HyHeat

HyHeat is a premium, state-of-the-art ESP32-based smart thermostat system designed specifically for campervans and RVs equipped with a hydronic furnace (e.g., Webasto, Eberspächer, or Aqua-Hot) plumbed in line with the engine's coolant loop.

By utilizing dual-thermostat climate logic, HyHeat seamlessly harvests "free" waste engine heat while driving or hot-camping, automatically transitioning back to the combustion furnace only when needed. It hosts a gorgeous, glassmorphic Progressive Web App (PWA) directly from the ESP32's flash storage, allowing full-screen offline-capable dashboard control on mobile phones or tablets.

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🌟 Key Features

• Dual-Thermostat Logic:
  • Engine Heat Thermostat: Actively monitors the engine coolant loop. When coolant is hot (e.g., above 55°C), it leverages this "free" waste heat by running only the matrix fan, allowing a configurable cabin temperature overshoot to store thermal energy.
  • Furnace Thermostat: Safely fires up the hydronic combustion furnace and matrix fan when waste engine heat is unavailable.
• Equipment Protection & Safety:
  • Strict configurable minimum runtimes (e.g., 15 minutes for the furnace to prevent short-cycling and carbon build-up).
  • Configurable hysteresis/deadbands and overrun values to minimize relay chatter.
• Self-Healing Sensor Health Check:
  • Dedicated automated interval checks monitor temperature readings.
  • If a sensor bus lockup or NaN reading is detected for 10 consecutive cycles (100 seconds), a dedicated power GPIO pin performs a hard power-cycle of the sensor bus to automatically recover.
• Luxury Glassmorphic PWA Web Interface:
  • Served directly from the ESP32 via a custom high-performance web_host ESPHome component.
  • Premium Outfit typography, fluid interactive double-handle temperature dial, SVG-rendered active glows, and hardware-accelerated animations.
  • Fully installable PWA with full-screen standalone capability, custom assets, service worker caching, and theme styling.
• Real-time UDP Telemetry:
  • Pushes InfluxDB line-protocol statistics via UDP for instant Grafana/InfluxDB dashboard visualization.
  • Tracks uptime, exact duty times for the fan and furnace, sensor readings, and setpoints.
  • IP and port are dynamically configurable inside the web interface without re-flashing.
• OTA Firmware Updates: Supported natively via ESPHome.

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🔌 Hardware Architecture

HyHeat runs on an ESP32 DevKit board connected to two relays and two temperature sensors.

1. Temperature Sensors

• Cabin Sensor (DHT22): Placed in the living/sleeping quarters. Measures ambient cabin temperature and relative humidity. Powered via a GPIO-controlled transistor/switch to allow hard-reboots.
• Heater Loop Sensor (NTC Thermistor): Placed on the engine coolant line entering the interior heat exchanger. Calibrated via a standard voltage divider (upstream configuration, 2.2k ohm series resistor) using the native Steinhart-Hart converter filter.

2. Relays

• Furnace Relay: Controls the hydronic furnace ignition line. Flipped on and kept on for the duration of the burn cycle.
• Fan Relay: Powers the matrix heat-exchanger fan, allowing it to run independently when engine waste heat is harvested or in furnace-only mode.

3. GPIO Pinout (Default Configuration)

Pin	Function	Description
GPIO18	Cabin Temp Input	Connected to the DHT22 data line
GPIO34	Heater Temp Input	ADC input connected to the NTC thermistor divider
GPIO21	Sensor Power	Controls VCC to the DHT22/thermistor for hardware reset
GPIO16	Furnace Relay	High triggers hydronic furnace burn
GPIO17	Fan Relay	High triggers matrix radiator fan
GPIO23	Status LED	System diagnostic LED indicator

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🛠️ ESPHome Configuration & Setup

HyHeat is built on a clean, modern ESPHome YAML definition leveraging custom external components.

1. File Structure

├── hyheat.yaml              # Core ESPHome configuration definitions
├── secrets.yaml             # Private credentials (WiFi, API keys, etc.)
├── LICENSE                  # MIT License
├── README.md                # This documentation
├── data/
│   └── htdocs/              # Static web interface files
│       ├── thermostat.html  # Main glassmorphic interface
│       ├── sw.js            # PWA service worker
│       ├── manifest.webmanifest # PWA configuration manifest
│       ├── apple-touch-icon.png # Generated app icon (192x192 transparent PNG)
│       └── favicon.ico      # Multi-resolution favicon bundle

2. Configure secrets.yaml

Create a secrets.yaml file (copied from secrets.yaml.example if available) and fill in your network credentials:

wifi_ssid: "Your_WiFi_SSID"
wifi_password: "Your_WiFi_Password"
api_encryption_key: "Generated_ESPHome_API_Key"
ota_password: "Your_OTA_Password"

3. Compile and Flash

Make sure you have ESPHome installed on your computer.

# Verify the configuration syntax is correct
esphome config hyheat.yaml

# Compile the firmware and upload it to your ESP32
esphome run hyheat.yaml

Once flashed, the ESP32 will connect to your WiFi network and host the web interface at http://hyheat.local/thermostat or via its assigned DHCP IP address.

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📲 Web Interface & PWA Installation

The PWA is designed with a premium, mobile-first dashboard aesthetic:

• Dial Control: The outer ring acts as a double-handle dial. Grab the Orange handle to adjust the Furnace Setpoint and the Gold handle to adjust the Engine Waste Heat Setpoint.
• Operating Modes:
  • Off: Turns all thermostats and demands off.
  • Engine: Turns on only the Engine Heat Thermostat (runs fan using waste coolant heat).
  • Auto: Standard smart thermostat operation. Runs the matrix fan on engine heat if coolant $>55^\circ\text{C}$; if coolant drops and cabin is cold, it fires up the furnace.
• Fan Mode: Toggle between Auto (thermostat-controlled fanning) and On (continuous cabin air circulation).

📱 Installing on Mobile Devices (iOS & Android)

1. Navigate to http://hyheat.local/thermostat in Safari (iOS) or Chrome (Android).
2. Tap the Share button (iOS) or the Menu button (Android).
3. Select Add to Home Screen.
4. HyHeat will now appear on your device's home screen with the beautiful premium icon and run in standalone, full-screen mode like a native app.

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📊 UDP Telemetry Payload

HyHeat sends real-time statistics in InfluxDB line-protocol format. The payload is constructed and optimized to fit into a single MTU:

hyheat,host=HyHeat furnace_relay=F,fan_relay=T,fan_override=F,has_residual_heat=T,engine_thermostat_on=T,furnace_thermostat_on=T,uptime=3624i,fan_on_s=120i,furnace_on_s=0i,cabin_temp=21.4,cabin_humidity=42.1,heater_loop_temp=62.8,furnace_target_temp=19.0,engine_target_temp=24.0,min_residual_heat=55.0

You can point these logs to a UDP listener in InfluxDB (port 8089 by default) to build dashboards monitoring fuel efficiency, heating duties, and temperature curves in real time.