EV Charging and KNX: Easee Equalizer OCPP, Dynamic Load Management and SG Ready
Integrating EV chargers with KNX building automation via OCPP enables PV surplus-driven dynamic current management — automatically increasing charge rate during solar export and reducing it when the building supply approaches its fuse limit, preventing costly supply upgrades while maximising self-consumption.
EU EV charging mandate and KNX DLM requirement
European regulation is driving mandatory EV charging provision across new and refurbished buildings, with dynamic load management (DLM) increasingly required to protect existing LV supply infrastructure. KNX building automation is well-positioned to provide the DLM control signal.
EU AFIR and EPBD mandates
- EU Regulation 2023/1804 (AFIR): EV charging infrastructure mandated at commercial car parks from 2025 — minimum 1 charger per 10 spaces for buildings >5 spaces
- EU EPBD 2024 revision: EV-ready conduit infrastructure mandatory for new residential buildings with parking, active charging for non-residential from 2027
- UK PAS 1899:2022: EV charging standard requiring active load management and smart charging capability for installations above 7.4 kW total
BREEAM Tra 03 EV credit
- Provide EV charging for ≥ 10% of car park spaces: 1 credit
- EV charging for ≥ 40% of spaces: additional credit (Outstanding)
- Active DLM required for full credit — passive provision scores less
- BREEAM assessor evidence: OCPP installation certificate, DLM capability demonstration, BMS connectivity (KNX integration satisfies BMS requirement)
Easee Home and Easee Charge: hardware overview
Easee is a Norwegian EV charger manufacturer whose products implement OCPP 1.6J natively, making them straightforward to integrate with any OCPP-compatible charge point management system (CPMS) or open-source client such as EVCC.
| Model | Power | Phases | OCPP | Notes |
|---|---|---|---|---|
| Easee Home | 7.4 kW | 1-phase | OCPP 1.6J | 23mm DIN-rail, Wi-Fi + Bluetooth, Type 2 socket, indoor/outdoor IP54 |
| Easee Charge | 22 kW | 3-phase | OCPP 1.6J | 3-phase 32A, Type 2 socket, commercial car parks, networked |
| Easee Equalizer | — | 3-phase | — | Separate DIN-rail current sensor unit — measures L1/L2/L3 building current and auto-limits Easee chargers via Easee cloud |
Easee Equalizer vs KNX DLM: the Easee Equalizer provides standalone DLM without KNX — it measures building main supply current and automatically reduces EV charge current to prevent overload. However, it has no awareness of PV surplus. Adding KNX integration via EVCC gives the system PV surplus data from the Fronius Modbus gateway, enabling active current increase during solar export hours — which the Equalizer alone cannot provide.
OCPP to KNX integration via EVCC
OCPP (Open Charge Point Protocol) version 1.6J operates over WebSocket — either to the Easee cloud or to a local CPMS. The most practical open-source integration path for KNX buildings uses EVCC (EV Charge Controller) running on a local server, connecting to both the Easee charger (OCPP) and the Fronius inverter (Modbus TCP), then publishing state to Home Assistant which forwards control signals to KNX.
Integration architecture
Fronius inverter (Modbus TCP) ──────────┐
├──→ EVCC (local server)
Easee charger (OCPP 1.6J WebSocket) ───┘ │
↓
Home Assistant (EVCC add-on)
│
HA KNX integration (XKNX library)
│
KNX TP bus → GA for EV current limit
Hardware options for EVCC server:
Raspberry Pi 4 (4GB): EVCC + Home Assistant OS (recommended)
Synology NAS: Docker container (EVCC Docker image)
Home Assistant Green: ready-made HA hardware with EVCC add-on
EVCC configuration (evcc.yaml):
chargers:
- name: easee_home
type: easee
user: <Easee app email>
password: <Easee app password>
meters:
- name: fronius_pv
type: fronius
uri: http://<fronius-ip>Dynamic load management: current control logic
With EVCC connected to both the Fronius inverter and the Easee charger, dynamic current adjustment responds to PV surplus in near-real-time. The Fronius grid power register (GA 9/0/1 in KNX) drives current increase and decrease decisions.
