Robert, I have no clue why you continue to insist that a 20A breaker with a 20A NEMA outlet is an unsafe situation - this is standard practice in every single home and business in the USA, so if it were unsafe then the NEC and building code would not have allowed it. Also, it is the job of the user of the system to take care not to plug too much load in, since many outlets may be daisy-chained on a single 20A service (breaker + wiring) and if too much load is plugged in, then the breaker will protect the service from overload. Even that is daily practice. Installing an identical system (20A breakers or even 15A breakers if you want to minimize the aggregate max current draw) in an outdoor system is not much different, other than using weather-protected GFCI outlets.
Your other beef is with the use of a 50A capable circuit (whether it is an EVSE or just a straight run of #6 wire does not matter) that gets "converted" to a 20A capable outlet (you call that adapter). The safe way of doing that is to include a 20A breaker in the converter so that even while it is on a 50A capable circuit, you can only draw 20A from the 20A outlet before the breaker blows, protecting the wiring (and outlet). Hope this helps, Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626 Skype: cor_van_de_water XoIP +31 87 784 1130 private: cvandewater.info http://www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of ROBERT via EV Sent: Tuesday, November 08, 2016 10:32 PM To: Roger Stockton; Electric Vehicle Discussion List Subject: Re: [EVDL] CheapL2 charging in parking places: Bolt EV'sIn Production Roger, let me try to clarify my concern. A person buys a third party J1772 to NEMA adapter (made in China and made cheap). The adapter has a NEMA rated 20A plug. The adapter does not produce a modified pilot signal. I take the cord and plug from the EVSE that is rated at 50A and plug into the adapter. I take the 20A coil and plug from the charger in my converted car and plug into the adapter. The charger will not draw more than 20A from the EVSE. This is OK load wise because the EVSE can output 50A. However, it is an unsafe circuit. I have connected a 50A rated source to a 20A circuit with no interconnecting protection device. This is no different than connecting a 12AWG wire to a 50A breaker. Lets go the other direction. I have a NEMA to J1772 adapter with no pilot signal. If the cable from the adapter is plugged into a car with a 50A charger, the circuit breaker will trip (you described this situation in your email). This is an unsafe operation. A circuit bre aker is designed to protect the cable not the end load. You can check the NEC to verify this is a true statement. Circuit breaker are not used for end load protection. The end load device must have its own protection. If I have a large scale NEMA receptacle system, I cannot prevent people from using "bad equipment" or "bad configurations of equipment". If I use a EVSE system with approved equipment, these unsafe situations are minimized. This was my point when I made this statement concerning unsafe adapters and a large size NEMA plug installation. ________________________________ From: EV <[email protected]> on behalf of Roger Stockton via EV <[email protected]> Sent: Tuesday, November 8, 2016 5:36 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Cheap L2 charging in parking places: Bolt EV'sIn Production ROBERT via EV wrote: > Again I must correct myself. I looked back at the J1772 standard and some > past work that I did. An EVSE outputs a 1KHz square wave. The duty cycle > of this wave informs the the vehicle of the maximum amperage that the EVSE > can supply (rated current). The vehicle is responsible for not drawings a > current greater than the EVSE rating. Yes. > All lower amperage adapters must > limit this duty cycle to the rating of the adapter. As an example. If > the EVSE is rated at 50 amps and the adapter is only rated for 20A, the > adapter must adjust the duty cycle. This is where you lose me. If the EVSE is rated for 50A, then it generates a pilot signal that informs the vehicle/charger that it can draw up to this amount. There is no need or purpose for an adapter between the EVSE and a vehicle unless the vehicle does not have a J1772 inlet. If the vehicle doesn't have a J1772 inlet, then it also doesn't need (or understand) the J1772 pilot signal and so there is no need for an adapter to generate a pilot signal limiting the vehicle to a lower current than the EVSE is capable of providing. > It is possible to design a 20A > adapter with a switch and a resistor that does not modify the duty cycle > from the EVSE. Yes, and this adapter is used to convert a J1772 EVSE *into* a NEMA receptacle so that a non-J1772 compliant EV/charger may be plugged into a public charging station. This is exactly the opposite of what would be required or used if NEMA receptacles were provided at each charging stall. Most of us with conversion EVs have chargers that can plug directly into a NEMA outlet, and would not need an adapter more sophisticated than an extension cord. Those of us with production EVs (other than Teslas, perhaps) will have J1772 inlets and will need to use our J1772 "opportunity charge" cords; these are effectively "smart" extension cords with a NEMA plug on the wall end, a J1772 charge paddle on the vehicle end, and a small EVSE in between that provides the appropriate pilot signal for the vehicle/charger. If the NEMA plug on the wall end of the opportunity charge cord is a NEMA 5-15P, then the pilot signal should (must!) tell the charger not to draw more than 12A. If the cord has a NEMA 5-20P plug, then the pilot signal can allow the charger to draw up to 16A (since this plug can only mate with a receptacle on a 20A rated circuit). Even if the J1772 opportunity charge cord were to tell the charger it is OK to draw more current than the NEMA receptacle and circuit are rated for, there should be no safety issue: the NEMA receptacle and its associated supply wiring will be protected by an appropriately rated breaker and the breaker will simply open. Cheers, Roger. _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org EV -- Electric Vehicle Discussion List - lists.evdl.org ...<http://lists.evdl.org/listinfo.cgi/ev-evdl.org> lists.evdl.org The Electric Vehicle Discussion List is a forum for discussing the current state of the art and future direction of electric vehicles (EVs). We define an EV as a ... 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