Bugeater
Member
Thanks Henry. Even though I'm pretty careful and knoweledgable about electricity, it really sounds like the effort isn't really worth the return it would provide.
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m6bigdog
Member
That will never happen!! Not in your lifetime...
Extension cords and supplying two sources of power to a single device (EV, EVSE etc.) is not allowed by the NEC.
Also the receptacle polarity is not specified, guaranteed or defined so they could be opposite on each receptacle producing a short between phases. KaBOOM!!
Also, just because there are two receptacles doesn't mean you can draw anywhere near a balanced current from them.
That is, based on the voltage drop in each branch circuit wiring you may only be able to draw full current through 1 of the 2 receptacles if the circuits are summed together at the charge port!!
Olle
Active Member
Electrical code question:
Can I run two parallel NM-B 6/2 from my 100A breaker to the HPWC? That would give a sum of 110A allowable ampacity.
Reason for this question is that the highest NM-B (on 2 awg) ampacity I've seen is 95A,
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet6
which would be illegal on a 100A breaker and I was hoping not to run conduit inside my wall.
Can I run two parallel NM-B 6/2 from my 100A breaker to the HPWC? That would give a sum of 110A allowable ampacity.
Reason for this question is that the highest NM-B (on 2 awg) ampacity I've seen is 95A,
http://www.southwire.com/ProductCatalog/XTEInterfaceServlet?contentKey=prodcatsheet6
which would be illegal on a 100A breaker and I was hoping not to run conduit inside my wall.
Umm... It's already happened. I dismantled mine but I know a couple other people still using theirs at campgrounds (at 70A). I think you meant a commercial version that you can buy will never happen.
Not sure what you mean by KaBOOM but that won't happen. It's a little different at 3-phase locations (won't work at all). In any case, you have to have a method of determining the phase polarity and the device as implemented in the fore mentioned threads has an automatic method of doing this. Believe me I'm not recommending anyone pursue this. I agree it's a bad idea. But you won't cause an explosion.
Yes, the receptacles have to have reasonably similar cable lengths but they don't have to be exactly the same. The system is self-balancing to some degree. It's very rare that the resistance is so different between the two that you end up tripping a breaker. Breakers can fail in the closed position, although everybody who did this had redundant breakers. Look at how it was implemented.
I agree with you it's not something we should attempt. I also don't want to spread incorrect information.
The NEC does allow you to use a lower rated wire/cable than the circuit breaker rating protecting the circuit. But there are exceptions for this and I do not recommend doing this.
I'd like to explain circuit breaker sizing.
A 100 Amp breaker is rated for only 80% of its rating (80 Amps) for continuous loads (charging in my opinion would count as a continuous load since it can be longer than 3 hours to charge). You can get a 100% continuous rated 100 Amp breaker that is rated to handle 100 Amps (continuous) but you need to make sure your breaker is a 100% rated breaker.
I just installed a 100 Amp circuit breaker in a 200 Amp panel. Residential installs don't require conduit. You need to take into account voltage drop when sizing your wiring conductors (the greater the length of conductors, the greater the voltage drop). I suggest you get a licensed electrician to help you our or just consult a Professional Electrical Engineer (I am one) to figure out your wire size.
The NEC requires that a disconnect be located within sight of the load. I am not sure if the wall charger has a built-in disconnect (it has to be a mechanical means of disconnect) so I put in a 100 Amp non-fusible disconnect that is a 3 pole disconnect since the wall charger requires a neutral and 2 power (hot) conductors. Be sure install an equipment grounding bar and equipment grounding conductor with the disconnect. Also run an equipment grounding conductor for the wall charger. This will protect you and the MS against a ground-fault. The equipment grounding conductor needs to run back to the grounding bar in the panelboard. Do not install a ground rod at the wall connector unless you bond it to the service entrance ground (located at the main panelboard in your home). The disconnect can be non-fusible since the circuit breaker provides the overcurrent protection.
I hope this helps. Please be sure to check your local codes and do not take what I have stated in this post as the code in your area without consulting a Professional Engineer, licensed electrician or the Authority Having Jurisdiction (building department plans examiner, electrical inspector, etc.).
I've been wondering about this same question. Tesla gets away with it in their cables which makes them feel smaller and more flexible.
Actually the Wall Charger does not require neutral and there's no place to attach one. It requires hot, hot, ground. Most people only install a 2-pole disconnect and most inspectors will allow the breaker to qualify if it's within sight of the HPWC.
m6bigdog
Member
The HPWC 100 amp circuit has an ampacity of 80 amps (100amp * .8 = 80 amp continuous) so the #2 AWG wire is good.
Parallel wires in the NEC is a rare exception and a branch circuit is not one of them. Also, only one wire can be used in a breaker terminal and splices are not allowed in the load center.
I don't believe this last statement is true (agree with all your other points). Can you tell me what section of the NEC prohibits splices inside the load center?
To Olle: In in case it wasn't clear from m6bigdog's answer, no, you are not allowed to run two #6 instead of one #2. That would be a violation of the NEC.
