Terma MOA Blue ESPHome Integration

Control your Terma MOA Blue radiator heating element via Home Assistant using an ESP32 and ESPHome.

Overview

The Terma MOA Blue is a Bluetooth-controlled electric heating element designed for towel radiators and other heating applications. This project allows you to integrate it with Home Assistant, providing:

• Climate entity - Full thermostat control with presets (Home, Away, Boost)
• Temperature monitoring - Via external DHT22 sensor (recommended) or the radiator's built-in sensor
• Manual control - On/off switch for direct control
• Status monitoring - Connection status, heating state, and radiator element temperature

Features

• Bluetooth Low Energy (BLE) connection with persistent bonding
• Climate entity for Home Assistant thermostat integration
• External DHT22 temperature/humidity sensor support
• Automatic reconnection after power loss
• Manual override switch
• Radiator element temperature monitoring
• Room temperature and humidity monitoring
• Presets: Home (21°C), Away (16°C), Boost (24°C)

Requirements

Hardware

• ESP32 development board (e.g., ESP32-WROOM-32, ESP32-DevKitC) - It may work on others fine but untested.
• Terma MOA Blue heating element
• DHT22 temperature/humidity sensor (recommended)
• 10kΩ resistor (for DHT22 pull-up, may be required depending on your module)
• Jumper wires
• USB cable for programming

Software

• ESPHome 2024.1.0 or later
• Home Assistant (optional, but recommended)

Wiring

DHT22 Sensor Wiring

Connect the DHT22 sensor to your ESP32 as follows:

DHT22 Pin    ESP32 Pin
─────────    ─────────
VCC    ───── 3.3V
GND    ───── GND
DATA   ───── GPIO4 (configurable)

Note: Some DHT22 modules require a 10kΩ pull-up resistor between VCC (3.3V) and the DATA pin for reliable readings. Modules with a built-in PCB typically include this resistor. The module tested does not require this and is shown in the picture above.

Installation

1. Prepare the Files

Copy both files to your ESPHome configuration directory:

• terma-moa-blue.yaml - Main configuration file - import into ESPHome as normal.
• terma_ble_helper.h - BLE helper header file - copy to the config\esphome directory in home assistant. Note: This file is required for persistent bluetooth connections.

2. Configure the YAML

Edit terma-moa-blue.yaml and update the following:

substitutions:
  device_name: terma-moa-blue
  friendly_name: "Bathroom Radiator"
  radiator_mac: "XX:XX:XX:XX:XX:XX"  # Your radiator's MAC address
  dht_pin: GPIO4                      # Change if using a different pin

Finding Your Radiator's MAC Address

You can find the MAC address using:

• Android Settings: Go to Settings → Bluetooth → Paired devices (after pairing with the Terma app)
• Android: Use the nRF Connect app to scan for nearby BLE devices. Look for "MOA Blue TERMA".
• ESPHome Logs: Enable the esp32_ble_tracker component and check the logs for discovered devices.

3. Configure Secrets

Ensure your secrets.yaml contains:

wifi_ssid: "YourWiFiNetwork"
wifi_password: "YourWiFiPassword"
ap_password: "FallbackAPPassword"
# Optional:
# api_encryption_key: "your-api-key"
# ota_password: "your-ota-password"

4. First-Time Pairing

Important: The first connection requires the radiator to be in pairing mode.

1. Flash the ESPHome configuration to your ESP32

2. Put the Terma MOA Blue into pairing mode:

   • Press and hold the temperature button for 5 seconds on the heating element until the LED flashes
   • Refer to your Terma MOA Blue manual for specific instructions

3. Start the device within bluetooth range of the radiator

4. Monitor the logs - you should see:

   BLE client connected - requesting encryption...
   Passkey requested by radiator - sending 123456
   BLE connection ready
   

5. Once paired, the ESP32 will automatically reconnect even after power cycles

5. Add to Home Assistant

The device should be automatically discovered by Home Assistant. If not:

1. Go to Settings → Devices & Services
2. Click "Add Integration"
3. Search for "ESPHome"
4. Enter your device's IP address or hostname

Configuration Options

Using Without a DHT22 Sensor

If you don't have a DHT22 sensor, you can use the radiator's built-in temperature sensor instead.

