Electric vehicle charging infrastructure is among the most technically nuanced additions a building owner can make to an existing electrical installation. The charging standard, the circuit design, the switchboard capacity, and the load management strategy all interact in ways that a simple 'plug in a charger' approach cannot address. Nexus Grid engineers treat every EV charging project as a load-design exercise — calculating available maximum demand headroom under AS/NZS 3000:2018, specifying compliant supply equipment to AS/NZS 61851, and selecting hardware with the OCPP integration capability to manage energy cost and grid impact over the life of the installation.
AS/NZS 61851 Modes and Supply Equipment Classification
AS/NZS 61851 — the Australian adoption of IEC 61851 — classifies EV supply equipment (EVSE) into four modes. Mode 1 (standard socket outlet, no pilot signal) is prohibited for new EV charging installations in Australia. Mode 2 (portable EVSE with in-cable control box) is limited to temporary or domestic-emergency use. Mode 3 — a dedicated AC supply with a fixed EVSE, pilot signal communication between the vehicle and the station, and a Type 2 connector complying with IEC 62196 — is the required mode for all new permanent installations, residential or commercial. Mode 4 covers DC fast charging at 50 kW and above, which requires specialised switchboard infeed and earthing arrangements beyond the scope of typical site power.
A Mode 3 single-phase charger operating at 32A delivers 7.36 kW — sufficient to add approximately 40–50 km of range per hour for a typical battery-electric passenger vehicle. A three-phase Mode 3 charger at 32A per phase delivers up to 22 kW, adding 100–120 km of range per hour and reducing overnight fleet dwell-time requirements significantly. The choice between single-phase and three-phase supply depends on vehicle on-board charger capability, available site supply, and switchboard capacity.
Dedicated Circuit Design and Switchboard Assessment
AS/NZS 61851 and AS/NZS 3000:2018 both require EV chargers to be supplied from a dedicated final sub-circuit — not shared with other loads. For a 7 kW single-phase unit, the circuit requires a 32A Type C MCB, 6mm² copper TPS conductors to manage voltage drop over longer cable runs, a dedicated 30mA RCD, and an earthing conductor sized per AS/NZS 3000 Table 5.1. For a 22 kW three-phase installation, a dedicated 3-phase 32A circuit is required, with conductor sizing recalculated against AS/NZS 3008.1.1 for the actual cable route length.
Before specifying any hardware, Nexus Grid engineers assess the existing switchboard for available maximum demand headroom using the calculation method in AS/NZS 3000 Section 2. Adding one 22 kW three-phase charger to a commercial premises already operating near its agreed capacity limit can trigger a distribution network service provider (DNSP) network connection application and potentially require transformer augmentation — costs that can dwarf the charger hardware and installation combined. Identifying this risk upfront and designing around it with load management is central to our engineering approach.
Load Management, Dynamic Power Sharing and OCPP
Where multiple chargers are installed, or where the site supply headroom is constrained, dynamic load management is the engineering solution that avoids costly supply upgrades. Nexus Grid designs load-managed charging systems using a site controller that monitors the main incomer current via CT sensors and signals each OCPP-compliant charger to throttle output in real time. Under AS/NZS 61851, EVSE must respond to a pilot-signal reduction by reducing charge current within a specified response time — OCPP 1.6 and 2.0 protocols extend this control to the network level, enabling managed charging, scheduled off-peak sessions, and integration with solar PV generation curves.
- Mode 3 EVSE complying with AS/NZS 61851, IEC 62196 Type 2 connector, pilot-signal communication
- Dedicated 32A final sub-circuit per charger — no shared circuits per AS/NZS 3000:2018
- Switchboard maximum demand assessment before specifying charge power level
- Dynamic load management via CT-monitored site controller and OCPP 1.6/2.0 protocol
- Single-phase 7 kW or three-phase 22 kW supply based on vehicle fleet and switchboard capacity
- 30mA RCD protection and Type C MCB on every EV charging circuit
- DNSP connection notification or application prepared where required by network rules
Commercial and Multi-Bay Installations
Commercial carparks, strata buildings, and fleet depots require a structured charging infrastructure plan rather than ad hoc unit additions. Nexus Grid prepares a site master plan that identifies primary cable routes, switchboard augmentation requirements, and the number of active and passive (conduit-ready) bays required for staged roll-out. Where strata or body corporate arrangements apply, our engineers prepare technical reports suitable for owners' corporation approval, including maximum demand impact assessments and proposed metering arrangements for billing individual tenants or residents for energy consumed. All installations are completed with AS/NZS 3017 test records and a commissioning checklist validating OCPP cloud connectivity before handover.