Thermostatic three-way valve Termojet 3/4" male thread, kvs-1.6, temp - 20-43°C

The Termojet TMV121 thermostatic three-way valve is a passive mixing device with a built-in thermostat element that automatically maintains the set outlet temperature in the range of 20–43°C with an accuracy of ±2°C. Connection GZ ¾" (male thread), flow coefficient Kvs 1,6 m³/h, maximum static pressure — 10 bar. The valve operates without electrical power and requires no maintenance whatsoever.

Technical Specifications

Operating Principle

The valve's two separate inlets receive hot water (from a boiler or water heater) and cold water from the mains. The thermostat element in the body expands or contracts depending on the temperature of the mixed water at the outlet — and automatically adjusts the proportion of each flow, keeping the temperature within ±2°C of the set value. Anti-scald function: if the cold water supply suddenly stops, the valve automatically shuts off the hot flow — water at the point of use will not become dangerously hot. A tamper-proof cap prevents unauthorised adjustment of the set temperature limit.

Applications

• Underfloor heating. The 20–43°C series protects the polyethylene pipes of the floor circuit from overheating — the supply is maintained within a safe range regardless of the boiler or heat pump operating mode.
• Scald protection in bathrooms and showers. The valve guarantees that the mixed water temperature will never exceed the set limit, even when mains pressure fluctuates.
• Children's rooms, nurseries, hospitals, hotels. The tamper-proof cap securely locks the settings and prevents overheating in spaces with heightened safety requirements.
• Solar DHW systems. Protection against overheated water from a solar collector, where temperatures can significantly exceed the comfort limit.
• Hygienic safety. Maintaining the temperature in the recirculation circuit prevents the growth of dangerous micro-organisms in the pipework.

Advantages of the Termojet TMV121

• CW617N brass body — corrosion resistance and manufacturing precision on par with leading European equivalents.
• Temperature maintenance accuracy ±2°C — consistent comfort without overheating or overcooling.
• No electrical power — passive 24/7 operation with zero electricity costs.
• Automatic shut-off of the hot flow when cold water is lost — safety even in emergency network situations.
• GZ ¾" thread — the most common size for residential systems, standard installation without adapters.

TMV121 and the Heat Pump

Heat pumps generate coolant in the 30–55°C range — exactly the window in which underfloor heating operates most efficiently. The Termojet TMV121 valve in the 20–43°C series protects the floor circuit from peak temperatures during auxiliary heating or bivalent operation, allowing the heat pump to maintain an optimal efficiency coefficient. More about comprehensive solutions on the Termojet heat pumps website.

Frequently Asked Questions

Does the TMV121 require an actuator?
No. The thermostatic valve is passive: the thermostat element responds to temperature on its own without any electrical power. This is a significant advantage over motorised rotary valves in systems where automation is not provided. If you are interested in valves for actuators, see the Termojet valve catalogue or other thermostatic models in the series: TMV131 GZ 1" Kvs 1,6 and TMV231 GZ 1" Kvs 2,5.

What is the difference between the 20–43°C and 35–60°C series?
The 20–43°C series is for underfloor heating and low-temperature circuits where a mild supply temperature is required. The 35–60°C series is for DHW and shower points where scald protection is important with a hotter supply. Choose the series according to the heat source and intended use at the point of consumption.