Four-way mixing valve Termojet, DN32, kvs-18 female thread

The Termojet DN32 four-way rotary mixing valve is the key protective element for solid-fuel (wood or pellet) or gas boilers against condensation corrosion. Internal thread Rp 1¼", flow coefficient Kvs 18 m³/h, working pressure PN 10 bar, temperature range –10…+110°C. Body — brass CW617N, EPDM seals. The valve simultaneously solves two tasks: it blends hot water from the boiler into the return pipeline and regulates the supply temperature to the heating circuit.

Technical Specifications

Operating Principle

The valve has four ports: K+ — supply from boiler, K– — return to boiler, H+ — supply to heating circuit, H– — return from circuit. When the disc rotates 90° on an actuator signal, two flows are regulated simultaneously. When cold return water arrives from the circuit, the valve blends part of the hot supply from the boiler into pipeline K–, raising the return temperature before it enters the combustion chamber. At the same time, the supply temperature to circuit H+ is reduced by mixing hot water with the return.

Why this is critical for solid-fuel boilers: when the return temperature falls below the dew point (60–65°C for wood, 55°C for gas), moisture condenses in the combustion chamber — causing corrosion, resin deposits on the walls, and sharply reduced boiler service life. The four-way valve ensures the boiler always receives return water above the critical threshold.

Applications

• Solid-fuel boiler (wood, pellets, briquettes). Protection against condensate and resin deposits during system warm-up or partial load — the most common and most important application of the 4-way valve.
• Non-condensing gas boiler. Maintaining the return temperature above 55°C extends the heat exchanger service life and prevents deposits in the combustion chamber.
• Boiler + thermal storage (buffer tank). The valve controls the flow between the boiler, buffer, and heating circuit — the boiler does not "see" cold water even when operating with a large buffer tank.
• Bivalent system (heat pump + boiler). The valve manages the priority and mixing of two heat sources — the heat pump as primary, the boiler as backup during peak loads.
• Stove with water circuit. Protection against thermal shock during ignition — the valve prevents cold water from the system from entering the heated stove.

Advantages of Termojet DN32

• Brass body CW617N — corrosion resistance, manufacturing precision on par with leading European equivalents.
• Kvs 18 m³/h — optimal for boiler rooms rated 30–60 kW, matching standard flow rates in residential and small commercial systems.
• Disc torque under 3 Nm — compatible with 6 Nm actuators with double the torque reserve.
• EPDM seals — resistant to glycol heat transfer fluids and elevated temperatures.
• Leakage under 0.1% — minimal heat losses in the end positions of the disc.

Compatible Actuators

To automate boiler protection, install one of the Termojet actuators (valve disc torque — under 3 Nm; all actuators listed below provide double the torque reserve):

• Termojet 405N electric actuator (3-point, 230V) — standard choice for boiler rooms with a 3-position controller output, smooth modulation.
• Termojet 411 electric actuator (0–10V, 24V) — for weather-compensated control and integration with a smart home or heat pump.
• Termojet 413 actuator-controller — autonomous actuator with built-in temperature sensor and controller: maintains the set return temperature without a separate controller.

Valve and Heat Pump

In bivalent systems where the heat pump is the primary heat source and the boiler is backup, the Termojet DN32 4-way valve manages switching and mixing between the two sources. The valve ensures that when the boiler is connected it does not receive cold return water from a system where the temperature has dropped below the safe threshold. For more about bivalent schemes, visit the Termojet heat pumps website.

Frequently Asked Questions

Why use a 4-way valve when a 3-way valve exists?
A 3-way valve either mixes the supply temperature to the circuit or protects the boiler return — but not both simultaneously. A 4-way valve solves both tasks in a single body: it blends hot water into the return pipeline (boiler protection) and simultaneously regulates the supply temperature to the circuit. For solid-fuel boilers this is a fundamental difference — especially during the transitional period when warming up a cold system.

Which actuator to choose for the Termojet DN32 4-way valve?
Valve disc torque — under 3 Nm. Compatible actuators: 405N (3-point, 230V), 411 (0–10V, 24V) and 413 (built-in sensor and controller). For weather-compensated control — 411; for autonomous operation without an external controller — 413; for simple boiler room schemes — 405N.