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At 60c or aluminum. I was thinking of an indoor garage run, but you’re correct on that in certain installations.
Ok, so the Rivian Portable EVSE is programmed to provide up to 48A if the truck requests it. The only limiting decision logic in their included EVSE is actually the adapter. The adapter itself instructs the actual amperage limit (passively by a resistor or magnet placement, or perhaps has a chipset inside for simple communication). I would have only expected that the adapter only presents an identity, like "adapter A" and "adapter B". Upon recognizing which adapter is in use, the EVSE would then chose the corresponding current amount, such as 12a or 32a.
You do?
Then you won't understand these posts. For starters an outlet is a connector that you plug a device into. Second, devices that are considered continuous loads may onlly be plugged into an outlet that is rated for 125% of the device load. thus an EVSE that draws 32 A must be plugged into an outlet rated 40A.
The Rivian portable EVSE only advertises a maximum rate of 32A (It's written on the label). The wiring in the cordset is 10AWG 105°C rated, but you don't really want it to be hot to the touch, which it would be above 60C. You couldn't safely draw much more than that with that size cable because of that.
The EVSE is just a contactor (relay). All t does is connect the vehicle to the line. But it also does checks on the connection to the mains to be sure that there is a valid earthing path and that the EVSE senses the "presence" of a vehicle before turning on and will inhibit closure of the contactor if these consitions are not met, if it senses an earth leakage fault or if the temperature of the plug gets too hot. And it has one additional very important job. It tells the vehicle how much the vehicle can draw from the power supply it is connected to. This it signals to the vehicle by transmitting to it a ±12V square wave whose duty cycle corresponds to the allowable current.
If the EVSE is permanently wired to a circuit of a particular size the EVSE is set permanently at comissioning to send the proper duty cycle signal over the control pilot circuit to the vehicle. This can be done with a rotary switch (Tesla Gen 2), DIP switches (Rivian wall "Charger" or by writing the level into rom (Telsa Gen 3). A mobile EVSE can plug into a 5-15 outlet (max current 12A) a 5-20 outlet (max current 16A) a 6-50 or 14-50 outlet (max current 40A unless you want to be sure you stay code compliant if the 14-50 is on a 40A circuit in which case the max is 32A) etc.
I'm not saying either of those things because I don't know which of those 2 possibilities has been implemented. I do know that the Rivian adapters have 5 pins just as does the J1772 connector does so the individual adapters could be generating all the control pilots but I do not know that.
Not in detail but if you'd like to get a general feel for J1772 just look it up on Wikipedia.
That's what it advertises and that's what it delivers but it must be supplied by a circuit rated for 40A. We can carry on about this 'til the coes come home but the essential fact here is that these are the rules. They are written by insurance people who are using a belt and suspenders approach here to minimize the probability of fire to many 9's.
It doesn't request a charge rate on L3 either. What it requests is a voltage and it keeps upping that voltage monitoring current until it gets the charge current it wants. it has been informed by the EVSE how much mains current the connected circuit can supply. It will not request a voltage increase once that mains current limit is reached. f course the current limit can be anything less than the rated current as set by the operator via the vehicle software.
Yes. Since the circuit is not rated for 125% of the continous device load of 15a, I would expect the 15a breaker to eventually trip.
I was specifically asking about the Rivian portable EVSE that is included with the truck. It seemed that you were saying you only need a different adapter to pass more than 32a through that EVSE. Now it seems you must have been talking about some other EVSE.
The circuit breakers used in residential applications have two tripping mechanisms. The magnetic trip is designed to clear faults (such as a short). The thermal mechanism is designed to de-energize overloaded circuits based on the size of the overload and its duration. A 15A load on a 15A breaker will never trip it. A 30A load on a 15A breaker will trip it in about 2 minutes. a 16A load on a 15A breaker will trip it in about 2 hrs etc. Note: the actual times depend on the class of breaker. Obviously things are done this way in order to allow appliance inrush current to be accommodated without tripping.
The NEC is written by the NFPA which is a consortium of individuals in the insurance and electrical industry. Its goal is to minimize the probability of fire (National Fire Prevention Association). Probability is a concept that most people don't understand hence, I think a lot of the confusion when people are confronted with it. The more current that flows is a circuit the hotter it gets and the hotter it gets the higher the probability of fire. If you reduce the current in a circuit by a factor of 0.8 the heat developed per unit time goes down by 36%. The temperature reached depends also on the time over which the heat is being developed, the insulation, the confinement, the ambient temperature etc. This is why we have the 80% derating requirement for loads that are on 3 hours or more.
I was speaking of EVSE in general. They are required to transmit a square wave that tells the vehicle how much current it can take from the EVSE. It is entirely plausible that Rivian will eventually off other adapters for other common 120 and 240 plugs.
I have not checked the wire size so I do not know. Other people sell portable EVSE (and I have recommended that Rivian owners consider the Tesla UMC in order to be able to access more outlet types) that will authorize 40 or even 48 A.
My old senior EE told me that you are specifically not supposed to rely on a breaker tripping as part of your safety plan when designing power electronics. That it won't pass regulatory body muster and get approved. Not sure if that's the case, but given how many houses in my neighborhood and around the world have circuit breakers in them that are known to not always trip properly, it feels correct. I wouldn't rely on a circuit breaker as my primary/only line of safety. The circuit breaker should be the suspenders (or rope over your shoulder) that don't let your pants fall down, only to be used after you have properly fitted pants and a belt on as your primary means.
That's definitely the right way to look at it. We killed a 30A breaker with a tt-30 at one of the campsites we stayed at after having plugged my adapted rivian portable in without adjusting the current down from 32A right away. Luckily it tripped dead instead of getting stuck on. I realized quite soon after first plugging it in that I hadn't changed the current limit, but it was too late by then.
