Home charging setup, challenging conventional wisdom.

[SSedan]

Aluminum really won't save a meaningful amount ofoney and will increase heat cycling concerns if you ever do run the circuit at 80amps.

My opinion on why Tesla says no aluminum on the HPWC is the expectation is the circuit will run 80% for hours on end and heat cycle. Aluminum's greater expansion can create issues with this.
A service line rarely if ever runs at 80% of rated and if it does not for long so the common use of aluminum there is less likely to be an issue.

 

[Glamisduner]

6awg Romex is rated for only 55A and would not support 48A continuous charging, despite having a 60A breaker. That's why I was stating 75deg rated, 6awg conductors, although you will have to have them in conduit. The 100ft length will produce a voltage drop of around 5V at 48A which is within the 3% recommendation that the NEC makes.

Ok so maybe a pair of 6awg runs would be ideal, but I'm pretty sure there is not supposed to be any breaks in the run too, so I'm still not sure what the electrician is thinking I would do when it's time for a second outlet in a different location. Maybe I should just do two outlets now.

actually the guy never came out to do the install, and i never heard back from him so I may be looking for a new electrician anyways

 

[GWord]

Ok so maybe a pair of 6awg runs would be ideal, but I'm pretty sure there is not supposed to be any breaks in the run too, so I'm still not sure what the electrician is thinking I would do when it's time for a second outlet in a different location. Maybe I should just do two outlets now.

actually the guy never came out to do the install, and i never heard back from him so I may be looking for a new electrician anyways

The NEC does not expressly prohibit multiple 240V receptacles on the same branch, so perhaps he was just going to use some acceptable wiring method to parallel them together (but you couldn't really use both at the same time). Alternatively, perhaps he was going to use a feeder / tap system. That is a little more complicated and gets into more exotic areas of the NEC that a residential electrician probably doesn't deal with much. In my case, for my two HPWCs, I put a small, surface mount breaker panel in my garage to both act as the required disconnect means (HPWCs over 60A require a lockable disconnect within line of sight) and to give me a way to break out a single 100A feeder into two 100A branches to the two HPWCs. It was cheap, all things considered, because it saved me from running two 130ft runs of 2awg wire. I just did one 130ft run to that sub panel in the garage and then two 10ft runs from there to each HPWC.

 

[eprosenx]

The NEC does not expressly prohibit multiple 240V receptacles on the same branch, so perhaps he was just going to use some acceptable wiring method to parallel them together (but you couldn't really use both at the same time). Alternatively, perhaps he was going to use a feeder / tap system. That is a little more complicated and gets into more exotic areas of the NEC that a residential electrician probably doesn't deal with much. In my case, for my two HPWCs, I put a small, surface mount breaker panel in my garage to both act as the required disconnect means (HPWCs over 60A require a lockable disconnect within line of sight) and to give me a way to break out a single 100A feeder into two 100A branches to the two HPWCs. It was cheap, all things considered, because it saved me from running two 130ft runs of 2awg wire. I just did one 130ft run to that sub panel in the garage and then two 10ft runs from there to each HPWC.

NEC 625 does phrohibit more than one receptacle on an EV charging circuit.

There is no NEC requirement for the disconnect to be within “line of sight”. You do have to have a locking disconnect if over 60a, but the actual code in article 625 just says it must be “readily accessible”. If you read the definition in article 100 of readily accessible nowhere does it say within line of sight.

Now some AHJ’s could interpret it that way, but I believe that is overreach.

If you do think you will be doing more than one charger in a garage I do agree that a sub panel can be a nice solution for a number of reasons (allows you to use cheaper aluminum wire for the feeder to the panel, provides a disconnect location, provides a place to split power to two hpwc units, provides flexibility for later, etc...)

 

[eprosenx]

Aluminum really won't save a meaningful amount ofoney and will increase heat cycling concerns if you ever do run the circuit at 80amps.

My opinion on why Tesla says no aluminum on the HPWC is the expectation is the circuit will run 80% for hours on end and heat cycle. Aluminum's greater expansion can create issues with this.
A service line rarely if ever runs at 80% of rated and if it does not for long so the common use of aluminum there is less likely to be an issue.

Have you looked at copper prices lately? They are massive!

But yes, copper is overall a superior conductor, however, modern aluminum wire is well accepted and used for nearly all feeder runs to subpanels, for all electrical service entrances, and also for most high amperage branch circuits.

If installed properly (torqued down correctly and with anti oxidant used) I don’t see the issue with using aluminum to a sub panel. Tesla probably banned it going into the hpwc since they did not have enough physical space to land the larger gauge wire required for the aluminum. They also would have needed terminals rated for aluminum Yes, all things being equal I would almost always select copper (unless weight was a limitation).

