How to smart-enable an old towel dryer with a Shelly module or Zigbee protocol?

Prerequisites and diagnosis of your towel warmer

Before embarking on the installation of a home automation module, it is essential to know precisely the type of electric towel warmer you own. This will determine the most suitable integration method.

Identify the type of your towel warmer

There are mainly three configurations:

• Simple on/off towel warmer: a single switch, no electronic thermostat. This is the simplest configuration to automate.
• Towel warmer with mechanical thermostat: a rotary temperature adjustment knob. Can be automated on/off or via pilot wire.
• Towel warmer with pilot wire: an additional wire (often purple or black) allowing 4 control commands. The most complete solution for home automation.

Check the appliance's power

Note the power in watts indicated on the nameplate of your towel warmer (generally between 500W and 2000W). This information is crucial for choosing a home automation module with the appropriate switching capacity. An undersized module will overheat, age prematurely, and present a fire risk.

Check existing wiring

Open the connection box of your towel warmer (appliance switched off, circuit breaker cut). Count the wires: 3 wires (phase, neutral, earth) indicate a simple model. 4 wires (phase, neutral, earth + pilot wire) indicate a model compatible with centralized control.

Shelly Solution: the universal Wi-Fi module

Shelly modules have become the mainstream standard for automating existing electrical appliances. Compact, affordable (€10 to €20), and with an open API, they integrate natively into major home automation platforms.

Which Shelly model to choose?

Shelly 1 installation for on/off control

The Shelly 1 is wired into the recessed box or the towel warmer's connection box. The principle is simple: the module is inserted on the phase between the electrical panel and the appliance, allowing the power supply to be cut and restored remotely.

Simplified wiring diagram:

• L (input) terminal → Phase coming from the panel
• O (output) terminal → Phase going to the towel warmer
• N terminal → Neutral (necessary to power the module)
• SW terminal → Optional: existing physical switch

Once wired, the Shelly creates its own temporary Wi-Fi network. Connect to it from your smartphone, configure your home Wi-Fi network, and the device is accessible from the Shelly Cloud application or directly via its local API.

Zigbee Solution: stability and network independence

If Wi-Fi experiences interference in your bathroom or if you prefer a more robust mesh protocol, Zigbee is an excellent alternative. Unlike Wi-Fi, Zigbee forms a mesh network where each device can act as a relay, ensuring superior coverage and stability.

Necessary equipment

To use Zigbee, you need two components:

• A Zigbee coordinator: a Zigbee USB stick (Sonoff Zigbee Dongle-P or ConBee II) connected to a Raspberry Pi or a NAS running Home Assistant or Zigbee2MQTT.
• A Zigbee switching module: SONOFF ZBMINIL2, Aqara SSM-U02, or similar. These modules, more compact than their Wi-Fi counterparts, integrate discreetly into recessed boxes.

Advantages of Zigbee vs Wi-Fi for this use

• Lower latency: switching is almost instantaneous (less than 100ms)
• Module's own consumption: 0.5W vs 1-2W for Wi-Fi
• No cloud dependence: everything works locally via the coordinator
• Mesh network: range automatically extends with each added Zigbee device
• Stability: no disconnections due to saturation of 2.4 GHz Wi-Fi networks

Installation with Zigbee2MQTT

Zigbee2MQTT is open-source software that bridges your Zigbee coordinator and Home Assistant's MQTT broker. Once installed (available as a Home Assistant add-on), pairing a new Zigbee module takes a few seconds: activate pairing mode in the interface, press the module button for 5 seconds, and it automatically appears in your dashboard.

Integrating the pilot wire for advanced control

If your electric towel warmer is equipped with a pilot wire, you gain a level of control far superior to simple on/off. The pilot wire allows you to send 4 distinct commands to the appliance via specific electrical signals.

The 4 pilot wire commands

Automating the pilot wire with a Shelly 1 + diode

To send pilot wire commands via a Shelly module, you will need a Shelly 1 and a 1N4007 diode (a few cents in electronics stores). By associating or not associating the diode in series on the pilot wire, and by controlling the module's state (on/off), you can generate the 4 necessary signals. This technique, well documented in the French-speaking home automation community, nevertheless requires basic electronics knowledge.

For a ready-to-use solution without soldering, specialized modules such as the Qubino Flush Pilot Wire or the Nodon SIN-4-FP-21 (Zigbee, 4 native commands) manage the pilot wire natively and integrate directly into Home Assistant or Jeedom.

Integration into Home Assistant

Home Assistant (HA) is currently the leading open-source home automation platform. Free, local, and with a very active French-speaking community, it stands out as the natural choice for controlling your connected towel warmer.

