Model S - HPWC (High Power Wall Connector)

[Electrical_Eng]

You can fit #2 into the terminals carefully, but it's tight - you have to make sure you get all the strands in there. I believe Tesla's installation specifies CU-only. If you use AL, they recommend taking it to a disconnect or junction box just before the HPWC and using proper connectors with the final length of copper.

Thank you to all who responded on the Copper vs. Aluminum. The licensed electrician is running copper to the wall charger. Tesla's installation does not mention aluminum so I will go with copper to be safe. I don't want to have to worry about aluminum wiring developing into loose connections with the wall charger.

Thanks again.

 

[FlasherZ]

I added a question to the FAQ of whether the HPWC can be plug-and-cord connected at the 50A setting, following a reply from Tesla.

Spoiler: NEC and Tesla's instructions as published currently permit this, confirmed by several AHJ's. However, Tesla is concerned about the practice and may amend the installation instructions to require permanent wiring methods, which would be required per NEC 110.3.

See here for the FAQ:
FAQ: Home Tesla charging infrastructure QA

 

[m6bigdog]

...


#2 is only good if it's wire-in-conduit and not NM cable. #2 NM cable is good to only 95A, and therefore does not work for an HPWC set at 80A. NEC 310.19 and 334.

FWIW, I assume we have a difference of interpretation.
So you are saying the EVSE device ampacity (continuous load) and overcurrent protection device (OCPD) rating are the same things.

That is where we differ:
The HPWC is an 80 amp continuous rated EVSE device and the Tesla chargers can only draw 80 amps continuous, 20kW. The HPWC maximum branch circuit OCPD is 100 amps as it needs to be 125% of the continuous load. The ampacity specification for the HPWC is 80 amps continuous not 100 amps, as the 100 amp circuit breaker is the OCPD not a current limiting device for the EVSE load.

Ampacity is defined as: NEC Article 100 Definitions: "Ampacity. The maximum current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating".

#2 AWG NM-B which has an ampacity rating of 95 amp and IMHO, sufficient for the HPWC "continuous - conditions of use" which is 80 amps maximum!!!
Therefore #2 AWG NM-B will never carry any thing close to 95 amps continuous with the HPWC set at 80 amps charging the Tesla. Also, a circuit with 100 amp breaker cannot have an ampacity of 95 amps continuous because that exceeds the 125% OCPD requirement, without even thinking about the wire size.

There are some places where the NEC dictates maximum circuit breaker size for the branch circuit wire size, however that I am aware this is not one of them.

Overcurent protection requirement:
"625.40 Overcurrent Protection. Overcurrent protection for feeders and branch circuits supplying electric vehicle supply equipment shall be sized for continuous duty and shall have a rating of not less than 125 percent of the maximum load of the electric vehicle supply equipment. Where noncontinuous loads are supplied from the same feeder or branch circuit, the overcurrent device shall have a rating of not less than the sum of the noncontinuous loads plus 125 percent of the continuous loads."

 

[FlasherZ]

(EDIT: Note that in the original quote I mentioned 310.19 - the proper section is 210.19.)

Don't worry, this is frequently misunderstood, but the good news is that the NEC is crystal clear about the matter. I've also consulted with the chief code compliance officers and inspectors that I work with on a regular basis, and they've been unanimous. In addition, I posed the question on Mike Holt's forum, which deals with the specifics of code compliance, and received a unanimous agreement.

To your query, absolutely not -- conductor ampacity and OCPD are two different things. While you addressed sizing of the OCPD, you failed to size the conductor per 210.19.