 

[GWord]

NEC 625 does phrohibit more than one receptacle on an EV charging circuit.

There is no NEC requirement for the disconnect to be within “line of sight”. You do have to have a locking disconnect if over 60a, but the actual code in article 625 just says it must be “readily accessible”. If you read the definition in article 100 of readily accessible nowhere does it say within line of sight.

Now some AHJ’s could interpret it that way, but I believe that is overreach.

I agree that Article 100 provides some examples of what is not Readily Accessible but I think you can glean from section 430 the overall intent of why the disconnecting is needed (i.e. lock out / tag out and safety response), and this is why sight is helpful in these cases. But this is one of many examples where the evolution of the NEC has produced sections that don't seem to jive with one another. In my own designs I have chosen to try to match intent, but I would concede to you that I probably shouldn't have been so aggressive in saying NEC requirement since I made several leaps to get there.

I would debate you on your fist point though. NEC 625.40 / 625.44 does not apply to the Tesla UMC as being discussed here, even the 2017 version which is now more restrictive. The UMC is not fastened in place and, as such, is defined as portable equipment which is allowed to be attached to the premises wiring.

 

[eprosenx]

I agree that Article 100 provides some examples of what is not Readily Accessible but I think you can glean from section 430 the overall intent of why the disconnecting is needed (i.e. lock out / tag out and safety response), and this is why sight is helpful in these cases. But this is one of many examples where the evolution of the NEC has produced sections that don't seem to jive with one another. In my own designs I have chosen to try to match intent, but I would concede to you that I probably shouldn't have been so aggressive in saying NEC requirement since I made several leaps to get there.

I would debate you on your fist point though. NEC 625.40 / 625.44 does not apply to the Tesla UMC as being discussed here, even the 2017 version which is now more restrictive. The UMC is not fastened in place and, as such, is defined as portable equipment which is allowed to be attached to the premises wiring.

Yeah, the disconnect requirements for EVSE's are still quite fuzzy to me. "Readily Accessible" is poorly defined.

I would call out that I think section 430 is very much not-applicable since it is all about motors (but yeah, lots of disconnect requirements there).

My personal feeling is that putting disconnects right next to EVSE's is un-necessary. It is ugly and adds cost and I don't think it adds much safety value. So disconnects make a ton of sense next to AC units since they are serviced all the time, often by tech's that don't have access to the inside of the house. They also have moving parts which can injure you. EVSE's on the other hand are pretty much maintenance free devices. More or less the only part that might be replaceable would be the contactor. I get the requirement to have the ability to "lock off" the breaker at the panel - that makes sense, but having a disconnect lever right next to the EVSE seems silly to me.

On the 625.40 piece, I personally think it is pretty clear:

There are no qualifiers to this and it is not under the subsection about "stationary, portable, or fixed" equipment. It just straight up says you can only have one outlet per branch circuit if that outlet is intended to be used for EV's (i.e. like plugging in the UMC).

 

[eprosenx]

Aluminum really won't save a meaningful amount ofoney and will increase heat cycling concerns if you ever do run the circuit at 80amps.

My opinion on why Tesla says no aluminum on the HPWC is the expectation is the circuit will run 80% for hours on end and heat cycle. Aluminum's greater expansion can create issues with this.
A service line rarely if ever runs at 80% of rated and if it does not for long so the common use of aluminum there is less likely to be an issue.

I was curious so I actually went looking at the costs:

$1.67 a foot
1-1-1 Aluminum SER Cable w/ 3AWG Ground

$5.38 a foot
3-3-3-5 Copper SER Service Entrance Cable

Both rated to 100a at 75c.

3.22 x multiple in cost.

Now yeah, I prefer copper in most cases and I might just pay it myself, but I did want to call out how big the difference is currently.

(note that if you are doing this in conduit and such, aluminum is bigger, so it may be more expensive on that end for larger conduit - though folks also say aluminum is easier to work with than copper even though it is bigger since it is more flexible)

 

[GWord]

On the 625.40 piece, I personally think it is pretty clear:

View attachment 330081
There are no qualifiers to this and it is not under the subsection about "stationary, portable, or fixed" equipment. It just straight up says you can only have one outlet per branch circuit if that outlet is intended to be used for EV's (i.e. like plugging in the UMC).

Isn't it crazy that we can have this much debate about a "standard"? This has always been my biggest beef with the NEC. New areas keep getting bolted on and it is so unwieldy. It's almost like debating the meaning of a passage in the Bible or Koran or something, lol.

