Volcano Thermostat
The Legom Volcano Intelligent Thermostat RB-2305HT is a room thermostat designed for domestic water-based underfloor heating systems, supporting both individual room temperature control and whole-household temperature management. Available in three variants — RT-V1, RT-V2, and RT-V3 — in White, Black, and Grey finishes, the Volcano series features a circular display panel in an 86mm square housing with a clean, minimal aesthetic suited to modern interiors.
With a wide operating voltage of 100–240VAC, an NTC temperature sensor supporting both internal and external probe configurations, and direct compatibility with thermal actuators, heat source equipment, and the Legom base station ecosystem, the RB-2305HT provides flexible installation for standalone zone control or centralized multi-room systems. Temperature control accuracy is ±1°C across an internal range of 5°C to 35°C and an external probe range of 5°C to 60°C.
Key Benefits
- Wide voltage compatibility – Operates on 100–240VAC at 50/60Hz, making it compatible with both European and international mains voltage systems without modification
- Internal and external sensor modes – Supports three sensor configurations: internal sensor only (room air temperature), external sensor only (floor surface temperature), or both simultaneously — using the internal sensor to control setpoint and the external sensor to limit maximum floor temperature
- Base station compatible – Can be connected directly to thermal actuators and heat source equipment, or integrated with the Legom BS-Y6 or TCC base station for centralized multi-room monitoring and control
- High and low temperature protection – Built-in protection triggers automatic load shutdown above a configurable high-temperature limit (H3: 30–60°C, default 45°C) and automatic load activation below a configurable low-temperature limit (H4: 5–10°C, default 5°C)
- Valve protection function – Included as standard to prevent thermal actuator valves from seizing during extended periods of inactivity
- Advanced parameter settings – Four configurable parameters (H1 temperature compensation, H2 start-up temperature difference, H3 high temp protection, H4 low temp protection) accessible via the button interface
- Three colour variants – Available in White, Black, and Grey to match different interior design requirements
- PC flame retardant housing – 86 × 86 × 12.8mm slim panel designed for standard concealed wall box installation
- OEM and ODM customization available – Housing color, branding, and configuration can be customized for distributor requirements
Technical Specifications
| Parameter | Specification |
|---|---|
| Model | RB-2305HT (RT-V1 / RT-V2 / RT-V3) |
| Operating Voltage | 100–240VAC ~ 50/60Hz |
| Temperature Control Range | Internal: 5°C ~ 35°C / External: 5°C ~ 60°C |
| Temperature Control Accuracy | ± 1°C |
| Temperature Sensor | NTC |
| Load Current | 3A (MAX) |
| Housing Material | PC flame retardant |
| Dimensions | 86 × 86 × 12.8mm |
| Color Options | White / Black / Grey |
Advanced Settings Parameters
| Code | Function | Default | Adjustable Range |
|---|---|---|---|
| H1 | Temperature compensation | 0°C | -9°C ~ +9°C |
| H2 | Start-up temperature difference | 2°C | 0°C ~ 9°C |
| H3 | High temperature protection | 45°C | 30°C ~ 60°C |
| H4 | Low temperature protection | 5°C | 5°C ~ 10°C |
Error Codes
| Code | Meaning |
|---|---|
| E1 | Internal sensor short circuit |
| E2 | Internal sensor open circuit |
| E3 | External sensor short circuit |
| E4 | External sensor open circuit or not connected |
Application & Use Cases
- Underfloor heating zone control – The primary application. Installed in each room to sense air temperature and command the corresponding thermal actuator on the manifold to open or close the zone valve, maintaining the room at the set temperature
- Floor surface temperature limiting – When used in ALL sensor mode, the internal sensor controls the room air setpoint while the external floor probe prevents the floor surface temperature from exceeding the H3 high temperature protection value — important for wood, laminate, and tile floors with specified maximum surface temperatures
- Centralized multi-room heating systems – Connected to the Legom BS-Y6 (6-zone) or TCC (8-zone) base station for a complete room-by-room heating control system with central pump and boiler management
- Standalone single-zone control – Can be wired directly to a thermal actuator and heat source without a base station for simple single-room heating control installations
- Frost protection in unoccupied rooms – The H4 low temperature protection parameter activates heating automatically when room temperature falls below the set threshold, protecting pipes and structure from frost damage in temporarily unoccupied spaces
