Three-way mixing valve Termojet, DN20, kvs-2,5 male thread

Three-way rotary mixing valve Termojet DN20 is a compact fitting with a rotary plug and external thread G 3/4" for automatic heating fluid temperature control in heating systems. Flow coefficient Kvs 2,5 m³/h, working pressure PN 10 bar, operating temperature range –10…+110°C. The valve is designed for actuator mounting and allows smooth regulation of the hot and return fluid ratio at the circuit outlet.

Technical Specifications

Operating Principle

The valve has three ports: A — hot supply from the boiler, B — return from the circuit, AB — outlet to the heating circuit or underfloor heating. When the plug rotates 90° on the actuator's command, the ratio of hot and return flows changes smoothly — the supply temperature to the circuit is regulated steplessly. EPDM seals guarantee leakage of less than 0.1% of Kvs in the closed position.

Applications

• Underfloor heating for small areas. DN20, Kvs 2,5 — optimal size for a mixing unit of a floor circuit covering up to 60–80 m²: maintains supply temperature of 35–45°C regardless of the boiler operating mode.
• Mixed systems in small buildings. Separate underfloor heating circuit from a boiler with radiators — one DN20 valve for controlling the floor circuit.
• Weather-compensated control. Paired with actuator 411 (0–10V) and a weather-compensating controller, the valve smoothly adjusts the supply temperature depending on the outdoor temperature.
• Manual balancing. Without an actuator, the valve can be fixed in any position — for static temperature adjustment without automation.
• Replacement of an outdated valve. Standard G 3/4" thread and compact dimensions allow installation in an already assembled system without reworking the pipework.

Advantages of Termojet DN20

• Brass body CW617N — corrosion resistance and manufacturing precision on par with leading equivalents.
• Leakage less than 0.1% — reliable tightness with the plug closed.
• Compact DN20 — minimum required size for small systems: less material, less space in the boiler room.
• Standard actuator mounting — compatible with actuators of the 401N, 405N, 411 series without adapters.
• EPDM seals — resistance to glycol-based heating fluids and elevated temperatures.

Compatible Actuators

For automation of the Termojet DN20 Kvs 2,5 valve, actuators with a torque of at least 6 Nm are suitable (valve plug torque — less than 3 Nm, twofold reserve):

• Actuator Termojet 401N (3-point, 230V) — for fast control and simple boiler controllers.
• Actuator Termojet 405N (3-point, 230V) — smoother control, standard choice for most systems.
• Actuator Termojet 411 (0–10V, 24V) — for weather-compensated automation, smart home systems and heat pump installations.

Valve and Heat Pump

Heat pumps operate most efficiently at low fluid temperatures — 35–45°C. The three-way mixing valve DN20 Kvs 2,5 allows precise maintenance of this temperature in the floor circuit, even if the heat pump outputs 45–50°C. Paired with actuator 411 (0–10V), the valve provides smooth proportional control, increasing the efficiency of the entire system. Learn more at the Termojet heat pumps website.

Frequently Asked Questions

What is the difference between DN20 and DN25 for underfloor heating?
DN20 (Kvs 2,5) is suitable for floor circuits covering up to 60–80 m² and medium-capacity systems. DN25 (Kvs 6) — for larger installations or boiler rooms with higher heating fluid flow rates. If your circuit is larger, consider the Termojet DN25 Kvs 6 three-way valve.

Can the valve be installed without an actuator?
Yes. The valve handle can be fixed in any position — for manual static supply temperature adjustment. For automatic control, install one of the compatible actuators of the 401N, 405N or 411 series.