Shelly Integration in Home Assistant

Since Home Assistant 2021.7, Shelly integration is native and does not require any third-party add-ons. If your Shelly module is on the same local network, Home Assistant automatically detects it via mDNS and offers to add it with a single click from Settings → Devices & Services → Integrations → Shelly.

Once added, your towel warmer appears as a switch entity in HA. You can add it to your dashboard, create automations, and monitor its real-time consumption (with Shelly Plus which includes a wattmeter).

Zigbee Integration with Zigbee2MQTT

Install the Zigbee2MQTT add-on from the Home Assistant store, configure your coordinator's USB port, and your paired Zigbee modules will automatically appear as entities in HA. The Nodon pilot wire module, for example, exposes a climate entity with the 4 modes directly selectable from the interface.

Home Assistant automation example

Here is an example of a YAML automation to automatically switch to Eco mode at night:

automation:
  - alias: "Towel warmer - Eco mode at night"
    trigger:
      - platform: time
        at: "22:30:00"
    action:
      - service: climate.set_preset_mode
        target:
          entity_id: climate.seche_serviette_sdb
        data:
          preset_mode: "eco"

  - alias: "Towel warmer - Comfort mode in the morning"
    trigger:
      - platform: time
        at: "06:30:00"
    action:
      - service: climate.set_preset_mode
        target:
          entity_id: climate.seche_serviette_sdb
        data:
          preset_mode: "comfort"

Integration into Jeedom

Jeedom is the main French alternative to Home Assistant. Although its interface is less modern, it offers proven robustness and a very rich plugin ecosystem, particularly suited to the French market.

Shelly Plugin for Jeedom

The official Shelly Manager plugin (available on the Jeedom market, free) allows you to integrate all Shelly modules in a few minutes. Once the plugin is installed and configured with your module's IP address, your on/off commands and consumption data are automatically sent to Jeedom.

Zigbee Plugin for Jeedom

Jeedom's Zigbee plugin (compatible with Zigbee2MQTT) works similarly to Home Assistant integration. Module pairing is guided by an intuitive graphical interface, and the created entities can be directly used in Jeedom scenarios.

Creating a timed scenario in Jeedom

In Jeedom, scenarios allow you to program the towel warmer with minute-by-minute precision. Create a "Scheduling" type scenario and define your time slots: comfort mode from 6:30 AM to 8:00 AM and from 6:00 PM to 10:00 PM, eco mode the rest of the time, frost-protection mode during your absences detected via your alarm or geolocation.

Examples of Smart Automations

Once your connected towel warmer is set up, here are the most useful automations to implement to maximize your comfort and minimize your consumption.

🕐 Classic Timed Programming

The basics: comfort in the morning (6:30 AM-8:00 AM), eco during the day, comfort in the evening (6:00 PM-10:30 PM), frost protection at night. This single automation can reduce your towel warmer's consumption by 30 to 40% compared to continuous comfort mode operation.

📍 Presence/Absence Mode via Geolocation

Link your towel warmer's status to detected presence in your home. If all household members are absent, automatically switch to frost protection. Expected back in 30 minutes? Automatic switch to comfort mode.

☀️ Off-peak / Peak Hours Optimization

If you have an EDF subscription with off-peak hours, program your towel warmer's heating periods during advantageous tariff slots. In winter, well-managed thermal inertia can significantly reduce your bill.

🌡️ Coupling with a Temperature Sensor

Add a small Zigbee temperature/humidity sensor (Aqara WSDCGQ11LM, ~€15) in your bathroom. Create an automation that regulates the towel warmer according to the actual room temperature rather than a fixed schedule. Result: optimal comfort with minimal consumption.

Budget and solution comparison

Electrical Safety: Rules to Follow

Automating an electrical appliance in a bathroom is subject to strict safety rules that must be observed.

Bathroom Protection Zones

The NF C 15-100 standard defines protection zones around water points. In volume 1 (in the bathtub or shower) and volume 2 (less than 60 cm from the shower), only class III (very low voltage) appliances are allowed. Home automation modules (Shelly, Zigbee) must be installed outside these volumes, ideally in a flush-mounted box in volume 3 or outside the bathroom.

Module IP Rating

Check the IP rating of your home automation module before installation. In volume 2, a minimum IP44 rating is required. In volume 3, an IP21 rating is sufficient. Most Shelly and Zigbee modules are IP20 and must therefore only be installed in a closed box in volume 3.

Never Exceed the Module's Maximum Load

A home automation module whose maximum load is exceeded will overheat and pose a fire risk. For a 1500W towel warmer, use a module approved for at least 2000W with a safety margin. When in doubt, go for a higher-rated model rather than saving a few euros.