Elephanthead: Tempting as it is to use the Versicharge (dialed down to 1/2 maximum 30a current) on a 20a circuit, the instructions (and so probably the UL listing requirements) do not allow it. From the "Installation and Operations Manual" (Document Number: 813540 [no version/date]):
A -- VersiCharge electric vehicle charging stations can draw up to 30 A at 240 VAC, 60 Hz (7.2kW of power). The complete electrical structure of the building must be adequately sized to handle the entire building energy load, under peak conditions, as well as the charging station load under operation.
B -- Verify that the 30 A draw from the VersiCharge will not exceed the loading for the Main Breaker of the structure.
C -- A 2-pole, 40 A dedicated branch breaker is required for both cord-and-plug installation and hard wired installations.
D -- Circuit must be sized for the max amperage requirement. Do not de-rate breakers or conductors based on amperage adjustment.
E -- The Siemens VersiCharge has the option of reducing the output amperage, to allow installers to define the power output of the device. This is designed to help installers and users manage installation costs and the amount of retrofitting required to install the VersiCharge.
F -- Amperage adjustment dial is for use by a qualified technician only.
G -- Purpose of the amperage adjustment switch is to limit the max power that can be delivered by the charging station.
H -- To provide additional protection, Siemens recommends the use of GFCI circuit breakers. Though this is not required by code, this will provide an additional level of protection for users and their property.
So the circuit must able to handle 40a, which implies at least 8/2 AWG w/ ground, protected by a 40a circuit breaker.
So what is the value of the current limiting feature? One might be that although you have a Leaf with a 6.6kW on-board charger, at home you mainly charge at night and have a full 7 or 8 hours period of time (say, 11:00p to 7:00a) to recharge and for some reason to need to or choose to limit the current demand. As example, perhaps you currently only have 100a (or less) service, and household load calculations indicate it is sufficient for 1/2 (or 3/4) maximum current VersiCharge operation, but not 30a. Or perhaps you have 200a service, but have two (or more) Leafs and a VersiCharge for each -- and again need to or choose to limit the current demand.
A -- VersiCharge electric vehicle charging stations can draw up to 30 A at 240 VAC, 60 Hz (7.2kW of power). The complete electrical structure of the building must be adequately sized to handle the entire building energy load, under peak conditions, as well as the charging station load under operation.
B -- Verify that the 30 A draw from the VersiCharge will not exceed the loading for the Main Breaker of the structure.
C -- A 2-pole, 40 A dedicated branch breaker is required for both cord-and-plug installation and hard wired installations.
D -- Circuit must be sized for the max amperage requirement. Do not de-rate breakers or conductors based on amperage adjustment.
E -- The Siemens VersiCharge has the option of reducing the output amperage, to allow installers to define the power output of the device. This is designed to help installers and users manage installation costs and the amount of retrofitting required to install the VersiCharge.
F -- Amperage adjustment dial is for use by a qualified technician only.
G -- Purpose of the amperage adjustment switch is to limit the max power that can be delivered by the charging station.
H -- To provide additional protection, Siemens recommends the use of GFCI circuit breakers. Though this is not required by code, this will provide an additional level of protection for users and their property.
So the circuit must able to handle 40a, which implies at least 8/2 AWG w/ ground, protected by a 40a circuit breaker.
So what is the value of the current limiting feature? One might be that although you have a Leaf with a 6.6kW on-board charger, at home you mainly charge at night and have a full 7 or 8 hours period of time (say, 11:00p to 7:00a) to recharge and for some reason to need to or choose to limit the current demand. As example, perhaps you currently only have 100a (or less) service, and household load calculations indicate it is sufficient for 1/2 (or 3/4) maximum current VersiCharge operation, but not 30a. Or perhaps you have 200a service, but have two (or more) Leafs and a VersiCharge for each -- and again need to or choose to limit the current demand.