I think you will find that taking this compartmentalized interpretation of 625.40, then all 120V connections are disallowed as well (assuming a standard dual receptacle outlets found in most garages). 625.44 gives you the exception list that covers the use of premises wiring. So I think you have found sloppy writing / organization on behalf of the NEC authors but the intent seems to be that premises wiring is not prohibited for use in charging an electric vehicle.

 

[eprosenx]

Isn't it crazy that we can have this much debate about a "standard"? This has always been my biggest beef with the NEC. New areas keep getting bolted on and it is so unwieldy. It's almost like debating the meaning of a passage in the Bible or Koran or something, lol.

I think you will find that taking this compartmentalized interpretation of 625.40, then all 120V connections are disallowed as well (assuming a standard dual receptacle outlets found in most garages). 625.44 gives you the exception list that covers the use of premises wiring. So I think you have found sloppy writing / organization on behalf of the NEC authors but the intent seems to be that premises wiring is not prohibited for use in charging an electric vehicle.

Yeah, I totally agree the NEC certainly could be clearer. Though it does have to handle a bajillion different use-cases so I suspect they are doing the best they can. Though with that being said, there are a lot of areas where a "clean slate" would make a lot of sense (but the havoc in retraining would be huge). There is a LOT of history in the NEC with it having been modified over time.

I actually do believe the NEC is very clear that they don't want you charging off 120v duplex receptacles. I believe if you are intending to charge a car at home they want you to have a dedicated circuit with only a SINGLE receptacle on it.

While I think nearly all of us have plugged in to some random circuit in a pinch to gain a little bit of range, this is not how the NEC wants it done. They want a dedicated circuit for ANY EV charging (and I think it is very much justified given how much power EV's draw and for how long a period of time they draw it).

I actually am particularly annoyed that NEC calls out specific outlet types that you are allowed to use. It seems oddly prescriptive and inflexible...

 

[rhumbliner]

When it comes to copper or aluminum we seem to have waded into personal preferences.

When I installed a 100-amp subpanel in my garage I had to make a 90 ft run from the meter to the garage. Copper would have cost $1.02/ft (XHHW Copper Wire | Wire & Cable Your Way) and aluminum would have cost $0.52/ft (XHHW-2 Aluminum Wire | Wire & Cable Your Way). With the cost saving I opted for extra headroom and used 1/0 awg aluminum at $0.59/ft. Of course I had to bump up my conduit from 1” to 1¼” but my local electrical supply let me have it for the same price.

If you’re doing the work yourself, aluminum is much easier to work with.

 

[Rocky_H]

I think you will find that taking this compartmentalized interpretation of 625.40, then all 120V connections are disallowed as well (assuming a standard dual receptacle outlets found in most garages).

You're still not applying the wording in that section, though.
"Each outlet installed for the purpose of charging electric vehicles [...]"
The NEC code check is for an outlet you are installing. It's not talking about whether you are plugging into existing outlets that you already had in the building for other purposes. You're still allowed to plug things into existing 10-30 outlets, even though the code forbids creating any new ones.

 

[GWord]

You're still not applying the wording in that section, though.
"Each outlet installed for the purpose of charging electric vehicles [...]"
The NEC code check is for an outlet you are installing. It's not talking about whether you are plugging into existing outlets that you already had in the building for other purposes. You're still allowed to plug things into existing 10-30 outlets, even though the code forbids creating any new ones.

The code doesn't forbid the use of premises wiring and receptacles for portable EVSE connection. In fact, the code expressly allows it in 625.44 Eprosenx and I already covered this; this section you refer to is referring to equipment fastened in place, which is why 625.44 makes the distinction. The new, contemplated outlet is servicing a receptacle, not an EVSE. Section 625 doesn't apply in that case since we have no fastened in place EVSE equipment. Again, I'm not saying parallel 14-50s is good design practice in this use case, but it can be made to work with existing code as long as the UMC is just another of many portable appliances that can potentially be plugged in there.​

 

[Glamisduner]

Ok, so two 6awg THHN 100 foot runs runs are fine for two HPWC's to charge two model 3's at 48 amps?
Even if one run is not continuous, so long as it has a only one outlet?

 

[eprosenx]

The code doesn't forbid the use of premises wiring and receptacles for portable EVSE connection. In fact, the code expressly allows it in 625.44 Eprosenx and I already covered this; this section you refer to is referring to equipment fastened in place, which is why 625.44 makes the distinction. The new, contemplated outlet is servicing a receptacle, not an EVSE. Section 625 doesn't apply in that case since we have no fastened in place EVSE equipment. Again, I'm not saying parallel 14-50s is good design practice in this use case, but it can be made to work with existing code as long as the UMC is just another of many portable appliances that can potentially be plugged in there.​

Section 625 absolutely without question applies since the new contemplated outlet IS for an EVSE. It is a portable EVSE (a UMC). So 625.40 applies (only one outlet on a branch circuit), plus 625.44 (A) applies (Portable Equipment).