All righty, you twisted my arm....I got one! ahhaah. The deciding factor for me was to find an electrician willing to not charge me double the price just to install this wall charger over a NEMA 14-50. Found one that only got 100 bucks more. Lol!
One guy quoted me 850.00 for NEMA 14-50 and $1600.00 for the HPWC. It was one of the electrician from Tesla recommendation list. Found one off yelp with excellent review, licensed, and will pull the city permit, etc., for 800$ to do the HPWC on an 80a or 100a switch.
Question: If I have a Model S w/o dual charger and use this Wall Charger, do I have to set some dip to 40A per discussion in this thread (Wall Connector Installed Today) and change the DIP SWITCH again if I ever get a dual charger on the Model S?
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davewill
Active Member
No. Set DIP switches in the HPWC to match the circuit breaker, not the car. The HPWC advertises it's maximum, and the car draws the lesser of the HPWC's max amps and the car's max amps. That's why public L2 stations (whether Tesla or J1772) can be used freely with any car that can plug in. A Model S with a single charger will limit itself to 40a.
The answer is no. NEC 310.10(H). Only conductors of gauge 1/0 and higher may be paralleled except in special circumstances.
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#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.
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However, the wire/cable MUST be rated for the full load. If you have an appliance that requires a circuit rating of 100A, you may NOT use a 95A-rated cable and the accompanying OCPD "upgrade" (240.4) to go to 100A. You size the cable to the appropriate load, then protect it with the proper breaker (which can be the next trade size larger, if the load is not a standard trade size).
There are exceptions to this - Chicagoland requires conduit and some select New Jersey & New York cities still require conduit for all electrical infrastructure.
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Appliances don't follow NEC, which is for infrastructure wiring. The HPWC uses a #6 wire for 100A requirement, which would be illegal in an infrastructure install.
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For what it's worth, one AHJ near me allowed the circuit breaker in the basement to act as the article 625 disconnect as long as the entire panel was lockable. Yet others have demanded one near the HPWC. This is one where you're going to get many different interpretations.
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Splices are indeed permitted inside load centers. Many times, this is how generator panels are added after the fact - the existing circuit wires are spliced and carried into the transfer switch panel. They may not be pretty, but they're permitted.
Olle
Active Member
thanks FlasherZ! You sound like one who really knows what he is talking about.
Thinnest legal means of connection that I can find then is two #3 THHN with #8ground in a 1" conduit (just under 40% fill). Minimum 5" bending radius! Anybody disagree?
For 80A charging / 100A breaker, this is correct (assuming copper). 5" bending radius on continuous raceways (there are some other options you have with surface-mounted rigid conduit and pull elbows, but the cover must be accessible, and it wouldn't be very thin). Thinnest is going to be EMT on the raceway IMO.
FlasherZ, thanks for your recent posts. I agree with others; you know what you are talking about!
I ran the wall charger cable in conduit anywhere I felt NM cable would be exposed to potential damage.
And as someone pointed out earlier, the wall charger does not require a neutral. I ran the neutral and went through a 3-pole disconnect since I will be feeding NEMA 14-50 receptacles and these receptacles have a neutral.
I got the Tesla wall charger today. I would like to mount the charger in the midpoint of where the MS will be located in the garage (still waiting on the MS to be delivered). This is not the location that Tesla recommends. I am concerned about having the charger near the garage door and having rain, snow, etc. on the charger and cable while charging the MS. I understand the wall charger has a NEMA 3R rating (this means it is somewhat weatherproof). Anyone have comments on locating the charger near the middle of the MS?
I have not checked yet....but does the wall charger connectors allow both Aluminum and Copper conductors? I am considering aluminium conductors but understand that connectors need to be rated for Al or Al/CU (Aluminum/Copper).
Thanks.
EVSteve
110% Solar Powered
I would be very surprised if anyone would be able to run the proper size Aluminum into the terminals. They are very tight. I highly recommend just running the appropriate gauge copper. The cost savings are not worth risking a fire.
chriSharek
Member
I totally agree. The #4 I ran barely fit in the HPWC. I can't even imagine trying to get #3 in there for the 80 amp circuit/100 amp service.
I don't have a usable garage, so mine is mounted on the exterior wall of my house. Haven't had a problem yet. Can't imagine you'd have an issue putting it inside your garage near the door.
+1. There is not much space to work with inside the HPWC. The only reason I ran #3 instead of #2 was to make it easier to work with. Also, Alluminum is usually far more rigid, making the turn up to the terminals very difficult even if it did fit.
I ended up running oversized Al to a subpanel in the garage, then #3 from the sub panel to the HPWC. The cost difference is not much. The only challenge might be finding #3 copper as it's not as well stocked as #2 or #4, but still plenty of places to get it (I found it online).
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As far as the mounting location is concerned, the HPWC has a 25 ft cable for a reason - to make the mounting location more flexible. Just find a space that is convenient for you. I have mine mounted between the garage doors.
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.
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