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FAQ: Home Tesla charging infrastructure Q&A

Randy Spencer

Active Member
Mar 31, 2016
3,607
3,647
Alameda, CA
Did Tesla come thru with the money saving strategy of only allowing the Standard Range cars to charge at 32 amps no matter how big an EVSE you have? This was originally one of the differences but they also were not going to have glass roofs and they were to have cloth seats. I don't know anyone with any cars except long range ones so I have no one to ask about this.
 

A2be

Member
May 19, 2019
33
27
Denver, Colorado, USA, Sol3
Did Tesla come thru with the money saving strategy of only allowing the Standard Range cars to charge at 32 amps no matter how big an EVSE you have? This was originally one of the differences but they also were not going to have glass roofs and they were to have cloth seats. I don't know anyone with any cars except long range ones so I have no one to ask about this.
I wouldn't call it a "money saving strategy." It's just that, oftentimes, manufacturers very much want to differentiate their products into lower cost products for the most price sensitive buyers while having higher end (but very similar) products attract less price sensitive buyers. Just ordinary business practice to want to attract a wider set of buyers to one's product, and thus increase sales.

It is critically important for this strategy to work that the company tries to differentiate their products in feature/function, so that the high willingness-to-pay (WTP) buyers don't develop resentment against the low WTP buyers. This is standard marketing and pricing strategy.

Thus companies strategize how to make the differences salient. Setting an arbitrary (but lower) charge rate for Tesla chargers and the Model 3 SR/SR+ is just a really low-cost method to do a bit of this: they can just set a software limit even though a more capable charger hardware is in use and, voila, the high WTP buyers decide they would not want that "Neanderthal" feature of the slow(er) 32A charge rate. Win for the company; win for both kinds of buyers.
 

JL2025

New Member
Jun 1, 2021
3
0
USA
First, apologize if this is a repeat post. I thought I posted a few days ago but couldn't find it.

Anyway, my new house is prewired for EV charging. It looks like 8 gauge. It has 3 wires plus ground, and it's connected to dual 40A breakers. Good enough for my charging needs. The builder only left about 6-8 inches of wire and put the wire in a PVC electric outlet box. Before I have an electrician coming out, I want to know what my options are to install the Gen 3 Wall Connector so I don't sound that I am clueless (I know I am). So here it goes.....

If I want to hot wire in, the length of the wire will not be able to go around in the main unit before going to the terminals, but it's long enough if I can just go from the entry point straight to the terminals. What risk and likelyhood of such risk if I just simply have it run to the terminals directly? I don't know if it's a code issue or not. If it does need to go around inside the unit, would extending the wires by using wire nuts be acceptable?

If I want to make it into an outlet, and have the charger plug in, can that be done? There is so much information that I am not sure what parts are good (other than the outlet after reading the beginning of this thread). Also does the electrical box need to be switched out to metal?

I just hate to have to put in a new line at this point.

Thank you!
J
 

Cosmacelf

Well-Known Member
Mar 6, 2013
8,745
21,494
San Diego
First, apologize if this is a repeat post. I thought I posted a few days ago but couldn't find it.

Anyway, my new house is prewired for EV charging. It looks like 8 gauge. It has 3 wires plus ground, and it's connected to dual 40A breakers. Good enough for my charging needs. The builder only left about 6-8 inches of wire and put the wire in a PVC electric outlet box. Before I have an electrician coming out, I want to know what my options are to install the Gen 3 Wall Connector so I don't sound that I am clueless (I know I am). So here it goes.....

If I want to hot wire in, the length of the wire will not be able to go around in the main unit before going to the terminals, but it's long enough if I can just go from the entry point straight to the terminals. What risk and likelyhood of such risk if I just simply have it run to the terminals directly? I don't know if it's a code issue or not. If it does need to go around inside the unit, would extending the wires by using wire nuts be acceptable?

If I want to make it into an outlet, and have the charger plug in, can that be done? There is so much information that I am not sure what parts are good (other than the outlet after reading the beginning of this thread). Also does the electrical box need to be switched out to metal?

I just hate to have to put in a new line at this point.

