> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ariscomfort.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Get HCU status

> Returns current hydronic control unit status including mode, temperatures, and efficiency.



## OpenAPI

````yaml get /api/hcu
openapi: 3.1.0
info:
  title: Aris API
  version: 1.0.0
  description: >
    REST API for controlling Aris home comfort systems.


    Aris is an air-to-water heat pump system that heats, cools, and provides hot
    water for homes.

    The Aris Brain is the central controller, managing zones, fan-coil units
    (FCUs), heat pumps,

    domestic hot water (DHW), and thermal energy storage (TES).


    ## Base URL


    The Aris Brain runs on your local network. Find your Brain's address via:

    - mDNS: `http://aris.local` (if your network supports mDNS)

    - Router admin panel: Look for a device named "aris-brain"


    ## Authentication


    Most API endpoints require authentication via Bearer token. Create an API
    token in the Aris web UI under **Settings → API Tokens**.


    Include the token in the `Authorization` header:

    ```

    Authorization: Bearer your-api-token

    ```


    ## Real-time Updates


    For real-time updates, connect to the WebSocket at
    `ws://aris.local?token=YOUR_API_TOKEN`.

    The WebSocket broadcasts zone state changes, system events, and device
    telemetry.
servers:
  - url: http://aris.local
    description: Local network (mDNS)
  - url: http://{brainIp}
    description: Local network (IP address)
    variables:
      brainIp:
        default: 192.168.1.100
        description: Your Aris Brain's IP address
security: []
tags:
  - name: Health
    description: Health check and readiness endpoints
  - name: System
    description: System-wide state and mode control
  - name: Zones
    description: Zone management, setpoints, and temperature control
  - name: DHW
    description: Domestic Hot Water tank status and history
  - name: TES
    description: Thermal Energy Storage tank status
  - name: HCU
    description: Hydronic Control Unit status
  - name: Heat Pumps
    description: Heat pump telemetry and diagnostics
  - name: FCUs
    description: Fan Coil Unit telemetry and status
  - name: Weather
    description: Weather data and forecasts
  - name: Events
    description: System event log and audit trail
  - name: Metrics
    description: VictoriaMetrics time-series data proxy
  - name: Prometheus
    description: Prometheus-compatible API for Grafana
  - name: Tokens
    description: API token management
  - name: Config
    description: System configuration (read-only)
  - name: Firmware
    description: FCU firmware OTA updates
paths:
  /api/hcu:
    get:
      tags:
        - HCU
      summary: Get HCU status
      description: >-
        Returns current hydronic control unit status including mode,
        temperatures, and efficiency.
      operationId: getHCUStatus
      responses:
        '200':
          description: HCU status
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HCUStatus'
        '401':
          $ref: '#/components/responses/Unauthorized'
        '503':
          description: HCU service not available
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
      security:
        - bearerAuth: []
components:
  schemas:
    HCUStatus:
      type: object
      properties:
        hcuId:
          type: string
          description: Unique identifier for the HCU
          example: hcu_main
        sourceType:
          type: string
          enum:
            - heat_pump
            - district_interface
          example: heat_pump
        mode:
          type: string
          enum:
            - heat
            - cool
            - dhw_charge
            - idle
          description: Resolved operating state - "heat", "cool", "dhw_charge", or "idle"
          example: heat
        state:
          type: string
          enum:
            - running
            - standby
            - defrost
            - fault
          description: Operational state - "running", "standby", "defrost", or "fault"
          example: running
        supplyTempC:
          type: number
          description: Temperature of water leaving HCU to the system
          example: 48.5
        returnTempC:
          type: number
          description: Temperature of water returning to HCU. Used for energy calculations.
          example: 42
        flowRateLpm:
          type: number
          description: Current flow rate through the source side (liters per minute)
          example: 4.2
        thermalPowerKw:
          type: number
          description: Real-time thermal output - the useful energy moving into the water
          example: 12.5
        electricalPowerKw:
          type: number
          description: >-
            Real-time electrical input - total power draw including compressor,
            pumps, electronics
          example: 3.2
        lifetimeThermalKwh:
          type: number
          description: Total accumulated thermal energy delivered
          example: 1420.5
        lifetimeElecKwh:
          type: number
          description: Total accumulated electricity consumed
          example: 450.2
        copInstant:
          type: number
          description: >
            Real-time efficiency (thermal/electrical). Only present when
            running.

            COP of 3.0 = 300% efficient vs resistance heating.
          example: 3.9
        outdoorTempC:
          type: number
          description: Outdoor ambient temperature
          example: -2.5
        backupHeaterActive:
          type: boolean
          description: True if electric backup heater is currently energized
          example: false
        activeFaults:
          type: array
          items:
            type: string
          description: List of active fault codes
          example: []
    Error:
      type: object
      properties:
        error:
          type: string
          description: Error type
        message:
          type: string
          description: Human-readable error message
        hint:
          type: string
          description: Suggestion for resolving the error
  responses:
    Unauthorized:
      description: Missing or invalid authentication
      content:
        application/json:
          schema:
            type: object
            properties:
              error:
                type: string
                example: Unauthorized
              message:
                type: string
                example: Valid authentication required
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: Session token or API token

````