This is exactly what I did, probably another Tesla in the future
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Just had a Tesla charger installed. Charges are going at 12 amp at 246 volt?
- Thread starter Niroc
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This is exactly what I did, probably another Tesla in the future
EfficientWatts
Member
Same here. Could have done 6 awg, but because my run was so long (48') the price difference for moving up to 4 awg was relatively small. I did go a different route (14-50 outlet) as I don't know my long-term plans at my current residence. Completely overkill especially since I have the Gen 2 UMC at 32 amps max but I do get some sweet voltage levels while charging haha.
Well, I’ve got 10 years left on the mortgage, so I’ll be here at least that long.... we decided 2 years ago that we’re here at least into retirement; and even then, we’ll likely snowbird down south at the most.
To quote Gabby Johnson - “I was born here, an’ I was raised here, and dan gum it, I’m a’gonna die here!”
Nothing wrong with that. He might buy a second Tesla and it could balance on a higher Amp than 60A total. Don't know what #4 THHN, in conduit rating off the top of my head
Don't know what #4 THHN, in conduit rating off the top of my head
Not a google jockey like all of the folks over at the M3 forum electrical threads. But I will admit I looked at my trusty ampacity chart in my toolbox and #4 THHN is showing 95A, which is the same as the XHHW-2 cable I deploy on some of my Gen I HPWCs with dips set at 72a charging on a 2-pole 90a breaker.
I know most electricians are know-it-all’s, but I still believe that if owners are well versed about these slickly designed Tesla Gen 1 HPWCs and Gen 2 WCs and about their operation and adjustability, they can have a productive conversation with their installer to help insure a proper and safe installation on the first attempt.
I dunno about these lesser than full tilt 48/60a installs, but after the first year of my 72/90a and 80/100a installs, i de-energize the load center, turn the breaker off, triple check with my tester to insure power is dead, and then re-torque all connections on this high amp circuit just to be safe.
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I agree. It's like knowing as much as you can about meds or medical procedures before you talk to the Dr. Don't trust the electrician to know everything.
Correct.
Unless your electrician only put in wire good for 35a but used the “next size up” breaker rule to put in a 40a breaker.
That is extremely unlikely though.
I thought that I read for a sr+ you should use a 40 amp breaker so that is what I requested to have installed. Assuming that the wiring is correct, the correct setting is 6 (32 amp)?
eprosenx
Active Member
While #4 THHN is rated to 95 amps at the 90c insulation rating, typically the breakers and terminals on the Wall Connector would only be 75c rated, so that means an 85a limit. Since there is no 80a (64a continuous) setting on the Wall Connector, you would just want to do an 80a breaker (or below) and set the Wall Connector to 80a (or below). (note that I am making the assumption that we don't need to derate the wire due to ambient temp or wire fill or distance...)
For a SR, SR+, or MR, you only have a 32a onboard charger. You can max that with a 40a circuit. But typically if you do a 14-50 receptacle we would recommend you wire it for a 50a circuit and use a 50a breaker (it is fine that it is more than what you need since the receptacle, wire, and breaker would all be rated to 50a).
So now this opens up more questions: If your Electrician was good/nice and they wired you with 6awg NM cable (or better yet 6 awg THHN in conduit) you could actually swap to a 50a breaker or 60a breaker (in the THHN scenario) and set the Wall Connector to match. That would future proof you for some later vehicle you might buy (but it would make zero difference to your SR+ today). If they wired you with 8 awg then you need to stick with the 40a breaker and are limited to 32a of charging speed (which is probably plenty).
If you can *safely* take the cover off the Wall Connector and/or the breaker panel and post pictures here we might be able to help identify what size and kind of wire was used. But really, this is something to discuss with your electrician since we can not necessarily see everything about the cable path in a couple of pictures online.
davewill
Active Member
Yes. I would have went ahead and had a 50a circuit put in, myself, but the 40a will work just as you say, maxing your car's charging capacity at 32a..
Yikes, if you are correct (and I have no reason to doubt you) it appears that I have mismatched components for over 6 years running, and I will once again with tomorrow’s install even though I have passed inspections. After being satisfied with reasonable temps at all connection points (even while tested at a wide open 100/80a) as verified with an IR gun, all operates very well with the 6ga. charge cables and handles getting the hottest by far on my HPWCs. I suspect their is a rather large amount of cushion inside the overall WPWC and WC design in that all 2012 and very early 2013 HPWCs had to have their 100a fuses replaced with 200a fuses to function properly.
I believe the wall connector manual states to use the 75C rating for the wire. So this would be 85A on #4 THHN. I don’t believe most residential breakers are rated for 90C operation as well. Personally I’d take the 60C ratings for anything anticipated for a continuous load, and then oversize from there to try and hold under 3% total voltage drop across the service. Or more often the breaker or load has a max listed conductor size and I just use that. It’s really all about acceptable risk. The 90C ratings are very conservative relative to the absolute limits for the conductor. The NEC is there to accommodate typical installs, and ensure a good useful service life. This means not all connections are perfect, conductors can be damaged on install, and sometimes a strand or two might even not be connected on stranded conductors. The code isn’t there so that an ideal install just barely works, it’s to ensure the majority of installs last a long time trouble free.