Thank you!
J

I believe the gen 3 WC has a rear entry, so you can place the unit right over the outlet box. I’m assuming the electrical box is in the wall, meaning flush with the wall, and not sticking out on the wall? A picture might help.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,660
7,951
Boise, ID
Anyway, my new house is prewired for EV charging. It looks like 8 gauge. It has 3 wires plus ground, and it's connected to dual 40A breakers. Good enough for my charging needs.
That is referred to as a double pole 40A breaker, by the way. And yes, that 8 gauge would be fine for a 40A circuit. You do have two options:
1. You could put a wall connector on it, and I think that would probably reach well enough, since the Gen3 wall connector has the wire connections right there on a back plate that is mounted on the wall, so it's very close.

2. Instead of a wall connector, you could put an outlet on that instead. Since there is not an outlet type specific to a 40A circuit, electric code does allow for 50A outlet types on 40A circuits. So with three conductors plus ground, you could put on a 14-50 outlet. (You would need to order the 14-50 adapter from Tesla) The charging cord that comes with the car will only draw 32A maximum, which is the proper level for a 40A circuit (can only draw 80% of the circuit rating).

Electric code does have one other irritating requirement about the outlet options though. It says that any outlet being installed for the purpose of electric car charging must use a GFCI breaker, which are annoyingly about $100. Wall connectors don't need that. So weigh your cost options, which are basically either $500 for the wall connector or $45 for the 14-50 adapter + $100 for the GFCI breaker.
 

tga

Supporting Member
Supporting Member
Apr 8, 2014
3,997
2,864
New Hampshire
Electric code does have one other irritating requirement about the outlet options though. It says that any outlet being installed for the purpose of electric car charging must use a GFCI breaker, which are annoyingly about $100. Wall connectors don't need that. So weigh your cost options, which are basically either $500 for the wall connector or $45 for the 14-50 adapter + $100 for the GFCI breaker.

A friend asked me to help install a Wifi-connected Chargepoint Home unit (to participate in his utilitiy's demand response program). The manual says:
Ensure the electrical panel supports a 240 V dedicated circuit with a new, dedicated, non-GFCI two-pole circuit breaker, in accordance with local codes and ordinances.

Note: If local codes require a GFCI breaker for plug-in installation, ChargePoint recommends a hardwire installation. We do not recommend using a GFCI breaker as the Home Flex has charging circuit interrupting device (CCID) protection. Using a GFCI breaker in the panel can cause nuisance tripping.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,660
7,951
Boise, ID
A friend asked me to help install a Wifi-connected Chargepoint Home unit (to participate in his utilitiy's demand response program). The manual says:
Argh, can't get the rest to quote:
"Ensure the electrical panel supports a 240 V dedicated circuit with a new, dedicated, non-GFCI two-pole circuit breaker, in accordance with local codes and ordinances.

Note: If local codes require a GFCI breaker for plug-in installation, ChargePoint recommends a hardwire installation. We do not recommend using a GFCI breaker as the Home Flex has charging circuit interrupting device (CCID) protection. Using a GFCI breaker in the panel can cause nuisance tripping."

Yes, that all makes sense as they are trying to give all the options that avoid using that type of breaker. The GFCI circuit breaker is a stupid annoyance because EVSEs test for a proper ground connection by doing the very thing a GFCI is supposed to detect and prevent, so it frequently causes conflicts and trips. So if someone lives where they are not on NEC 2017 yet, you can use a normal circuit breaker and an outlet. Then it says if you do live in a place where that is required for outlets, (NEC 2017 or later) then go ahead and hard wire it instead, because that would then NOT require the GFCI breaker.
 
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JL2025

New Member
Jun 1, 2021
3
0
USA
I believe the gen 3 WC has a rear entry, so you can place the unit right over the outlet box. I’m assuming the electrical box is in the wall, meaning flush with the wall, and not sticking out on the wall? A picture might help.
Ah I didn't think of attaching a picture. Here it is.... Thank you!
 

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JL2025

New Member
Jun 1, 2021
3
0
USA
That is referred to as a double pole 40A breaker, by the way. And yes, that 8 gauge would be fine for a 40A circuit. You do have two options:
1. You could put a wall connector on it, and I think that would probably reach well enough, since the Gen3 wall connector has the wire connections right there on a back plate that is mounted on the wall, so it's very close.