DLM control loop (EVCC / KNX logic)
Poll cycle: every 30 seconds
If GA 9/0/1 (Grid Power) < −2000W (export surplus > 2 kW):
→ Calculate new EV current:
current_A = surplus_W ÷ 230 (single phase, Easee Home)
→ Clamp to range [6A, 16A] (OCPP standard limits)
→ Send OCPP ChangeConfiguration: maxChargingCurrent = current_A
If GA 9/0/1 > −500W (surplus dropped below 500W):
→ Reduce EV current to minimum: 6A
→ Wait 60 seconds before next increase (hysteresis)
If GA 9/0/1 > +500W (building importing > 500W):
→ Reduce EV current toward minimum (supply shortage)
→ Easee Equalizer simultaneously limits via hardware DLM
Note: minimum OCPP current is 6A (1.38kW single phase)
If PV surplus < 1.4kW → suspend EV charging entirely
Resume when surplus exceeds 1.4kW for 2 consecutive minutesCharging current formula
Converting PV surplus power to OCPP current setpoint requires knowing whether the charger is single-phase or 3-phase. The formula is different for each configuration.
Current setpoint calculation
Single-phase (Easee Home, 230V): current_A = surplus_W ÷ 230 Example: surplus 3680W → 3680 ÷ 230 = 16A (maximum for 7.4kW) Example: surplus 1840W → 1840 ÷ 230 = 8A 3-phase (Easee Charge, 400V): current_A = surplus_W ÷ (√3 × 400) = surplus_W ÷ 692 Example: surplus 13840W → 13840 ÷ 692 = 20A Example: surplus 4152W → 4152 ÷ 692 = 6A (minimum 3-phase) OCPP current limits: Minimum: 6A (below this, most EVs stop accepting charge) Maximum single-phase: 16A (Easee Home 7.4kW) Maximum 3-phase: 32A (Easee Charge 22kW) Vehicle acceptance: some EVs (older Renault Zoe, early Nissan Leaf) require minimum 8A or 10A — configure EVCC minimum accordingly
Phase imbalance consideration: a single-phase EV charger drawing 16A on L1 creates 16A imbalance on a 3-phase supply. In buildings with a 3-phase main supply, Easee Equalizer monitors all three phases independently and limits per-phase current — preventing neutral overload from single-phase EV chargers while allowing other phases to carry their full load.
Wallbox Pulsar Plus: alternative charger
The Wallbox Pulsar Plus is a frequently specified alternative to Easee, offering OCPP 1.6J over Wi-Fi and the same EVCC integration path. Wallbox Power Boost (a separate clip-on current sensor) provides hardware DLM equivalent to the Easee Equalizer.
Wallbox Pulsar Plus
- 7.4 kW single-phase or 22 kW 3-phase
- OCPP 1.6J over Wi-Fi (cloud or local)
- EVCC supported charger (wallbox type)
- Mybox app for local configuration
- IP54, compact wall-mount design
Wallbox Power Boost
- Clip-on CT sensor on main supply cables
- Communicates with Pulsar Plus via Wi-Fi
- Hardware DLM without needing KNX signal
- No integration with PV inverter (supply protection only)
- Use alongside EVCC for full PV + DLM control
Simple KNX binary output for basic EV chargers
For EV chargers without OCPP support, a KNX binary output relay controlling the charger enable input (or a contactor in the charger supply circuit) provides on/off control based on PV surplus. This approach lacks intermediate current adjustment but is simple to implement with any KNX-compatible binary output module.
Binary output relay control logic
Enable condition: GA 9/0/1 (Grid Power) < −1400W (surplus > 1.4kW = 6A minimum) AND GA 9/1/0 (Battery SOC) > 20% → KNX binary output ON → charger enable relay closes → EV charger activates at configured maximum current Disable condition: GA 9/0/1 > −1000W (surplus below 1kW) OR GA 9/1/0 < 15% → KNX binary output OFF → relay opens → charger pauses → 3-minute hysteresis (avoid rapid on/off cycling) Relay specification: KNX binary output: MDT BE-04.01 or ABB SA/S 4.6.2.1 Relay rating: ≥ 16A for 7.4kW charger supply contactor Use contactor for charger supply (not pilot wire) where possible — pilot wire interruption may cause charger errors
OCPP preferred over relay control: the relay approach provides on/off PV management only, whereas OCPP allows 11 intermediate current steps between 6A and 16A single-phase. With OCPP, a 3.5 kW surplus charges the EV at a matching 3.5 kW rather than wasting the surplus to the grid while waiting for the full 7.4 kW threshold. EVCC on a Raspberry Pi (approx. EUR 80 hardware) is a small investment relative to the lifetime value of improved self-consumption.