Installation Notes
- Install the thermostat in a standard concealed wall box at a height of 1.4 metres from the floor
- Avoid installing in locations exposed to direct sunlight, drafts, or heat sources — these will cause inaccurate temperature readings and incorrect zone control
- Installation must be carried out by qualified electrical personnel. Ensure the front-end power supply is fitted with an independent switch or socket so the system can be safely isolated
- To disassemble: insert a 3.5mm flat screwdriver along the panel seam and gently lever open. Move the panel up and down to separate it from the bottom shell
- Connect wiring according to the diagram printed on the bottom shell. Terminal functions: 1 (NO valve), 2 (NC valve), 3 (L line), 4 (N line), 9/10 (dry contact). For external sensor version, add terminals 1/2 (NTC), 3 (NO), 4 (NC), 5 (L), 6 (N)
- Fasten the bottom shell to the wall box with screws, connect the display board to the power board via the cable socket, then fit the panel
- Do not exceed the 3A maximum load current. Overload installation is prohibited
- Factory reset: within 20 seconds of powering off, press Up and Down simultaneously for 5 seconds to restore factory defaults
Frequently Asked Questions
What is the difference between internal sensor, external sensor, and ALL modes?
In Internal (IN) mode, the thermostat uses only its built-in air temperature sensor to measure room temperature and control the heating zone. In External (OUT) mode, it uses only the floor-mounted NTC probe — useful for floor surface temperature control in sensitive floor coverings. In ALL mode, the internal sensor controls the room air temperature setpoint while the external probe acts as a floor temperature limiter — the system stops heating if the floor reaches the H3 protection value, even if the room air temperature is still below the setpoint. ALL mode is the recommended setting when an external probe is fitted in underfloor heating installations with wood or laminate floors.
Can the Volcano thermostat work without a base station?
Yes. The RB-2305HT can be wired directly to a thermal actuator and heat source equipment as a standalone single-zone controller without any base station. The base station is only required when multiple thermostats need to be centrally coordinated with shared pump and boiler control outputs.
What do the E1, E2, E3, E4 error codes mean?
E1 indicates a short circuit in the internal (built-in) temperature sensor. E2 indicates an open circuit in the internal sensor. E3 indicates a short circuit in the external (floor probe) sensor. E4 indicates an open circuit or a disconnected external sensor. When any error code appears, the thermostat stops operating until the fault is resolved. If E3 or E4 appears because no external probe is connected but external sensor mode was selected, switch to internal sensor mode via the advanced settings or perform a factory reset.
What is the valve protection function?
The valve protection function periodically activates the thermal actuator valve during extended periods when no heating is called for, preventing the valve from seizing in one position due to prolonged inactivity. This is particularly important for systems that are shut down seasonally and where the actuator valve may otherwise remain fully closed for months.
How do I adjust the temperature compensation (H1)?
If the thermostat consistently reads higher or lower than the actual room temperature, the H1 compensation parameter can correct the displayed value by up to ±9°C. Enter advanced settings by long-pressing the Mode button while powered on, navigate to H1, and adjust using the Up/Down buttons. The correction is applied to the displayed room temperature reading and affects when the heating switches on and off.
Is the Volcano thermostat compatible with the Legom base station?
Yes. The RB-2305HT is designed to work with the Legom BS-Y6 6-zone base station and the TCC 8-zone base station for centralized multi-room heating control. When connected to a base station, the thermostat’s switching commands are forwarded to the base station, which manages the pump and boiler circuit centrally.
OEM & ODM Customization
Legom supports OEM and ODM services for the Volcano Thermostat series. Housing color, branding, and configuration parameters can be customized for distributor and system integrator requirements. All customization projects are handled with strict confidentiality. Contact us via WhatsApp or info@legomsmart.com.
User Manual
Product information last reviewed by the Legom Technical Team. For the most current specifications, refer to the official datasheet or contact our sales team.
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