...

Hmm, now I'm going to have to go back to my engineering texts as I am very fuzzy on reactive power....26 years ago.

 

[FlasherZ]

Sorry I was wrong about my config. 2 BL, 1 WH, and 1 Grn, WH and Grn not bonded. My Grn should have been uninsulated probably and is also #3 which is overkill.

I just double checked. A little unconventional maybe, but should be safe to add the Model S at 50A?

The #3 ground is a bit big, but it's not a hazard in any way (as long as the box's lugs are rated for #3).

That looks good and should be safe, looks like you might need a new ground lug for the 14-50, or are the wires covering up an unused spot?

When you put the 14-50 wiring in, you may want to square it off a bit more into the corners of the box with 90 degree bends.

 

[mknox]

Hmm, now I'm going to have to go back to my engineering texts as I am very fuzzy on reactive power....26 years ago.

When asked, I always like to point to this small paper on Power Factor by the US DOE. I like the analogy of the horse pulling the railroad car!