Imagine a new Gen3 wall connector has a fault and draws 100A. What happens? Well, the HPWC is only rated for 60A, if it draws 100A then potentially very bad stuff occurs. Is the breaker going to trip and protect against this happening? No, not if it's still a 100A breaker. The 100A breaker is perfectly happy to have the HPWC overdrawing current. That's why you size the breaker appropriately.
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Gen 3 Wall Connector
- Thread starter SpiceWare
- Start date
Again, if the HPWC draws more than 60amps, up to 100 amps, it won’t matter, the line is build to handle 100amps. House wiring can handle. The HPWC, is fried, that’s why they have a fuse in the HPWC. A 60Amp, breaker won’t protect a 48amp HPWC. The voltage has never changed, is still 240v.
Sure, no big deal if a bit of electrical hardware attached to your wall catches fire in the middle of the night, ends up igniting the wall it's mounted on, and burns your house down while everyone's asleep. You can be content in the knowledge that the in-wall wiring could handle the load. Plus, as extra bonus, you may find out that your insurance carrier rejects your fire damage claim due to the negligent installation of your EVSE. But, whatever. Just another Sunday, no big deal. /sarcasm
Everything downstream of the breaker has to be rated to take the level of current allowed by the breaker. A HPWC which charges at up to 48A is still actually rated for 60A (peak). But EV charging is a continuous load, and continuous loads are limited to 80% of the peak allowable which results in the 48A limit.
Again, I’ll use the NEC to make my point: NEC 210.20: Overcurrent Protection. Branch-circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with 210.20(A) through (D).
To respond to “fear mongering”, anyone with any familiarity of building or electrical code knows those rules are written in blood- something very bad happened to someone in the past to get that rule into the code.
I hope at this point everyone reading this thread realizes MakeUSGreat doesn’t know what he’s talking about. Please don’t listen to him.
Nothing in the documentation of the WC says it can handle above 60A. The testing and listing process (from which the manufacturer install instructions are derived) spec the max breaker. For the Gen 3 WC, this is 60A. There’s nothing in the documentation that says anything above 60A is allowed. If the listing and install instructions allowed for a 100A breaker, MakeUSGreat would be correct, but he’s not, and he’s not even making that argument.
Here’s a thought experiment- what if one of the known failure modes is for a circuit board to go bad, draw a continuous 80A for 2 hours which melts the terminals and starts a fire? Tesla engineers and the listing authority would say, no problem, we spec’d a max OCPD of 60A, so this will never happen. In the case of a 100A breaker upstream of the WC, you’ve got at the minimum a fire and a denied insurance company claim. Hopefully no one gets hurt.
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UL listing (done by Underwriters Laboratories, founded in response to insurance companies needing EEs to investigate FIRES) is a rigorous process that sets the OCPD spec and a range of other install requirements based on temperature rise, failure methods, among other things. This testing establishes limits to ensure safe operating conditions.
Here’s more info on how they track devices involved in incidents after installation. One of the first questions they ask is “was the device installed according to UL listing specifications.”
Market Surveillance
“The following are examples of what should be reported:
Here’s more info on how they track devices involved in incidents after installation. One of the first questions they ask is “was the device installed according to UL listing specifications.”
Market Surveillance
“The following are examples of what should be reported:
- Fire, shock or other personal injury or property damage allegedly caused by UL certified products
- ...
- Noncompliance with UL requirements for that product”
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Hmm, maybe I should build a wall between the HPWC and anything that might burn. Now to just figure out how to make the power company pay for it.
/edit. To everyone else, thanks for the heads up. I'll swap the breakers (or look to swap the Gen 3 units for Gen 2 ones if possible).
MXLRplus
Active Member
The breaker protects the wiring, not the device. This is why so many devices have circuit breakers or fuses built into them.
Who knows what you will use that circuit for in 10 years? Or the next homeowner. The minute you downrate the breaker, nobody is going to know it was robust enough to handle more current.
Who knows what you will use that circuit for in 10 years? Or the next homeowner. The minute you downrate the breaker, nobody is going to know it was robust enough to handle more current.
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It's literally 2 posts on a gravel island in a commercial parking lot, so I'm not too worried about what the future homeowner thinks. The only things being serviced are the HPWC. The power company put in a meter and new service off the transformers you see in the below pic just for the destination chargers. It's probably the only way we easily were able to get 400amp service, as the meter is 8' from the transformer. I wish 277v was formally supported when we put them in, as they could easily have had that as a feed.
One more time: NEC (that stands for National Electrical Code) 210.20: Overcurrent Protection. Branch-circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with 210.20(A) through (D).
Another place where this is relevant is that both the conductor type and the temperature listing on the equipment determine which column on table 310.15(b)16 you use for determining allowable ampacity. In a lot of cases the equipment listing requires you to use a lower temperature column than you would otherwise be allowed to (this is why NM/Romex was/is required to be used at the 60C column, even though the insulation is rated higher- the light fixtures were the limiting factor and fires were the result)
As for future homeowners and derating breakers, wire type and gauge is marked on the jacket and can also be measured.
