Three-way mixing valve Termojet, DN40, kvs-25 female thread

Termojet DN40 three-way rotary mixing valve — a fitting with a rotary brass ball and internal thread Rp 1½" for automatic blending of heat-transfer fluid in large heating systems. Flow coefficient Kvs 25 m³/h, working pressure PN 10 bar, temperature range –10…+110°C. Body — brass CW617N, EPDM seals. The valve is designed for use with an actuator and provides smooth, stepless regulation of supply temperature.

Technical Specifications

Operating Principle

The valve has three ports: A — hot supply from the boiler or manifold, B — return fluid from the circuit, AB — outlet of mixed fluid to the heating system. The actuator rotates the ball from 0° to 90° on a controller signal — the proportion of hot and cooled flows changes smoothly, and the temperature at outlet AB is regulated steplessly. The linear flow characteristic Kvs 25 ensures precise metering over a wide flow range. EPDM seals guarantee leakage below 0.1% Kvs even during extended operation with glycol-based heat-transfer fluids.

Applications

• Large boiler rooms (60–120 kW). Kvs 25 and DN40 cover the heat-transfer fluid flow rates in commercial and industrial facilities — office buildings, hotels, small industrial workshops.
• Main mixing unit of a boiler room. A single DN40 valve replaces several smaller ones and simplifies the hydraulics — fewer fittings, lower pressure drop.
• Weather-compensated control of large systems. Paired with the Termojet 411 (0–10V) actuator, the valve smoothly reduces supply temperature according to outdoor air temperature — fuel savings without pressure spikes.
• Mixed circuits with radiators and underfloor heating. The DN40 valve provides sufficient flow to feed several branches simultaneously.
• Manual balancing. Without an actuator, the valve is locked in any position by a handle — static temperature setting without automation.

Advantages of Termojet DN40

• CW617N brass body — corrosion resistance and manufacturing precision on par with leading European equivalents.
• Leakage below 0.1% Kvs — minimal losses in the closed position.
• Standard actuator mounting — installation of 405N/411 series actuators without additional adapters.
• EPDM seals — resistance to glycol heat-transfer fluids and elevated temperatures up to 110°C.
• Ball torque below 5 Nm — compatible with 6 Nm actuators with a comfortable torque margin.

Compatible Actuators

To automate the Termojet DN40 Kvs 25 valve, install an actuator with a torque of at least 6 Nm:

• Termojet 405N actuator (3-point, 230V) — the standard choice for boiler rooms with a 3-position controller output, smooth regulation of large circuits.
• Termojet 411 actuator (0–10V, 24V) — for weather-compensated automation, smart-home integration, and heat-pump systems.

Valve and Heat Pump

In large bivalent systems the heat pump provides the base heat supply and the boiler connects in peak mode. The DN40 three-way mixing valve paired with the 411 (0–10V) actuator maintains the optimum supply temperature for each heat source — without hydraulic shocks or unnecessary costs. More about integrated schemes — on the Termojet heat pumps website.

FAQ

What boiler capacity is DN40 suitable for?
Kvs 25 and DN40 are for systems of approximately 60–120 kW depending on the temperature curve and type of heat-transfer fluid. For smaller systems (up to 50 kW), consider DN25 or DN32; for larger ones — DN50.

Is the DN40 valve compatible with actuators from other manufacturers?
The valve has a standard actuator mounting. Check the 90° rotation angle, flange seat dimensions, and torque — it must be greater than the valve ball torque (below 5 Nm). The recommended Termojet 405N and 411 series actuators mount without adapters.