Tesla or 14-50

[tliving]

I just put a NEMA 14-50 in. I bought a second UMC. Originally that was a cheaper approach and you don't need a HWPC for charging at home. But there's still a reason for the 2 UMC approach: if you plan on long road trips where you could be far from Tesla service then taking both your UMC's provides redundant charging options. With a HPWC and a UMC you can only take one on a trip.

 

[thecloud]

I just put a NEMA 14-50 in. I bought a second UMC. Originally that was a cheaper approach and you don't need a HWPC for charging at home. But there's still a reason for the 2 UMC approach: if you plan on long road trips where you could be far from Tesla service then taking both your UMC's provides redundant charging options. With a HPWC and a UMC you can only take one on a trip.

Not sure what you're saying here. You can't use both UMCs at the same time, obviously. If one UMC fails, then you have a backup? Is that really likely to happen?

I went with a NEMA 14-50 outlet instead of a HPWC in my garage as well.
1) My panel is 100 amps max and cannot really deliver more than 40 amps to a single circuit. "Ask your electrician if HPWC is right for you."
2) Last year, the HPWC cost much more than a spare UMC.
3) If/when I go to sell my house, a 14-50 outlet is more generally useful to potential buyers than a hard-wired HPWC, which is only useful to Tesla owners.

 

[m6bigdog]

Does your UMC bear a listing mark? The UL database only shows the HPWC (FFWA.E351001) and the J1772 adapter (FFVI2.E353200). Mine isn't listed, which makes me assume that Tesla calls it part of the car.

UL 2594 (standard under which the HPWC is listed) permits cord-and-plug connected sets. Because the HPWC is shipped with terminal blocks and not a power cord, the HPWC listing doesn't include the power supply conductors and therefore is not violated when cord-and-plug is connected to it. As long as article 625 is satisfied (12 in. maximum cord length) along with all other wiring methods (proper cable clamps, etc.), then you can use the HPWC with a cord and plug set (bonus is that it qualifies as a disconnect if you can lock it ).

It's going to be pretty tough with a cord that big to satisfy the 12" maximum length on the cable.

I have not found any instruction which requires it to be hard-wired, which would trigger the 110.3 manufacturer's instruction clause.

Nope the UMC does not have a listing Mark.
I was surprised the plug adapters for the UMC are not listed.
Only the J1772 adapter is CE and UL component (UR) listing. I anticipate because the J1772 adapter and charge stations are electrical infrastructure and independent of any vehicle manufacture.

As for cord and plugging the HPWC, we have a difference of interpretation.
FWIW, Typically the UL Listing FFWA.E351001, UL2594 Standard and the NEC 110.3(B) requires the qualified installer to follow the EVSE manufacture installation instructions.
This is all about how the equipment was investigated and tested for the UL listing (110.2 Approval) the 1st requirement for installation by the NEC, it must be listed and just because it is a cord and plug EVSE does not dissolve the Listing requirement.

That I can see, Tesla only includes the hard wiring method in the instructions and does not provide provision for installing the HPWC with a cord and plug, hence the NEC and UL listing does not include that installation method for the Tesla HPWC.
Also, even though NEC 625 may allow for cord and plug EVSE it is still is up to the building official (AHJ) to allow/approve that installation, especially if the EVSE does not come with a cord and plug attached or a cord and plug are not part of the EVSE installation instructions.
Also, also, the current HPWC installation instruction (page 2 Warnings) do require "grounding through a permanent wiring system or an equipment grounding conductor" and cord and plug installation does meet the permanent grounding requirement for the HPWC.

Is cord and plug safe? That is a question for the EVSE manufacture and UL.
The #1 question, could the chargers/battery pack back-feed the plug when it is disconnected from the receptacle?

IMHO, hard wiring the HPWC is the best wiring method (most reliable over the long term) especially for high amperage fixed in place equipment.

As for daily charging using the UMC, irrespective of the attached adapter, repetitive plug insertion into a receptacle will degrade the contacts over time and this is why the UMC is other than the best method; as sooner or later the receptacle/plug contacts will fail and the max current usage for the plug type will have little tolerance for a weaken contact.

Should you move and the new occupant has no need for the HPWC it can be easily removed and a receptacle installed in its place or the breaker switched off and the wires terminated with wire nuts in a junction box.

 

[ROCDOC]

I had a 14-50 and was happy with it until I got a HPWC (after the price drop) with 80 amps. Now if I forget to plug in the car at night, I can do so in the morning and the charging speed allows me to top off while I get ready for work. The other reason for the HPWC is the length of the cable - 25 feet I believe, which allows me to pull in head first in my garage without straining the cable of the UMC to fit.

