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I'm going to say yes... you're dumping almost 1kwh into the wires/outlets in that circuit. If you're using a really long run that heat's spread out over a lot of wire and probably not much to worry about, but even so I'd find someone with a thermal camera and see what's heating up.
Long run is actually bad. Otherwise, we should all make our electrical runs loop around the house a few times.
You need to go to Skillshare and take some lessons on electricity. Or you can go pick up a pack of extension cord at the store and read the labels. Longer runs tend to make the wire run hotter. .. meaning shorter run would run much cooler.
Bad.
Compare:
#16 wire pushing through 120V @ 8A for 3 ft (AKA Short).
#16 wire pushing through 120V @ 8A for 300 ft (AKA Long).
Which one will burn the house down?
I believe that 20a/240 would cover the vast majority of my needs
Agreed. I had a detached garage with a dedicated 20 amp outlet I could repurpose (with 12/2 wiring), so the breaker was swapped for 2-pole, and I charge at 16A 240v = ~12.8 miles/hr., or 100 to 150 miles per night. I average less than 125 miles per day, so it's not a problem. To go beyond that, I would either need to trench a new feeder (& probably upgrade the house to 200A), or have a second utility service added in the garage.
I appreciate your interest in my education!
My understanding is that the current carrying capacity of a wire is based on the gauge of the wire and the insulation of the wire. Narrow wires have more resistance and thus heat up more than larger gauge wires for the same current. Also some wires such as those made of aluminum will have higher resistance than others for the same length of wire and so will have a different current rating.
The thing we don't want to happen is for the insulation of the wire to fail. That typically happens when the wire gets so hot it damages the insulation, but sometimes it happens if the wire is chemically or physically attacked. It also happens at junctions where you can have poor mechanical junctions. The areas with higher resistance will heat up and typically that heat causes even more resistance and you have a thermal runaway and the wire melts (or it trips a circuit breaker). If the higher resistance is spread across a large surface area, you just get ... heat, which is wasteful but not specifically dangerous unless there is so much that it harms the insulation. Another concern may be heat cycles where junctions will work their way loose and you then get an under-speced joint (see thermal runaway). Heat cycles are especially a concern if you're joining dissimilar elements (aluminum/copper) as they'll expand at different rates and potentially work their way loose and (see thermal runaway).
So a wire with insulation that copes with high heat may be allowed to have a narrower gauge. Let's say your contractor put some narrow gauge but high temperature wire under your driveway. It is "safe" but will heat up more than is "ideal" but if the alternative is to dig up the driveway, you may just live with it. Just like an extension cord may heat up over a long run (and cause a voltage drop!) but it is fine because you want to plug your Christmas lights in and there isn't a convenient plug on this side of the house.
Oh, and you shouldn't test a circuit by licking it.
How'd I do?
.... why would a fire start if you start charging at 110v? Resistance + Current makes heat. The car limits current to what the line can handle. If the resistance is low there's no heat.
Like I said... it's voltage DROP that's important. If you're pulling 12A and voltage drops from 125 to 110v that's 180w being dumped somewhere. If voltage drops from 110v to 108v that's ~24w being dumped somewhere. It's voltage DROP that's the critical value.
Never use wire in a wall and rely on the insulation rating as the factor, never.
Thank you for that clarification -- yes it is my understanding that running a wire where the current is based on heat-tolerant insulation has a large number of provisions (in a conduit with other wires, in a wall, etc). I didn't mention that even though I should have.
To be honest insulation rated wires seem like a dicey proposition in almost any situation. I can imagine uses, but I'd have to work pretty hard to justify them.
Regardless, I suspect that code is not actually completely reasonable for EV charging -- there are too many areas where running a circuit at 80% of maximum capacity for hours at a time will expose imperfections, especially once you wander past 30a. I suspect there will be added provisions (with the teeth of "insurance companies will deny claims") for things like "NEMA attached devices may only draw 60% of the circuit/plug's rating" (see also: 32a on a NEMA 15-50).
Thank you for that clarification -- yes it is my understanding that running a wire where the current is based on heat-tolerant insulation has a large number of provisions (in a conduit with other wires, in a wall, etc). I didn't mention that even though I should have.
To be honest insulation rated wires seem like a dicey proposition in almost any situation. I can imagine uses, but I'd have to work pretty hard to justify them.
Regardless, I suspect that code is not actually completely reasonable for EV charging -- there are too many areas where running a circuit at 80% of maximum capacity for hours at a time will expose imperfections, especially once you wander past 30a. I suspect there will be added provisions (with the teeth of "insurance companies will deny claims") for things like "NEMA attached devices may only draw 60% of the circuit/plug's rating" (see also: 32a on a NEMA 15-50).
50A breaker+wire+receptacle for 32A EVSE is probably a good recommendation. That's what I thought when I had my 240V installed. If you need faster charging than 32A, probably time to get a DC charger installed.
Have only had my model S for one month and was intending to only use superchargers but have now read it is recommended to charge constantly. Will charging at home on a 110 and also using the superchargers when I want quicker charging be ok to maintain the battery?
If you have the time 110 is fine, it is also much better for your battery as it charges slowly and therefore much less battery degradation Compared to the 220 V system, although 220 is probably a bit more efficient and certainly more convenient.120 volts, not 110. And here come the cows, moseying on home. I've made no argument for 120v over 240v, that wasn't the point. Use whatever you want, what works for your situation and what is convenient. In truth, it makes no difference for battery life, 120v 16 amps or 240v 48 amps, for example, slow is slow, how patient can you afford to be? I wouldn't go out of my way to use a 120v circuit but if that's what you have and it serves your needs/works in your situation, no worries. There is no disadvantage to the 120v except speed, which as I said is exaggerated at low temperatures. The dogma here is a 240v circuit is a minimum for home charging. I don't disagree with that as a practical matter and for convenience. And if you are installing a circuit, by all means, install a 240v circuit. On the other hand if you need to use a 120v circuit and your circumstance allows, it's just fine.
I’m not sure why you bumped a 2.5 year old thread for this advice, but this is just false. I’d argue there’s precisely zero measurable difference in “battery degradation” between 120 and 240v AC charging of any speed.If you have the time 110 is fine, it is also much better for your battery as it charges slowly and therefore much less battery degradation Compared to the 220 V system
Correct. If anything 120V charging is worse because it uses more energy (car systems must be on when charging, and these very little energy left over for actually charging the battery).I’m not sure why you bumped a 2.5 year old thread for this advice, but this is just false. I’d argue there’s precisely zero measurable difference in “battery degradation” between 120 and 240v AC charging of any speed.
The US has been on 120v and 240v since sometime last century. Regular outlets are 120v unless you are in some weird sort of setup where there isn't modern electrical service. Occasionally you'll get someone that is on 3 phase power that has lower voltages on regular outlets because they are in a business setting (condos on the edge of a business district in Canada, or a loft apartment over a business in the US) but those are rare.If you have the time 110 is fine, it is also much better for your battery as it charges slowly and therefore much less battery degradation Compared to the 220 V system, although 220 is probably a bit more efficient and certainly more convenient.