The spec sheet for the WC calls for external OCPD, and is clearly called out elsewhere in the manual as 60A, as well as in the software during commissioning.
MXLRplus
Active Member
First - I don't agree with any commercial application using the G3 HPWC. The cable is really wimpy. And short. If you have 277, run it. Running 208 or 240 is a waste of materials and electricity. And if you're supposed to put each G3 on its own breaker that just runs up your costs.
I've moved into a number of commercial buildings over the years. I don't trip breakers. It damages the breakers and is hard to troubleshoot. And if the wire, connections, and disconnects are sized and installed properly, I never trip a breaker unless something is destroyed. I don't use the breaker as a limit switch, I use it as a safety device. I'll never run a slo-blo at the panel ever, that's not a replacement for a heavier circuit. Unless I like fires.
You noted AC units. When my AC units blow up, I have to get on the roof. That's where the disconnect and circuit breaker / fuses are at. Why the heck would you run two in-line circuit breakers on the same line at the same amps? To double your troubleshooting time?
I'm primarily 480/277. I have both the G2 and G2 HPWCs here that I'm setting up. 208 blows big ones. Heavier wire, high losses. Harder to balance, breakers cost more. I might test the G3 at 277 for laughs. But the cord is too short and lightweight for long life so it would be informational anyways. I probably won't test it to be honest. Unless I get bored.
So much bullshit in one post it’s hard to know where to begin. Cable wimpy and short? It’s properly sized, and comes in a 24’ length. Might test the G3 at 277 for laughs? The spec is 200-240 on the spect sheet in the immediately preceding post. Why put a disconnect at an AC unit? Because it’s ****ing code.
440.14 Location. Disconnecting means shall be located within sight from and readily accessible from the air- conditioning or refrigerating equipment. The disconnecting means shall be permitted to be installed on or within the air-conditioning or refrigerating equipment.
I’m done with arguing on these points:
1. Follow Manufacturers’ installation requirements
2. Follow the NEC. Almost all situations are covered.
3. When there’s any bit of gray area after consulting 1 and 2, contact your local AHJ for their guidance.
If anyone wants to ignore advice on any of those, feel free to go ahead. Happy to discuss any specific install questions or offer advice on that, but not going to argue points 1-3 anymore.
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Actually the Gen 3 is only 18' long. (They shortened it by 6'.) But that is still plenty long enough for most installs.
MXLRplus
Active Member
The Gen2 HPWC manual 2020: https://www.tesla.com/sites/default...nstallation_manual_80A_en_US.pdf?201612081439 says: Voltage and Wiring - 208V or 240V AC single-phase: L1, L2, and earth (pg 5)
You're right, I'll continue to ignore instructions. I'm running 277. Tesla doesn't discuss 277 anymore for reasons they wish to keep private. Perhaps because both Wye and delta 480 can freak out the unit if you have no neutral? Or people were using the ground as the neutral? Who knows? Tesla claims it's not stable, but I somehow doubt that with several hundreds of 277 installs.
Note: The AC units are circuit protected up there, not simply at the panel, the circuit trips up there first. Kind of like all serious equipment does. A HPWC is protected digitally. If it tries to pull too many amps it errors. 3? errors and it quits.
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Yup, you're totally right. Wrote this before my morning coffee. Thanks!
If by "nobody" you mean, "everyone who doesn't bother to check the wire gauge if they need more current"--well, sure....
MXLRplus
Active Member
If by "nobody" you mean, "everyone who doesn't bother to check the wire gauge if they need more current"--well, sure....
If it's a simple situation sure. But say I see 10g wire for receptacles or lighting coming from the panel, but there is only a 15a breaker I'd careful. Ditto for commercial circuits.
Btw, does anybody has an info when the Gen3 TWC is offered in Europe. I have 2 TWC's with faulty cables and am postponing the replacement since some months, resulting in some additional trips to the local SC . Also does someone know where they are produced, in Buffalo where the production is already online or in Fremont, where we have still a Corona related lockdown?
. Also does someone know where they are produced, in Buffalo where the production is already online or in Fremont, where we have still a Corona related lockdown?
TT97
Active Member
Btw, does anybody has an info when the Gen3 TWC is offered in Europe. I have 2 TWC's with faulty cables and am postponing the replacement since some months, resulting in some additional trips to the local SC
The Gen 2 are made in China (or at least mine was), I imagine Gen 3 is likely made there as well.
Hey so they actually sent us Gen2 units so the swap was pretty quick and painless and didn't require replacing the breakers, but during the install I got to thinking...
Could you run the Gen2 units with 100amp breakers (and the existing wiring that supports up to 100 amps) but set to output say, 32 or 24 amps from the HPWC? Changing the HPWC output is just a little switch inside the unit. Still code if you do this? The panel has 400amp service so it wouldn't be bottlenecked anywhere but by the HPWC output setting.
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