The wire inside the handle going to the car looks to be #6, so it’s not really terribly dangerous to run it on #4, even if it’s not code complaint for the application. But the code is there for a reason, and thermal cycling is more likely to create high resistance connections as the thermal gradients increase. And this will be presumably non linear across conductor sizes.
The wire inside the handle going to the car looks to be #6, so it’s not really terribly dangerous to run it on #4, even if it’s not code complaint for the application. But the code is there for a reason, and thermal cycling is more likely to create high resistance connections as the thermal gradients increase. And this will be presumably non linear across conductor sizes.
eprosenx
Active Member
Yeah, I can promise you that this is correct. Just goes to show you how inspectors constantly miss stuff! (even really basic stuff like wire ampacity!)
The code reference is table 310.15(B)(16). You can register for free access to the 2017 NEC (NFPA 70) on their web site.
Regardless of the wall connector design, the breaker also will have that 75c terminal limitation (stamped on it).
There are safety margins built into things and you are likely consuming some of those margins. 4 awg copper in conduit is only good to 85 amps landing on 75c terminals. (assuming no ambient temp or other adjustment factors). You need 3 awg copper for a full 100a.
You should change the setting on anything using 4 awg in conduit down to 80 amps and replace the breaker with 80a ones.
Voice of experience here. Don’t assume a Tesla recommended electrician knows what he Is doing. In my case he installed a standard duty breaker on #8 Romex with a light duty receptacle for a 50 amp circuit. The result nearly caused serious damage to my house. ALL OF THIS IS COMPLETELY AGAINST CODE FOR A CIRCUIT DRAWING 40 AMPS CONTINUOUS LOAD. I now have a commercial breaker on #6 and a commercial rated receptacle. These parts cost about 5-10 times the cost of Home Depot stuff. A circuit drawing 40 amps continuous is not a casual endeavor for do it youselfers
Unless I needed the extra 8 amps, I would have just switched to a Gen II MC which would keep you safe and and kept my Gen I UMC in the trunk for road trips.
So glad you caught the mistake before a serious calamity ensued!
davewill
Active Member
He paid to have a 50a circuit installed, why should he accept a 40a circuit, instead?
If you really wanted the safest solution get rid of the receptacle all together and use a Wall Connector.
Oh and I'd take a 50A GFCI Breaker from Home Depot over any commercial breaker on a 50A receptacle near where my car is parked.
I'm sure your commercial breaker is a GFCI? I worry more about people than my house.
I can’t disagree, however, I love my receptacle charging 14-30 (~80,000 miles), and now my 6-20s that charges both the S and M3 using a Gen II WC. The HPWCs were for PlugShare users (back when “supers” were rare), and are now mostly for old timers with 72 and 80 amp capability guests along with a 6-50.
I have two home charging installations at two locations. And I didn't know much when I installed my first setup (the 14-30, I certainly could have done worse). One install is a Wall Connector 40A is outdoors but out of direct weather. Another is a 14-30 which works fine (with dedicated UMC Gen II) and this is indoors and does have a GFCI on it (even though it's never unplugged). It didn't used to be code to require GFCI on EV Charging (but I applied common sense
), It is code now. I might swap out the 14-30 for a 2nd Wall Connector. I don't plan on increasing amperage so it doesn't buy me a whole lot. In hindsight, higher amperage would be more convenient (and my daily commute is 10 miles round trip). Charging at the 14-30 site is "free" (Solar), there are times I can't get juice in fast enough to use it and have to charge at my other site (~$0.25 kwh or SC ~$0.25 kwh). I like a full battery (90%) to get to the other site (and back) on weekends on the free electrons.If I could do everything over from scratch, I would have put in a 20% larger Solar (not allowed based on my current usage before EV). Upgraded to 200A service (I only have 100A which is generally plenty for my needs even with EV). And installed a 60A Wall Connector. The 40A Wall Connector is on a 150A Service and could have easily been 60A. But that site, 40A is plenty (because I use it at little as possible without Solar and high kWh cost).
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Actually I have a wall connector on a heavy duty pigtail. There are times when I need to be able to use the circuit otherwise like when the wall connector fails. When plugging or unplugging, I kill the circuit so there is no arcing. Just using a 32 amp cord is absolutely no solution. You need what you pay for, you need it safe, and you need it to code. My second house fire was a result of an electrician shortcutting. If that has happened to you, you wouldn’t be casual about such things either.
davewill
Active Member
Truly just being unplugged from the car is sufficient. The current draw of the EVSE by itself is pretty minimal...but if it makes you more comfortable to switch off the breaker, go ahead.
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