# Boiler Auxiliary Heater Control

A Home Assistant custom integration for intelligently controlling an auxiliary electric heating element inside a DHW (Domestic Hot Water) boiler. Designed for systems where a heat pump is the primary heat source and an electric resistance heater is the secondary element.

The integration maximises PV self-consumption by diverting surplus solar energy to the boiler, while also supporting on-demand bath boost heating and fully configurable temperature presets.

---

## Features

- **PV Excess Diversion** — monitors up to 3 CT clamps (single-phase or 3-phase) and activates the heater only when there is enough surplus export, using configurable start/stop delays to avoid rapid cycling
- **Bath Boost** — one-tap hot water on demand; activates the heater and optionally runs the DHW circulation pump for a configurable duration, then automatically restores the previous state
- **5 Temperature Presets** — Normal, Eco, Boost, Sleep, Away, each with individually adjustable target temperatures
- **All-Modes Boost** — optional mode that lets the aux heater top up the boiler whenever the thermostat demands heat, regardless of PV availability
- **Safety Interlocks** — hard cut-off temperature, HP aux heater interlock (disables aux heater while the heat pump's own electric element is running), and safe defaults for unavailable sensors
- **Energy Tracking** — separate kWh counters for total, PV-sourced, and grid-sourced energy, compatible with HA's Energy Dashboard
- **Decision Transparency** — a `Decision Reason` sensor tells you exactly why the heater is on or off at any moment
- **Persistent State** — all settings and an active bath boost survive HA restarts
- **Ready-to-Use Dashboard** — an importable Lovelace dashboard is included

---

## Requirements

- Home Assistant 2024.1.0 or newer
- A temperature sensor measuring the boiler water temperature (device class: `temperature`)
- A switch entity controlling the heater relay
- One or more power sensors measuring grid import/export at each phase (device class: `power`, **negative = export**)

Optional:
- A binary sensor indicating whether the heat pump's own auxiliary heater is active (for interlock)
- A switch entity for a DHW circulation pump (enables the bath boost button)
- A scheduler entity for the pump (its schedule is restored after bath boost)

---

## Installation

### Via HACS (recommended)

1. Open HACS in Home Assistant
2. Go to **Integrations** → click the three-dot menu → **Custom repositories**
3. Add this repository URL and select category **Integration**
4. Search for **Boiler Auxiliary Heater Control** and install
5. Restart Home Assistant

### Manual

1. Copy the `custom_components/boiler_aux_heater_3phase` folder into your HA `config/custom_components/` directory
2. Restart Home Assistant

---

## Configuration

Navigate to **Settings → Devices & Services → Add Integration** and search for **Boiler Auxiliary Heater Control**.

The setup wizard has three steps:

### Step 1 — Core Hardware

| Field | Description |
|-------|-------------|
| Boiler temperature sensor | Sensor measuring the DHW tank temperature (must have device class `temperature`) |
| Heater relay switch | The switch entity that controls the heating element |

### Step 2 — Solar Monitoring

| Field | Description |
|-------|-------------|
| Number of phases | `1 Phase` or `3 Phases` |
| Phase 1 CT power sensor | Grid power sensor for phase 1 (negative = exporting) |
| Phase 2 CT power sensor | Phase 2 sensor (3-phase only, optional) |
| Phase 3 CT power sensor | Phase 3 sensor (3-phase only, optional) |

> **Important:** the CT sensors must report **negative values for export** and positive values for import. This is the convention used by most inverter integrations (Fronius, SolarEdge, Huawei, etc.).

### Step 3 — Optional Devices

| Field | Description |
|-------|-------------|
| HP aux heater sensor | Binary sensor that is `on` when the heat pump's own electric element is active. If provided, the aux heater is disabled while this sensor is `on`. If the sensor becomes **unavailable**, the aux heater is disabled as a safety measure. |
| Circulation pump switch | Switch controlling a DHW circulation pump. When provided, the **Bath Boost** button entities are created. |
| Pump schedule entity | A scheduler entity whose schedule is re-applied after bath boost finishes. |

After initial setup, all entity references can be changed via **Configure** on the integration card.

---

## Entities

### Climate

| Entity | Description |
|--------|-------------|
| `climate.boiler_auxiliary_heater` | Main thermostat. Set HVAC mode (`heat`/`off`) and choose a preset. |

**Presets:** Normal · Eco · Boost · Sleep · Away

Selecting the **Boost** preset starts the bath boost timer. Selecting any other preset while boost is active cancels the boost.

