Caldera Sauna — Home Assistant integration

Local control of Relaxe Caldera infrared saunas over Bluetooth LE — no cloud, no account. Adds sauna controls to Home Assistant, and works through an ESPHome BLE proxy if the sauna is out of range of your HA host.

⚠️ Safety: Unofficial, as-is software with no warranty — and not a safety device. Never rely on it as your only safeguard. Follow all of the sauna manufacturer's safety instructions, including unplugging the sauna when it's not in use, and never run it unattended. See Safety & liability below.

Install (HACS)

1. In HACS → ⋮ → Custom repositories, add https://github.com/realark/caldera-ble as an Integration.
2. Search for Caldera Sauna, download it, and restart Home Assistant.
3. Open Settings → Devices & Services — your sauna should be discovered automatically. Click Configure to add it.

Disconnect the manufacturer's phone app from the sauna first — the sauna allows only one Bluetooth connection at a time.

That's it. You'll get:

• Climate — power on/off, current & target temperature
• Light — RGB mood light (color presets as effects)
• Switch — cabin lamp
• Number — session timer (minutes)

Manual install (without HACS)

Copy custom_components/caldera_sauna/ into your HA config/custom_components/ and restart.

How it works

Reverse-engineered from the manufacturer's Android app: the sauna exposes a cheap serial-over-BLE module (service FFF0, characteristic FFF1) speaking a plain ASCII protocol — no pairing, PIN, or auth. The integration talks to it through Home Assistant's Bluetooth stack, so both host adapters and ESPHome BLE proxies work. Full wire protocol: PROTOCOL.md.

The protocol logic lives in a standalone, hardware-independent Python library (caldera-sauna on PyPI); the Home Assistant integration is a thin layer on top.

Developing

src/caldera_sauna/
  protocol.py   pure codec (no I/O) — encode commands, decode status frames
  device.py     bleak + bleak-retry-connector transport (proxy-compatible)
  monitor.py    read-only CLI: scan, connect, print decoded state
scripts/          hardware probes / calibration tools (read-only unless noted)
tests/            unit tests for the codec (no hardware needed)
custom_components/caldera_sauna/   the Home Assistant integration

python3 -m venv .venv && . .venv/bin/activate
pip install -e ".[dev]"
pytest                       # codec tests, no hardware
ruff check src tests scripts custom_components

Device-specific info stays out of git — copy .env.example to .env and set your sauna's BLE address (find it with bluetoothctl scan on or nRF Connect). The scripts/ tools read .env; with no address set they scan by name (default Sauna). Read-only state monitor:

caldera-sauna-monitor        # scan by name, print decoded state; sends nothing

Releases are cut with ./release.sh <version> (bumps versions, publishes to PyPI, tags, pushes, and creates the GitHub release HACS installs from).

Safety & liability

This is free, unofficial, as-is software (see LICENSE). It comes with no warranty of any kind, and the authors accept no liability for any damage, injury, or loss arising from its use — including malfunction, incorrect readings, dropped or delayed commands, or a heater being left on.

This is not a safety device. Do not rely on it for safety-critical control of your sauna. Your sauna's own built-in thermostat, timer, and over-temperature protection are the safety layer — this software must never be your only line of defense. Don't run the sauna unattended, and follow the manufacturer's safety instructions. By using this software you accept full responsibility for the outcome.

Independent project — not affiliated with, endorsed by, or supported by Relaxe or Caldera. Reverse-engineered for personal interoperability.