So let's start out with how we get there:

• Article 625 states that vehicle charging loads are always to be considered continuous loads.
• Section 210.19(A)(1)(a) says that "Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch circuit conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load." An HPWC configured for an 80A continuous load, then, requires a conductor with an "allowable ampacity not less than" 100A.
• Section 334.80 requires you to use the 60 degree column of 310.15(B)(16) when determining allowable ampacity of the NM cable.
• Allowable ampacity of conductors is defined in 310.15. The 60 degC column of 310.15(B)(16) states that the ampacity of #2 copper conductors is 95 amps.
• 95 amps is not "not less than" 100 amps, and so #2 NM would not be usable for this application.
• The 240.4 "next size up" rule, for breakers only, doesn't apply to conductors.

Of course, just like in anything related to the NEC, the only person whose opinion matters is the electrical inspector (or his supervisor, if you escalate) or the insurance company investigator, depending on what event triggers the inspection. I sincerely doubt there'd be a safety issue with #2 NM, but it is an illegal install and may come with insurance and/or liability implications. Three of the local inspectors I deal with said they would fail a #2 NM install to an HPWC.

 

[Electrical_Eng]

(EDIT: Note that in the original quote I mentioned 310.19 - the proper section is 210.19.)

Don't worry, this is frequently misunderstood, but the good news is that the NEC is crystal clear about the matter. I've also consulted with the chief code compliance officers and inspectors that I work with on a regular basis, and they've been unanimous. In addition, I posed the question on Mike Holt's forum, which deals with the specifics of code compliance, and received a unanimous agreement.

To your query, absolutely not -- conductor ampacity and OCPD are two different things. While you addressed sizing of the OCPD, you failed to size the conductor per 210.19.

So let's start out with how we get there:

• Article 625 states that vehicle charging loads are always to be considered continuous loads.
• Section 210.19(A)(1)(a) says that "Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch circuit conductor size shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load." An HPWC configured for an 80A continuous load, then, requires a conductor with an "allowable ampacity not less than" 100A.
• Section 334.80 requires you to use the 60 degree column of 310.15(B)(16) when determining allowable ampacity of the NM cable.
• Allowable ampacity of conductors is defined in 310.15. The 60 degC column of 310.15(B)(16) states that the ampacity of #2 copper conductors is 95 amps.
• 95 amps is not "not less than" 100 amps, and so #2 NM would not be usable for this application.
• The 240.4 "next size up" rule, for breakers only, doesn't apply to conductors.

Of course, just like in anything related to the NEC, the only person whose opinion matters is the electrical inspector (or his supervisor, if you escalate) or the insurance company investigator, depending on what event triggers the inspection. I sincerely doubt there'd be a safety issue with #2 NM, but it is an illegal install and may come with insurance and/or liability implications. Three of the local inspectors I deal with said they would fail a #2 NM install to an HPWC.

Mike Holt is an awesome guy. I met him over 20 years ago and he helped me out a lot. He even has (or had) an 800 phone number you can call to ask him code questions directly! He refused to take any compensation for helping me out. I hope to go to one of his seminars in the near future.

 

[FlasherZ]

Mike Holt is an awesome guy. I met him over 20 years ago and he helped me out a lot. He even has (or had) an 800 phone number you can call to ask him code questions directly! He refused to take any compensation for helping me out. I hope to go to one of his seminars in the near future.

Yes he is. He's also got great videos on YouTube that explain a lot of nuances about why portions of the code are the way they are. Grounding & bonding is probably one of the most understood areas, mostly because a lot of people don't understand how electricity flows and what happens in various failure situations - his videos help explain a lot of it.

 

[AWDtsla]

I believe this is a Canada-specific rule. US NEC has different wording (which could be different at a state or local level) which says you must have disconnect means, but a breaker with a permanently attached lockout counts as disconnect means which is what I have on mine.

Anyone have a picture of what this permanent lockout looks like? Trying to avoid another ugly box in the garage.

 

[pgiralt]

Anyone have a picture of what this permanent lockout looks like? Trying to avoid another ugly box in the garage.

This is similar to the one I have on my breaker:

Type-CH Circuit Breaker Padlocking Device-CHPLCS - The Home Depot

Seems like "semi-permanent" is good enough. I'm sure FlasherZ might have something additional to say about exactly what the code says about something like this.