---

### Switches (Configuration)

| Entity | Default | Description |
|--------|---------|-------------|
| `switch…allow_aux_heater_usage` | ON | Master enable. Turn off to disable the aux heater entirely. |
| `switch…pv_excess_mode` | ON | Enable PV excess diversion. |
| `switch…boost_in_all_modes` | OFF | Allow the heater to run whenever the thermostat demands heat, regardless of PV. Uses the larger all-modes hysteresis to avoid short cycling. |
| `switch…manual_override` | OFF | Force the relay ON, bypassing all logic. For testing or emergencies only. |

---

### Numbers (Configuration)

**Temperatures**

| Entity | Default | Range | Description |
|--------|---------|-------|-------------|
| `number…cut_off_temperature` | 60 °C | 40–85 | Hard safety limit. Heater is always off above this temperature. |
| `number…temperature_hysteresis` | 4 °C | 1–15 | How far below the target temperature heating must be demanded before activating. Also used as PV shadow thermostat cold tolerance. |
| `number…pv_target_temperature` | 55 °C | 40–70 | Target temperature for PV excess mode. Max is automatically capped at `cut_off_temp - 1`. |
| `number…normal_preset_temperature` | 44 °C | 30–65 | Target for Normal preset. |
| `number…eco_preset_temperature` | 40 °C | 30–60 | Target for Eco preset. |
| `number…boost_preset_temperature` | 50 °C | 40–70 | Target for Boost preset. |
| `number…sleep_preset_temperature` | 38 °C | 25–55 | Target for Sleep preset. |
| `number…away_preset_temperature` | 35 °C | 20–50 | Target for Away preset. |

**PV Excess Settings**

| Entity | Default | Range | Description |
|--------|---------|-------|-------------|
| `number…heater_power_rating` | 4500 W | 1500–9000 | Rated wattage of the heating element. Used for PV surplus threshold and energy calculations. |
| `number…pv_excess_buffer` | 100 W | 0–1000 | Additional margin required above heater power before PV mode activates. Prevents marginal activation. |
| `number…pv_excess_start_delay` | 60 s | 1–300 | How long PV surplus must be sustained before activating. Prevents cloud transients from triggering the heater. |
| `number…pv_excess_stop_delay` | 60 s | 1–300 | How long PV deficit must be sustained before deactivating. Allows short shading events without turning off. |

**Bath Boost & All-Modes Settings**

| Entity | Default | Range | Description |
|--------|---------|-------|-------------|
| `number…bath_boost_duration` | 30 min | 5–120 | How long bath boost runs. |
| `number…all_modes_boost_hysteresis` | 10 °C | 3–20 | Temperature must be this far below target for all-modes boost to activate. Larger value → heater activates less often. |
| `number…boost_recovery_offset` | 3 °C | 0–15 | All-modes boost turns off when temperature reaches `target - boost_recovery_offset`. |

---

### Binary Sensors (Status)

| Entity | Description |
|--------|-------------|
| `binary_sensor…heater_decision` | `on` = heater relay should be on right now. |
| `binary_sensor…pv_power_sufficient` | `on` = current PV export is enough to run the heater. |
| `binary_sensor…running_on_pv` | `on` = heater is running and powered by PV surplus. |
| `binary_sensor…running_on_grid` | `on` = heater is running on grid power (bath boost or all-modes boost). |
| `binary_sensor…bath_boost_active` | `on` = bath boost timer is running. |

---

### Sensors (Status)

| Entity | Description |
|--------|-------------|
| `sensor…heater_power` | Current total power consumption of the heater (W). |
| `sensor…heater_pv_power` | Current power drawn from PV surplus (W). |
| `sensor…heater_grid_power` | Current power drawn from the grid (W). |
| `sensor…heater_energy` | Total energy consumed (kWh) — suitable for HA Energy Dashboard. |
| `sensor…heater_pv_energy` | Energy consumed from PV (kWh). |
| `sensor…heater_grid_energy` | Energy consumed from grid (kWh). |
| `sensor…bath_boost_remaining` | Seconds remaining in the current bath boost (0 when inactive). |
| `sensor…decision_reason` | Human-readable text explaining the current heater decision, e.g. *"PV excess heating"* or *"OFF: HP aux heater active"*. |
| `sensor…pv_excess_state` | PV state machine state: `idle`, `waiting_to_start`, `active`, or `waiting_to_stop`. |

---

### Buttons (optional — only if circulation pump is configured)

| Entity | Description |
|--------|-------------|
| `button…start_bath_boost` | Start the bath boost timer immediately. |
| `button…cancel_bath_boost` | Cancel an active bath boost and restore previous state. |

---

## Services

Both services are always available, regardless of whether a circulation pump is configured.

