This article is intended to provide guidance as to how to wire a ZEFNET EVSE into an external load controller.
External Load Controller
Materials Provided with EVSE:
Hardwired ZEFNET EVSE
Installation - Prerequisites
This article assumes you have followed the ZEFNET Installation wiring guide, so that the high voltage wire-in is complete. See this article for more information:
This article also assumes that the load controller has already been installed, and only requires connecting the control relay to the load to be controlled (in this case, the ZEFNET charger). If an external load controller will not be used immediately, it is strongly recommended that the control whip is terminated into a junction box adjacent to the ZEFNE TEVSE.
Note: The external load control methodology used on the ZEFNET charger does not require a large contactor or high capacity relay, and will not interrupt power to the communication systems internal to the charger.
Installation - Low Voltage Load Management Wiring
Firstly, you will want to determine whether to use a NC or NO relay. The control line on the ZEFNET charger will interrupt power when continuity is achieved across the two wires. Your organisation and specific program will determine which relay to use, depending on the end user program.
Example: if your load controller engages between 6am and 11pm in order to curtail usage during the day, you will require a NO relay. When engaged, continuity will be observed across the two wires and the ZEFNET EVSE will shed the load.
Illustrated below is the ZEFNET EVSE, with both the Power and Load Control whips exiting the bottom of the enclosure.
The Load Control whip consists of multiple different color wires (between 4 and 8). It is the blue and green wires we are primarily concerned with:
Typically a 5 amp control relay is placed between the green and blue signal wires. When engaged with one another, the ZEFNET charger shall shed the load, in a similar way to an air conditioner or ASHP. The ZEFNET EVSE is still powered and communications from the unit will still continue back to the ZEFNET cloud. The advantage of this methodology is that the installation is significantly more cost effective than installing a high power contactor external enclosure, and both organizations and consumers can still have a window into the operation of their charger through either the web or mobile app.
Optionally, utilities can allow residential charger users the ability to override a curtailment (this is an option when creating the load control event/schedule in the ZEFNET headend software). A utility may want to do this to provide the most amount of flexibility to the residential program user, where an occasional override of the load control signal is required to allow the driver to get the charge they need. This can help keep drivers stay on the program, stemming program attrition. This function can be enabled or disabled at any time, and does not require a site visit or any physical or electrical changes to the installation.