Three-way mixing valve Termojet, DN20, kvs-6.3 female thread

Three-way rotary mixing valve Termojet DN20 is a fitting with a rotary plug and internal thread Rp ¾" for automatic stepless mixing of heating fluid. Flow coefficient Kvs 6,3 m³/h, working pressure PN 10 bar, temperature range –10…+110°C. Body made of brass CW617N, EPDM seals, leakage less than 0.1%. The valve is designed for actuator mounting and provides proportional supply temperature control for heating or underfloor heating circuits.

Technical Specifications

Operating Principle

The valve has three ports: A — hot fluid supply from the boiler, B — return from the heating circuit, AB — outlet to the circuit. The actuator rotates the plug within a 0–90° range in response to a control signal from the controller. Changing the rotation angle smoothly varies the ratio of hot and return flows — the fluid temperature at outlet AB is regulated steplessly. EPDM seals ensure leakage of less than 0.1% of Kvs in the closed position.

Applications

• Underfloor heating. DN20 Kvs 6,3 — compact size for a mixing unit of underfloor circuits covering up to 80 m²: maintains supply temperature of 35–43°C regardless of boiler temperature.
• Mixed systems — radiators + underfloor. One valve for the underfloor heating circuit when radiators operating at higher temperatures are present in the same system.
• Weather-compensated control. Paired with Termojet 411 actuator (0–10V, 24V) and a weather-compensating controller, the valve smoothly reduces supply temperature as outdoor temperature rises — saving gas or electricity.
• Boiler room with multiple circuits. Compact DN20 for small residential systems; for higher flow rates — DN25 and DN32 models.
• Manual balancing. Without an actuator, the valve can be fixed in any position using the handle for static adjustment.

Advantages of Termojet DN20

• Brass body CW617N — long service life and manufacturing precision on par with leading European equivalents.
• Leakage less than 0.1% — minimal heat losses with the plug closed or partially open.
• Standard actuator mounting — install actuators 401N, 405N and 411 without additional adapters.
• EPDM seals — resistance to heating fluids with glycol additives up to 50%.
• Compact dimensions (H 82 mm, L1 80 mm) — easy installation in confined heating unit spaces.

Compatible Actuators

The plug torque of the Termojet DN20 valve is less than 3 Nm. All actuators listed below have a twofold torque reserve (6 Nm):

• Actuator Termojet 401N (3-point, 230V, 120 s) — for fast zone control and simple boiler controllers with 3-position output.
• Actuator Termojet 405N (3-point, 230V, 60 s) — smoother control with reduced travel time.
• Actuator Termojet 411 (0–10V, 24V) — for weather-compensated automation, smart home systems and heat pump integration.

Valve and Heat Pump

Heat pumps achieve maximum efficiency at a heating fluid temperature of 35–45°C — exactly the range in which underfloor heating operates. The three-way mixing valve Termojet DN20 Kvs 6,3 paired with actuator 411 (0–10V) allows smooth regulation of supply temperature and maintains the optimal thermal operating mode of the system. Learn more about integrated heat pump solutions at the Termojet heat pumps website.

Frequently Asked Questions

How to choose between DN20 Kvs 6,3 and DN25 Kvs 10?
DN20 Kvs 6,3 is suitable for circuits with flow rates up to 3–4 m³/h (underfloor heating up to 80 m² or a low-capacity system). DN25 Kvs 10 — for larger circuits or systems with higher flow rates. Approximate calculation: Kvs ≥ Q / √ΔP, where Q is flow rate in m³/h, ΔP is the pressure drop across the valve 0.3–0.5 bar.

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