### `boiler_aux_heater_3phase.start_bath_boost`

Starts the bath boost. Saves the current climate preset, activates the Boost preset, starts the countdown timer, and (if configured) turns on the circulation pump.

```yaml
service: boiler_aux_heater_3phase.start_bath_boost
```

### `boiler_aux_heater_3phase.stop_bath_boost`

Cancels an active bath boost, restores the previous preset, and (if configured) turns off the circulation pump and re-applies the pump schedule.

```yaml
service: boiler_aux_heater_3phase.stop_bath_boost
```

---

## Events

When a bath boost expires naturally (timer runs out), the integration fires:

```
event: boiler_aux_heater_3phase_boost_finished
data:
  duration_minutes: 30
  pre_boost_preset: "Normal"
  restored_preset: "Normal"
```

You can use this event in automations to notify occupants or take further action.

---

## How the PV Excess Logic Works

```
For each active CT phase:
  Turn-on threshold:  CT_value < -(heater_power / phases + pv_buffer / phases)
  Stay-on threshold:  CT_value <= 0   (any export at all)

State machine:
  IDLE  ──[all phases meet turn-on threshold]──►  WAITING_TO_START
  WAITING_TO_START  ──[pv_start_delay elapsed]──►  ACTIVE
  WAITING_TO_START  ──[PV drops]──►  IDLE
  ACTIVE  ──[any phase stops exporting]──►  WAITING_TO_STOP
  WAITING_TO_STOP  ──[pv_stop_delay elapsed]──►  IDLE
  WAITING_TO_STOP  ──[PV recovers]──►  ACTIVE
```

While in `ACTIVE` or `WAITING_TO_STOP`, the PV shadow thermostat checks whether the boiler temperature is below `pv_target_temp`. This prevents unnecessarily overheating the tank on very sunny days.

---

## Dashboard

A ready-to-use Lovelace dashboard is included in `custom_components/boiler_aux_heater_3phase/dashboard.yaml`.

To import it:
1. Go to **Settings → Dashboards → Add Dashboard**
2. Or use the **Raw Configuration Editor** in an existing dashboard and paste the YAML

The dashboard includes sections for:
- Thermostat control with preset dropdown
- Bath boost controls and timer
- Mode switches
- Preset temperature configuration
- Safety and heater settings
- PV excess settings
- Live status (decision, PV state, power & energy)

---

## Automation Examples

### Notify when bath boost finishes

```yaml
automation:
  - alias: "Notify bath boost done"
    trigger:
      - platform: event
        event_type: boiler_aux_heater_3phase_boost_finished
    action:
      - service: notify.mobile_app_my_phone
        data:
          message: "Hot water ready! Tank heated for {{ trigger.event.data.duration_minutes }} minutes."
```

### Switch to Away preset when leaving home

```yaml
automation:
  - alias: "Boiler away mode"
    trigger:
      - platform: state
        entity_id: person.resident
        to: not_home
    action:
      - service: climate.set_preset_mode
        target:
          entity_id: climate.boiler_auxiliary_heater
        data:
          preset_mode: Away
```

### Start bath boost on a schedule

```yaml
automation:
  - alias: "Morning bath boost"
    trigger:
      - platform: time
        at: "07:00:00"
    condition:
      - condition: state
        entity_id: binary_sensor.workday_sensor
        state: "on"
    action:
      - service: boiler_aux_heater_3phase.start_bath_boost
```

---

## Troubleshooting

**Heater never activates in PV mode**
- Check `sensor…pv_excess_state` — if it stays `idle`, the CT sensors may not be reporting negative values when exporting. Confirm the sign convention of your inverter integration.
- Check that `switch…pv_excess_mode` is on and `switch…allow_aux_heater_usage` is on.
- Check `sensor…decision_reason` for the exact reason the heater is off.
- Increase `pv_excess_buffer` to 0 temporarily to rule out threshold issues.

**HP aux heater interlock keeps the heater off**
- If the HP aux heater binary sensor reads `unavailable`, the integration disables the aux heater as a safety measure. Check the sensor entity or remove it from the configuration if not needed.

**Bath boost buttons are missing**
- The bath boost buttons are only created when a circulation pump switch is configured. Go to **Configure** on the integration card to add one. The `start_bath_boost` and `stop_bath_boost` services are always available regardless.

**Energy counters reset after restart**
- Energy sensors use `RestoreEntity` to persist their values. If values are lost, check that the HA recorder is running and that the entities are not excluded from recording.

**PV mode activates but heater stays off**
- Check `sensor…decision_reason`. Common causes: boiler temperature above `cut_off_temperature`, HVAC mode set to `off`, or `allow_aux_heater_usage` switch is off.

---

## License

MIT License — see [LICENSE](LICENSE) for details.