 

[eprosenx]

Ok, so two 6awg THHN 100 foot runs runs are fine for two HPWC's to charge two model 3's at 48 amps?
Even if one run is not continuous, so long as it has a only one outlet?

Yes, two THHN runs are fine for two HPWC's to charge at 48amps (60a breaker) assuming you don't run the four current carrying conductors in the same conduit (then you get into deration issues - it probably would still be ok, but the math would need to be done).

This also assumes your electrical service has 120a (96a continuous) of available capacity (you could mitigate this requirement if you wired the HPWC's together so they load shared).

It does not matter that the runs are not "continuous". It is fine to have connectors in the middle of the spans as long as they are properly rated connectors for the conductor types you are attaching. Also, the conductors and wire types used in all spans must have sufficient ampacity for the branch circuit in question (i.e. some wire could be NM and other might be THHN for instance).

Oh, also, if we are talking two HPWC's (Wall Connectors) and NOT receptacles you don't need two separate runs of wire. You ARE allowed to split the wire to feed two HPWC's that are communicating HPWC's and that load share. Does that make sense? You just can't have two EV charging 14-50's on one circuit.

 

[Glamisduner]

Yes, two THHN runs are fine for two HPWC's to charge at 48amps (60a breaker) assuming you don't run the four current carrying conductors in the same conduit (then you get into deration issues - it probably would still be ok, but the math would need to be done).

This also assumes your electrical service has 120a (96a continuous) of available capacity (you could mitigate this requirement if you wired the HPWC's together so they load shared).

It does not matter that the runs are not "continuous". It is fine to have connectors in the middle of the spans as long as they are properly rated connectors for the conductor types you are attaching. Also, the conductors and wire types used in all spans must have sufficient ampacity for the branch circuit in question (i.e. some wire could be NM and other might be THHN for instance).

Oh, also, if we are talking two HPWC's (Wall Connectors) and NOT receptacles you don't need two separate runs of wire. You ARE allowed to split the wire to feed two HPWC's that are communicating HPWC's and that load share. Does that make sense? You just can't have two EV charging 14-50's on one circuit.

Right now I'm going for one 14-50, but wanted to be sure I can upgrade either to a HPWC and / or another 14-50 later if the wife decides to also buy an EV.

 

[Tezlanian]

My box is in my tuck under garage right next to my car's charge port. Cost me diddly.

 

[GWord]

Section 625 absolutely without question applies since the new contemplated outlet IS for an EVSE. It is a portable EVSE (a UMC). So 625.40 applies (only one outlet on a branch circuit), plus 625.44 (A) applies (Portable Equipment).

So then to take this to its logical conclusion, we have now deduced that all new 14-50 installations must fall under 625.40 since there's the chance that sometime, in the service life of the receptacle, someone could plug in a portable EVSE. We can no longer contemplate a receptacle, we must design for every device that could ever be plugged in. At any rate, we seem to have gotten to the point where multiple engineers argue ambiguous code for sport. This is usually the time at the office where we all have to get back to work.

 

[eprosenx]

So then to take this to its logical conclusion, we have now deduced that all new 14-50 installations must fall under 625.40 since there's the chance that sometime, in the service life of the receptacle, someone could plug in a portable EVSE. We can no longer contemplate a receptacle, we must design for every device that could ever be plugged in. At any rate, we seem to have gotten to the point where multiple engineers argue ambiguous code for sport. This is usually the time at the office where we all have to get back to work.

Yeah, while I do agree that it is somewhat annoying that different rules are applied depending on what a receptacle is going to be used for, but none the less, that is my reading of the NEC. If you define that 14-50 will be used for a Range, then the rules pertaining to ranges apply (your load calc's are based off the range nameplate, etc...). Then if you define the 14-50 is going to be for an RV a separate set of rules apply (though to be honest, I have not found a section on RV plugs in the code yet other than for official RV parks). But if it is for an EV, it is pretty clear to me that section 625 applies. I don't know why you would have all these rules in 625 unless they absolutely intended it to apply to receptacles installed for EVSE's.

At the end of the day, I guess there are two goals:

1. Don't burn the house down.
2. Get the inspector to sign off on it.

From what we have seen on the forums, the level of knowledge of inspectors about EV's is very across-the-board and generally poor in most areas. Many don't seem to know anything about section 625.

So to really respond to your comment above, I do not think that all 14-50's need to comply with 625, just ones that are intended for EV charging. Most of us could just lie and say the 14-50 was for an RV and yeah, 625 would not apply then.