 

[FlasherZ]

This is similar to the one I have on my breaker:

Type-CH Circuit Breaker Padlocking Device-CHPLCS - The Home Depot

Seems like "semi-permanent" is good enough. I'm sure FlasherZ might have something additional to say about exactly what the code says about something like this.

There are differences here between NEC 2011 and 2014. NEC 2014 centralized and standardized the various sections that were requiring "lockable disconnecting means".

NEC 2014: 625.42 says that disconnecting means shall be provided and installed in a readily accessible location, and shall be lockable open in accordance with 110.25. 110.25 says that the "provisions for locking shall remain in place with or without the lock installed", meaning that the temporary lock-out brackets that don't stay in place without the lock installed will not work. What pgiralt refers to stays in place whether or not the lock is installed, and is sufficient.

As for "readily accessible", this is dependent upon the inspector's interpretation. Some inspectors will interpret that to mean within the same room, within eyesight. Others will interpret it to mean it simply needs to be accessible to the operator - meaning in a home, a lockout on the breaker is sufficient.

 

[David J]

I am installing an HPWC with 50 amp service. I have run two copper 6 gauge hot wires and a ground (romex) from my circuit breaker box to the wall unit, about 60 feet total. I want to also install a 14-50 outlet next to the HPWC in case it fails/requires service. I will put a simple connector box in between them in which I will splice the wires (3 hot, 3 hot, 3 ground). Both will never be used at the same time since they will both share the same feeder wires and 50 amp breaker. All exposed portions will be in conduit. Question: since the 14-50 outlet is made for 2 hot, a ground, and a neutral, is it okay to install it without the neutral? I'm told it will be okay as long as I only use it to charge the car. In any case, why does the 14-50 use 4 wires and the HPWC only 3? Finally, would my set-up pass code? I live in Florida.

 

[hcsharp]

I am installing an HPWC with 50 amp service. I have run two copper 6 gauge hot wires and a ground (romex) from my circuit breaker box to the wall unit, about 60 feet total. I want to also install a 14-50 outlet next to the HPWC in case it fails/requires service. I will put a simple connector box in between them in which I will splice the wires (3 hot, 3 hot, 3 ground). Both will never be used at the same time since they will both share the same feeder wires and 50 amp breaker. All exposed portions will be in conduit. Question: since the 14-50 outlet is made for 2 hot, a ground, and a neutral, is it okay to install it without the neutral? I'm told it will be okay as long as I only use it to charge the car. In any case, why does the 14-50 use 4 wires and the HPWC only 3? Finally, would my set-up pass code? I live in Florida.

Would not pass code and not really safe long-term. Will you always be standing in your garage from now until eternity to enforce the don't-use-both-at-once rule? Of course not, and some day somebody will do something wrong. Also if someone uses the 14-50 for a purpose that it's made for (such as an appliance or RV) you will have a dangerous situation because the ground wire may end up being used as a neutral conducting wire. That will put enough voltage on parts of your appliance or RV that are normally grounded to hurt somebody. The 14-50 has a separate Neutral for a reason: it carries up to 50A of current. I doubt your gnd wire is sized for that. It's a 120 as well as 240v outlet. It's worth it to run separate wires from the breaker to the NEMA 14-50 outlet.

 

[David J]

Thanks for the quick response. My wife and I are the only two people who live in the house. I have only used a 240V outlet probably twice in my life - both times for moving day into a new house, to plug in a dryer. This outlet will be in the far corner of a 3 car garage - away from everything. When I move out one day, I will take the HPWC with me and just disconnect the 14-50 outlet. I would probably even take out the 50 amp breaker any my wire. I could also label the outlet, "for Tesla charging only - no neutral", in case I drop dead one day. So I appreciate your safety concerns, but while typing this I am wondering if the 14-50 outlet will even work to charge the Tesla, with only 3 wires? The Lowe's electrician says yes but does he know what he's talking about? Thanks again for helping me.