2. Instead of a wall connector, you could put an outlet on that instead. Since there is not an outlet type specific to a 40A circuit, electric code does allow for 50A outlet types on 40A circuits. So with three conductors plus ground, you could put on a 14-50 outlet. (You would need to order the 14-50 adapter from Tesla) The charging cord that comes with the car will only draw 32A maximum, which is the proper level for a 40A circuit (can only draw 80% of the circuit rating).

Electric code does have one other irritating requirement about the outlet options though. It says that any outlet being installed for the purpose of electric car charging must use a GFCI breaker, which are annoyingly about $100. Wall connectors don't need that. So weigh your cost options, which are basically either $500 for the wall connector or $45 for the 14-50 adapter + $100 for the GFCI breaker.
Thanks! Do you know why Tesla instructs the wires to go around the right side before connecting?
 

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Cosmacelf

Well-Known Member
Mar 6, 2013
8,745
21,494
San Diego
Thanks! Do you know why Tesla instructs the wires to go around the right side before connecting?
No idea. But it is perfectly legit for you to get some THHN wire from Home Depot, wire nut them onto those wires in your flush mount electrical box and then you can reach inside the WC, assuming you plunk the WC on top of the connection box and use the WC rear entry.
 

FlatSix911

Porsche 918 Hybrid
Jun 15, 2015
6,878
6,500
Silicon Valley
Thanks! Do you know why Tesla instructs the wires to go around the right side before connecting?
Tesla probably recommends the right-side routing to provide a bit of strain relief.

I don't see a problem going directly from your wall box to the lugs without the right-side routing.
 

tga

Supporting Member
Supporting Member
Apr 8, 2014
3,997
2,864
New Hampshire
Argh, can't get the rest to quote:
Sorry! :)

Yes, that all makes sense as they are trying to give all the options that avoid using that type of breaker. The GFCI circuit breaker is a stupid annoyance because EVSEs test for a proper ground connection by doing the very thing a GFCI is supposed to detect and prevent, so it frequently causes conflicts and trips. So if someone lives where they are not on NEC 2017 yet, you can use a normal circuit breaker and an outlet. Then it says if you do live in a place where that is required for outlets, (NEC 2017 or later) then go ahead and hard wire it instead, because that would then NOT require the GFCI breaker.
"Mr/Ms Inspector, this 14-50 is for my parents RV. This 6-50 is for my welder. I would never think to charge an EV on them. What's an EV, anyway?" :)

My town is still on 2011. Or 2014, I forget. But it doesn't matter, because NH decided to mandate 2017 state-wide.

Honestly, with dual chargers, I'm installing a sub-panel with 80A capable. Because I can. When I do the garage/workshop addition, I'll probably run a 200A service to the garage. Because I can. (I'm channeling my inner Tim Allen, here)

No idea. But it is perfectly legit for you to get some THHN wire from Home Depot, wire nut them onto those wires in your flush mount electrical box and then you can reach inside the WC, assuming you plunk the WC on top of the connection box and use the WC rear entry.
Polaris connectors might be a better option. I'd definitely use them for 6ga. I haven't worked with 8 much. 10 I'd probably use wire nuts
 
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Rocky_H

Well-Known Member
Feb 19, 2015
6,660
7,951
Boise, ID
But it is perfectly legit for you to get some THHN wire from Home Depot, wire nut them onto those wires
😮 Uh, Whoa! Wire nutting seems really inappropriate for a high current connection like this. It's a 40A circuit, which probably needs something more solid to not have a bad resistive hot spot.
Polaris connectors might be a better option. I'd definitely use them for 6ga. I haven't worked with 8 much. 10 I'd probably use wire nuts
Yeah, for 120V 15 or 20A circuits, wire nuts would be OK, but I wouldn't like that for a 40A.
 
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Cosmacelf

Well-Known Member
Mar 6, 2013
8,745
21,494
San Diego
😮 Uh, Whoa! Wire nutting seems really inappropriate for a high current connection like this. It's a 40A circuit, which probably needs something more solid to not have a bad resistive hot spot.

Yeah, for 120V 15 or 20A circuits, wire nuts would be OK, but I wouldn't like that for a 40A.

Properly twisted together wires work just fine with 8 awg. You can buy wire nuts down to 6 gauge. Whatever. My point is that you can make a wire junction, combining the wires however you like, including Polaris connectors, in that rough in electrical box so that there is plenty of slack to get around the WC.

Not that this discussion matters, the guy who asked the question left a while ago…
 
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