Some Canadian J1772 are 70 amps. If I use a J1772 adapter and connect the P85 (US model) to such a connection, will the adapter limit the amperage to 30 amps?

The onboard charger is the limiting factor, not the J1772 adapter. If you have the dual charger option, you will be able to handle 20kW ( 240 V @ 80 Amps )

And just for completeness: If you don't have the dual charger option, you'll be limited to 40 amps (~10kW), not 30 (~7kW).

I recently installed two 100 amp J1772 stations at my office. They can deliver 80 amps continuous. I have the twin chargers and it works beautifully with my J1772 adapter. Of course if you only have the single on board charger, all you'll get is 40 amps.

Be careful about whether EVSE's are described by Circuit Breaker rating or output current rating. Sun Country Highway and their major supplier, Clipper Creek, label and describe the EVSE's by the breaker rating; this is often typical in Canada. To avoid popping conventional circuit breakers, it is strongly recommended that continuous loads not be run at more than 80% of breaker rating. Therefore a 100A circuit can feed an 80 Amp J1772, a 50A circuit can feed a 40 Amp UMC, etc. In most U.S. locations, EVSE's are described by their output current rating. On top of that, Tesla has some protection software in the MS that attempts to detect "weak" circuits and reduce the current by another 25%. Therefore, a 50A circuit, that should provide 40 Amps through a UMC, might be declared "weak" by the car and the charging current reduced to 30 Amps.

US and Canadian electrical codes have definitions for "continuous load" and EV charging fits in to that category. In a "continuous load" scenario, current is limited to 80% of the breaker capacity by code. It is more than a "strong recommendation", and is why a 100 amp Clipper Creek EVSE will only deliver 80 amps. Having said that, you're right about the confusion. It probably makes more sense to talk about the output current. Even in Canada, the Chargepoint, Schneider, Eaton, GE etc. stations show their output current, not the input breaker size. It does seem to be a Sun Country/Clipper Creek phenomenon.

The J1772 connector is the limiting factor here. It is limited to 80 amps and is not certified to deliver more than that.

Better yet, talk about output power. 80 Amps at 208V is (obviously) less power than 80 Amps at 240V, but 16kW is 16kW. I realize that EVSE manufacturer's do not control whether their equipment is installed on a 208V circuit or a 240V circuit, but on sites like Plugshare, it makes sense to state the power (kW) output by the EVSE for that location.

The wiring is rated for 100% current. It is the vast majority of thermal/magnetic circuit breakers that are limited to 80% of rating for continuous loads to avoid false trips. Although rare, there are circuit breakers that are rated at 100% continuous load. In fact, Tesla uses them in their "Distribution Centers" at Supercharger Sites. Here is an excerpt from Page E5 of the Madison, WI Supercharger Plans. The Madison Supercharger uses 120 kW Superchargers. With 90% conversion efficiency they can draw a 133 kW for a long time with two cars connected. With a 3-Phase, 480 Volt supply, that requires a continuous draw of 160 Amps, which is about 92% of the breaker setting of 175 Amps. This is OK, because these Schneider/Square-D Powerpact breakers are rated at 100% of load; I added the red highlighting to the figure above. BTW, these are pretty amazing breakers. Tesla can read their state remotely and reset them remotely!

Right. This is what I was referring to (from the Canadian codes, but US are similar). The SCH / Clipper Creek units are all built for 100% of their rating. The wiring is rated for 100%, but according to code, can't be utilized at 100% in a continuous duty application. The breaker, as you say, would trip after a few minutes of 100% load. It is also worth noting that the J1772 standard, I believe, is limited to 80 amps. Section 86 — Electric vehicle charging systems 86-302 Connected load The total connected load of a branch circuit supplying electric vehicle charging equipment and the ventilation equipment permitted by Rule 86-300 shall be considered continuous for the purposes of Rule 8-104. 8-104 Maximum circuit loading (see Appendix B) (1) The ampere rating of a consumer’s service, feeder, or branch circuit shall be the ampere rating of the overcurrent device protecting the circuit or the ampacity of the conductors, whichever is less. (2) The calculated load in a circuit shall not exceed the ampere rating of the circuit. (3) The calculated load in a consumer’s service, feeder, or branch circuit shall be considered a continuous load unless it can be shown that in normal operation it will not persist for (a) a total of more than 1 h in any two-hour period if the load does not exceed 225 A; or (b) a total of more than 3 h in any six-hour period if the load exceeds 225 A. (4) Where a fused switch or circuit breaker is marked for continuous operation at 100% of the ampere rating of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed (a) 100% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 2 or 4; or (b) 85% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3. (5) Where a fused switch or circuit breaker is marked for continuous operation at 80% of the ampere rating of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed (a) 80% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 2 or 4; or (b) 70% of the rating of the circuit where the ampacity of the conductors is based on Column 2, 3, or 4 of Table 1 or 3. (6) If other derating factors are applied to reduce the conductor ampacity, the conductor size shall be the greater of that so determined or that determined by Subrule (4) or (5). (7) Notwithstanding the requirements of Rule 4-004(1)(d) and (2)(d), the ampacity of the underground conductors shall not exceed in any case those determined by Subrules (4)(b) and (5)(b) of this Rule. - - - Updated - - - Yes. It is the charging current that is fixed while the voltage can vary. Since Power (watts) = Volts * Amps, the resulting power delivered to the car can vary. One problem is that the voltage can vary throughout the day based on a number of factors. Not a lot, maybe 5% but that would affect the power that one user might see compared to another.

I agree completely. It's just that there are those ever so rare circuit breakers, like in Tesla Superchargers, that are rated for 100% continuous current. I'm guessing that they have a current shunt inside and are doing some more sophisticated triggering based on some processing of the monitored current. Here is the appropriate section from the U.S. 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). (A) Continuous and Noncontinuous Loads. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125 percent of the continuous load. Exception: Where the assembly, including the overcurrent devices protecting the branch circuit( s), is listed for operation at 100 percent of its rating, the ampere rating of the overcurrent device shall be permitted to be not less than the sum of the continuous load plus the noncontinuous load. National Electrical Code® (NEC®), 2014 Edition (National Fire Protection Associations National Electrical Code

Maybe when you use a J1772 plugshare location, and you have dual onboard chargers.. see what you can pull out of the station and put your observed / actual current draw as a comment on plugshare for that location. Maximum will be 80.