 

[pgiralt]

As @hcsharp mentioned, there is no way this would pass an inspection. Why not just run larger conduit and put two runs of cable through it - one for the HPWC and one for the 14-50 (with a neutral). If you have the space for it, install the two breakers as well and then you'll never have to worry about it.

I would definitely never install a permanent 14-50 outlet without a neutral. Yes, it will work to charge your Tesla, but it's unsafe for devices that need the neutral there.

 

[David J]

Ok guys, thanks so much for your help.

 

[FlasherZ]

My private response:

Technically, it's a violation to install a 14-50 outlet without a neutral. If someone were to try to use it for other appliances or an RV, it could destroy the appliances.

The 14-50 requires 4 wires because it is a 120/240V receptacle, while the HPWC is a 240V-only appliance and doesn't require neutral. NEMA 14 is used in applications where 240V and 120V are used. It will not likely pass an inspection.

I've seen a few solutions -- the best and easiest is to pull a neutral with the circuit to connect to the 14-50. But others have filled the neutral blade in the receptacle with epoxy and cut off the neutral prong on the UMC adapter. That way it will work in all NEMA 14 outlets but prevent an RV or other appliance from being plugged in.

(I don't really like the latter one at all but it's an option. It probably wouldn't pass inspection, though.)

 

[miimura]

If you really want to do this, pull a neutral wire from the panel with the other wires for the 14-50. You can also use a transfer switch to make sure that only one is active at the same time. That should pass code.

[Edit] Also known as a double pole safety switch.
Siemens General Duty 60-Amp 240-Volt Double-Pole Outdoor Non-Fusible Safety Switch-LNF222RU - The Home Depot

 

[Rocky_H]

If you really want to do this, pull a neutral wire from the panel with the other wires for the 14-50. You can also use a transfer switch to make sure that only one is active at the same time. That should pass code.

[Edit] Also known as a double pole safety switch.
Siemens General Duty 60-Amp 240-Volt Double-Pole Outdoor Non-Fusible Safety Switch-LNF222RU - The Home Depot

This seems like the easiest way to have a fully code compliant install, with a toggle switch inline.

 

[hcsharp]

This seems like the easiest way to have a fully code compliant install, with a toggle switch inline.

I doubt if it's easier than running separate supply wires to the 14-50. You might as well do it right. It's not that hard.

 

[Rocky_H]

I doubt if it's easier than running separate supply wires to the 14-50. You might as well do it right. It's not that hard.

It may not be hard; it might be impossible. :smile: Running it separately assumes you have room and capacity in your electrical service to fit in two 50A breakers to have them both wired in at the same time. Since David J’s original question was referencing one breaker, I figured we’re talking about a situation that can’t fit in having them both wired, so that’s the assumption I was going with. A switch box is a way to do it with one breaker.

 

[pilotSteve]

I've had my HPWC since 12/2012, ordered with my Sig. It was an early unit that had the fuses updated (that was two years ago) and Tesla kindly send a technician to my house to replace them and update the HPWC. Perfect 80A operation since then until a month ago, then the car started refusing occasionally to initiate charge. Cable plugged in but would not locked and no green ring. Portable connector always worked, just the HPWC that was flakey.

Finally HPWC became seriously unreliable. Called Tesla and the check my logs remotely. Yes they could see the pilot signal was not working correctly on my HPWC. So they ordered a new cable and this morning (Saturday) the technician drove to my house and replaced the cable. All working perfectly.

Some thoughts:
(1) its great that Tesla extended the HPWC warranty to match the car since they were purchased on the same invoices. So I have 8 years, unlimited miles.
(2) Tesla techs are some of the most awesome and service-oriented people I've met. Carl really knows his stuff and is the kind of person I'd gladly have come to my house.

Loving the car and the company since 2012! (Well actually I placed my Sig reservation in June 2011).