 

[FlasherZ]

As for cord and plugging the HPWC, we have a difference of interpretation.
FWIW, Typically the UL Listing FFWA.E351001, UL2594 Standard and the NEC 110.3(B) requires the qualified installer to follow the EVSE manufacture installation instructions.
This is all about how the equipment was investigated and tested for the UL listing (110.2 Approval) the 1st requirement for installation by the NEC, it must be listed and just because it is a cord and plug EVSE does not dissolve the Listing requirement.

That I can see, Tesla only includes the hard wiring method in the instructions and does not provide provision for installing the HPWC with a cord and plug, hence the NEC and UL listing does not include that installation method for the Tesla HPWC.
Also, even though NEC 625 may allow for cord and plug EVSE it is still is up to the building official (AHJ) to allow/approve that installation, especially if the EVSE does not come with a cord and plug attached or a cord and plug are not part of the EVSE installation instructions.
Also, also, the current HPWC installation instruction (page 2 Warnings) do require "grounding through a permanent wiring system or an equipment grounding conductor" and cord and plug installation does meet the permanent grounding requirement for the HPWC.

Your interpretation is not unsafe, so if that's what you choose to interpret, then that's certainly ok. And you're right, the only opinion that matters is the AHJ who inspects it and/or the fire marshal & insurance investigators, depending upon when it's being inspected. My opinion is that - just an opinion, formed from my reading, discussions with AHJ's and other electricians, and personal experience.

A few things about the "manufacturer's instructions" provision (110.3) in the code: they deal with EXPLICIT instructions, not implicit. If you can point me to the wording in the installers' manual that says hardwiring is *required* or that cord-and-plug is *prohibited*, then you have a point; if it's just implied because of typical installation, then it's not a manufacturer instruction - and you fall back on any other NEC provisions.

For example, let's look at stove tops and wall ovens. Many homes have a single 40-amp circuit that can supply both a cooktop and wall oven at the same time. Many times, the installation instructions for the equipment will "suggest" a 40-amp circuit for the cooktop and a 20-amp circuit for the oven, especially if they were sold as two separate units (the manufacturer's can't possibly consider all the different ways it could be installed). The NEC permits them to be connected to the same circuit (with appropriate demand factor applied), and I've never seen an AHJ fail to approve such an installation - and they're not rare.

Finally, you quote "grounding through a permanent wiring system or an equipment grounding conductor" as a way of saying that hardwiring is required, but that's not true. An EGC doesn't stop being an EGC just because it is put through a cord, plug, and receptacle. The EGC in the UMC, provided by the adapter, is still an EGC.

The #1 question, could the chargers/battery pack back-feed the plug when it is disconnected from the receptacle?

What does this have to do with cord-and-plug connecting the HPWC? The answer is obviously no, as the car and equipment isn't capable of doing V2G at this point.

IMHO, hard wiring the HPWC is the best wiring method (most reliable over the long term) especially for high amperage fixed in place equipment.

No doubt, but your opinion doesn't mean cord-and-plug connecting the HPWC is prohibited.

Just to ensure I wasn't off my mark, I checked with two different municipal inspectors near me (who I work with on a regular basis) and they said they had no concerns with cord-and-plug connecting the device, as long as there were no explicit instructions by the manufacturer that said it should not be.

 

[m6bigdog]

Your interpretation is not unsafe, .....

Finally, you quote "grounding through a permanent wiring system or an equipment grounding conductor" as a way of saying that hardwiring is required, but that's not true. An EGC doesn't stop being an EGC just because it is put through a cord, plug, and receptacle. The EGC in the UMC, provided by the adapter, is still an EGC.

Just to ensure I wasn't off my mark, I checked with two different municipal inspectors near me (who I work with on a regular basis) and they said they had no concerns with cord-and-plug connecting the device, as long as there were no explicit instructions by the manufacturer that said it should not be.

Yep and that is why it is a listing and code interpretation.

My AHJ experience dealt with overall/final responsibility for interpreting the component and device listing/approvals for industrial/R&D usage and NEC installation methods and that is where most interoperations go beyond the explicit listing/approval.
As the testing lab and listing is very explicit, that is, if it is not described in the manufacture installation instruction or listing then it has not been tested or approved for that use or installation method. Therefore, equipment listed for residential usage cannot be implied as approved for commercial use just because it is not explicitly disallowed.

The best approach to resolve the cord and plug issue it to ask for an interoperation form UL or Tesla and not anticipate a NEC knowledgeable individual knows explicitly what the HPWC installation requires are beyond what is included in their instructions and the listing.