Combined SG Ready and EV priority logic
When both a heat pump with SG Ready and an EV charger with OCPP are present, the KNX logic controller must allocate PV surplus across both loads intelligently. The following priority table distributes surplus across the available controllable loads.
| PV surplus | EV charge current | SG Ready state | Condition |
|---|---|---|---|
| < 1.4 kW | Suspended (< 6A minimum) | State 2 (normal) | Insufficient for EV minimum current |
| 1–3 kW | 6A (1.38 kW) | State 2 (normal) | EV minimum only — heat pump not triggered |
| 3–6 kW | 10A (2.3 kW) | State 3 (encouraged) | EV increases + heat pump SG Ready activated |
| > 6 kW | 16A (3.68 kW) | State 4 (maximum) | Both loads at maximum; battery charging remaining |
| Any, SOC < 20% | Suspended | State 2 (normal) | Battery priority — suspend EV, normal heat pump |
MDT Logic Module nested condition implementation
Logic channel 1: Battery low guard IF GA 9/1/0 (SOC) < 20% → set internal flag "battery_priority" Logic channel 2: EV enable IF GA 9/0/1 < −1400W AND NOT battery_priority → GA for EVCC current setpoint = surplus_W ÷ 230 Logic channel 3: SG Ready State 3 trigger IF GA 9/0/1 < −3000W AND NOT battery_priority → SG Ready S2 output ON (State 3) Logic channel 4: SG Ready State 4 trigger IF GA 9/0/1 < −6000W AND NOT battery_priority → SG Ready S1 AND S2 output ON (State 4) Logic channel 5: Battery priority release IF GA 9/1/0 > 30% → clear battery_priority flag
BREEAM Tra 03 compliance documentation
BREEAM Transport credit Tra 03 awards credits for EV charging provision, with additional weight for active dynamic load control demonstrating building management system integration. The following documentation package satisfies BREEAM assessor evidence requirements.
BREEAM Tra 03 evidence package
Required documentation for BREEAM assessor: 1. EV charging provision schedule: Table: space number, charger model, power (kW), OCPP version Confirm: ≥10% of spaces (Excellent) or ≥40% (Outstanding) 2. OCPP installation certificate: Easee commissioning report showing OCPP 1.6J enabled EVCC connection log showing charger status: Connected 3. Dynamic load management evidence: EVCC configuration showing max_current adaptive mode Fronius Modbus integration configured (grid power input) Screenshot: EVCC dashboard showing current varying with PV 4. BMS connectivity evidence: KNX ETS6 project extract showing GA for EV current limit EVCC → Home Assistant → KNX integration configuration ETS6 Group Monitor log: GA updates as PV surplus changes 5. Commissioning test record: Date, engineer name, test steps and measured results (per commissioning test sequence below)
Commissioning test sequence
The commissioning test sequence verifies every element of the integration chain — from OCPP connectivity through to KNX group address updates — and produces the test record required for BREEAM assessor evidence.
Five-step commissioning verification
Step 1 — OCPP connectivity: Open EVCC web UI → Loadpoints Plug EV (or OCPP test plug) into Easee charger Confirm status: Connected / Charging EVCC logs: [INFO] easee: connected via OCPP 1.6J Step 2 — Manual current limit test: Set EVCC minimum current: 6A Confirm EV accepts charge at 6A Verify in Easee app: Charging at 6A / 1.4kW Increase EVCC limit to 16A → confirm Easee app shows 16A Step 3 — PV surplus test (on a sunny day): On a day with clear sky and EV connected: Observe EVCC dashboard — current should increase as Fronius GA 9/0/1 drops (more surplus) Log: initial current 6A → 10A by 11:00 → 16A by 12:30 Step 4 — DLM test (Equalizer overload protection): Switch on major resistive loads (electric heaters) Until main supply L1 current approaches fuse rating (63A) Verify: Easee Equalizer reduces EV current automatically Confirm in Easee app: current reduction event visible Step 5 — KNX verification: ETS6 Group Monitor — monitor GA for EV current limit Confirm GA value updates as EVCC changes current setpoint Record: timestamp, surplus power, OCPP current, GA value → Provide as BMS connectivity evidence for BREEAM
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