1. Comment out or remove the DHT22 sensor section
2. Change the climate entity sensor reference:

climate:
  - platform: thermostat
    name: "Bathroom Heater"
    sensor: room_temp_raw  # Use radiator's built-in sensor
    # ... rest of config

Note: The radiator's built-in sensor is less accurate than an external DHT22, as it's affected by the radiator's own heat.

Adjusting Temperature Presets

Modify the preset temperatures in the climate section:

preset:
  - name: Home
    default_target_temperature_low: 21  # Default home temperature
  - name: Away
    default_target_temperature_low: 16  # Away/eco temperature
  - name: Boost
    default_target_temperature_low: 24  # Boost temperature

Adjusting Deadband

The deadband controls when heating starts/stops relative to the target temperature:

heat_deadband: 0.5  # Start heating 0.5°C below target
heat_overrun: 0.5   # Stop heating 0.5°C above target

Entities Exposed to Home Assistant

Entity	Type	Description
Bathroom Heater	Climate	Main thermostat control
Room Temperature	Sensor	DHT22 temperature reading
Room Humidity	Sensor	DHT22 humidity reading
Radiator Room Sensor	Sensor	Radiator's built-in temperature sensor
Radiator Element Temperature	Sensor	Heating element temperature
Radiator Power (Manual)	Switch	Direct on/off control
Heating Active	Binary Sensor	Whether radiator is currently heating
Radiator BLE Connected	Binary Sensor	BLE connection status
Radiator BLE Presence	Binary Sensor	Whether radiator is in BLE range
Radiator Status	Text Sensor	Human-readable status
Clear BLE Bonds	Button	Reset Bluetooth pairing
Restart	Button	Restart the ESP32

Troubleshooting

Error reading char, status=5

This indicates an authentication error. The radiator requires encryption for reading characteristics.

Solution:

1. Press "Clear BLE Bonds" in Home Assistant
2. Restart the ESP32
3. Put the radiator into pairing mode
4. Wait for reconnection

Cannot connect after power cycle

The ESP32 stores bonding information, but sometimes it needs to be re-established.

Solution:

1. Clear bonds on both devices:
   • Press "Clear BLE Bonds" in Home Assistant
   • Reset pairing on the radiator (hold button for 5 seconds until the LED flashes)
2. Restart the ESP32
3. Put the radiator in pairing mode

DHT22 readings are unstable or not using the same module pictured

Solutions:

• Add a 10kΩ pull-up resistor between VCC and DATA
• Use shorter wires (under 1 meter)
• Ensure stable 3.3V power supply
• Try a different GPIO pin

Radiator disconnects frequently

BLE range is limited, especially through walls.

Solutions:

• Move the ESP32 closer to the radiator
• Use an ESP32 with an external antenna
• Reduce WiFi interference (BLE and WiFi share the 2.4GHz band)

Technical Details

BLE Characteristics

UUID	Description
d97352b0-d19e-11e2-9e96-0800200c9a66	Service UUID
d97352b1-d19e-11e2-9e96-0800200c9a66	Room temperature (current + target)
d97352b2-d19e-11e2-9e96-0800200c9a66	Heater element temperature (current + target)
d97352b3-d19e-11e2-9e96-0800200c9a66	Operating mode

Operating Modes

Mode	Description
0	Off
5	Manual - Room temperature control (15-30°C)
6	Manual - Heater element control (30-60°C)
7	Schedule - Room temperature
8	Schedule - Heater element

Temperature Encoding

Temperatures are encoded as 4 bytes:

• Bytes 0-1: Current temperature × 10
• Bytes 2-3: Target temperature × 10

Example: 21.5°C = 215 = 0x00 0xD7

License

This project is provided as-is for personal use. The Terma MOA Blue protocol was reverse-engineered from community efforts.

Acknowledgments

• Home Assistant Community - Protocol reverse engineering
• homebridge-TERMA-MOA-Blue - A great homekit solution from J1mbo
• ESPHome - Excellent IoT firmware framework
• Anthropic Claude - AI assistance in developing this integration to solve the bluetooth persistent connection pain

Contributing

Contributions are welcome! Please feel free to submit issues or pull requests.

Disclaimer

This is an unofficial integration and is not affiliated with or endorsed by Terma. Use at your own risk. Always follow safety guidelines when working with electrical heating equipment.