However, the HPWC explicitly requires "grounding through a permanent wiring system" and there is nothing permanent about grounding through a cord and plug regardless of where the ground is derived, EGC or grounding conductor, i.e., as a receptacle is permanently grounded but the cord and plug connected equipment is not. Therefore, the HPWC could be connected to the vehicle charge port but not grounded through the unplugged wall receptacle.

Also the cord and plug usage with the UMC has nothing to do with the fixed in place installation requirements of the HPWC as they are completely different devices (design) with the same function and only the HPWC is listed.

 

[FlasherZ]

However, the HPWC explicitly requires "grounding through a permanent wiring system" and there is nothing permanent about grounding through a cord and plug regardless of where the ground is derived, EGC or grounding conductor, i.e., as a receptacle is permanently grounded but the cord and plug connected equipment is not. Therefore, the HPWC could be connected to the vehicle charge port but not grounded through the unplugged wall receptacle.

It does not.

It says, and I quote:

The High Power Wall Connector must be grounded through a permanent wiring system or an equipment grounding conductor.

(Emphasis mine.)

The grounding prong on a plug, and the corresponding wire it's attached to inside the HPWC, is an equipment grounding conductor. It does NOT require a permanent wiring system. Anyone who tells you otherwise is flat-out wrong, period. The NEC's definition of EGC is "The conductive path installed to connect normally non current carrying metal parts of equipment together and to the system grounded conductor or to the grounding electrode conductor or both", and if the ground prong / wire on an appliance plug were not considered an EGC, then the use of EGC in the Code wouldn't make any sense when it talks about appliances' EGC requirements.

Also the cord and plug usage with the UMC has nothing to do with the fixed in place installation requirements of the HPWC as they are completely different devices (design) with the same function and only the HPWC is listed.

Please provide the reference where Tesla explicitly instructs the HPWC must be permanently-wired. When you can do that, I'll concede you're right. Unfortunately for you, it doesn't exist. The UL 2594 standard (evaulation criteria for type FFWA listing) has no such requirement that EVSE be permanently wired for listing under the category that Tesla uses; in fact, section 12 of the standard specifically allows for cord-connected and direct plug-in devices (I don't have access to the listing standard to quote it right now, but I have seen it). There is no evidence to suggest that Tesla intended to list it only as direct-wire -- e.g., the listing does not specifically note permanently-wired only, nor do the instructions explicitly require it. For 110.3, you need explicit instructions by Tesla, not implicit assumptions based on the fact they provided a terminal block inside the unit. Otherwise, fall back to the requirements in the Code, which permits it.

That said, for most it's a moot point as art 625 requires GF-unprotected cord-and-plug conductors feeding HPWC's to be 12" or less, and a wall connector with a 12" cord and plug and nearby receptacle will likely get in the way of a 50A receptacle. The bottom line, though, is that it is perfectly legal:

In response to your message, I looked over the Tesla instruction document and nothing that I can see there or in the NEC precludes the use of a cord to connect that device to a 50 amp outlet.  It would be a legal install within the city.

Your interpretation goes against hundreds of code-compliant appliance installs on a daily basis - not just EVSE's, but across a wide range of appliance and infrastructure types. There is nothing in Tesla's installation instructions that requires "permanent wiring methods".

(EDIT: changed quote from inspector to "CODE" instead of "QUOTE" to clarify vs. quoted post.)

 

[Electricfan]

Add another vote for two UMCs and a 14-50 outlet in your garage.

I have one in my trunk, and one left plugged into my 14-50 outlet in my garage all the time (except in a lightning storm like we had in Houston last night - you can't unplug a HPWC if you hard wire it!). As others have noted, the damn cord is too short, so I had to put the 14-50 outlet on the side wall of my garage, so I can park nose in. The cord goes across the floor from the left side wall of the garage to the Tesla parked on the right side. I have a couple of wood boards taped to the garage floor so I can run the UMC cable through them. The Volt I park on the left side of the garage rolls over the boards with the cord tucked in between, protecting it from being squashed. I used to drive over it, but decided it probably wouldn't last long doing that.

That said, the wall charger was so expensive in 2013 when I got my first Model S I really didn't consider it. If I had it to do over, I think I'd still go with two UMCs for reasons others have stated - you have a back up to take on a trip, and its just basically more versatile. The wall charger can't help you anywhere but your garage. But it really doesn't make much difference.

By the way, everything fails. Manufacturers call the statistic that describes failure rates as "MTBF" or "mean time between failure". They do not build ANYTHING to last forever. So, having two UMCs is a good idea - when the one you use everyday fails - you have an immediate replacement until you get a new UMC. If you only have one UMC and one HPWC, and your UMC fails, you can't take the HPWC with you if you hard-wired it!

 

[chriSharek]

Electricfan, would you have got another UMC if the HPWC was only $750 last year?