Thermostatic mixing unit Termojet for underfloor heating manifold TJ-MU-10B

The pump-mixing unit Termojet TJ-MU-10B is a compact, ready-to-install solution for connecting an underfloor heating circuit to a boiler or heat pump. The built-in thermostatic three-way valve of the TMV series automatically maintains the supply temperature in the range of 20–43°C without any electrical power. The unit ensures circulation of the heat-transfer fluid through the floor loops and protects the screed from overheating — completely passively, without controllers or sensors.

Technical Specifications

Operating Principle: TMV Valve

The heart of the unit is the thermostatic three-way mixing valve TMV with a built-in thermosensitive element. It continuously monitors the outlet temperature of the heat-transfer fluid and automatically blends cooled return flow with the hot supply from the boiler — until the underfloor heating circuit temperature reaches the set limit in the range of 20–43°C.

The process is entirely passive: no electrical power, no external sensors or capillary tubes. The thermosensitive element expands or contracts directly inside the valve body — mechanically moving the spool, changing the ratio of hot and return flows. Learn more about TMV thermostatic valves in the Termojet valve catalogue.

Application Scenarios

• Boiler + underfloor heating. The boiler delivers 70–80°C — the floor needs 30–40°C. The TJ-MU-10B unit solves this automatically: the TMV valve blends in the return flow and reduces the temperature to a safe level. An essential component when connecting an underfloor circuit to a high-temperature boiler.
• Compact installation. The TJ-MU-10B is designed for smaller systems — an apartment, a small house, a few rooms. The compact dimensions simplify installation in a manifold cabinet or technical compartment.
• Zone heating. In combination with the 6-outlet manifold with flow meters, the unit provides a separate temperature regime for the underfloor circuit within the overall house heating system.
• Renovation. Replaces an outdated or missing mixing solution without re-routing pipes — installed inline in the existing supply.

Advantages of the TJ-MU-10B Unit

• No electrical power. The TMV valve operates solely on the thermal energy of the heat-transfer fluid — no dependence on the electrical grid, no wiring to the unit required.
• Ready assembly. The pump and valve are assembled into a single compact unit — minimum installation connections, minimum time expenditure.
• Screed protection. The TMV valve will not allow heat-transfer fluid hotter than 43°C into the underfloor circuit — the screed, PE-RT pipes and floor covering are protected from overheating regardless of the boiler temperature.
• Easy maintenance. The absence of electronic components reduces the probability of failure and simplifies diagnostics.

Underfloor Heating and Heat Pump

A heat pump generates heat-transfer fluid at 30–50°C — exactly the range at which underfloor heating operates most efficiently. With a low-temperature source, the TMV valve of the TJ-MU-10B unit does not restrict flow: if the supply temperature is already within 20–43°C, the valve is fully open and creates no additional hydraulic resistance. The unit remains useful for hydraulic separation of circuits even when a heat pump is the primary heat source. For comprehensive underfloor heating schemes powered by a heat pump, visit the Termojet heat pumps website.

Frequently Asked Questions

Is a mixing unit needed with a heat pump?
If the heat pump is already configured for a low supply temperature (35–45°C) and there is no need for hydraulic circuit isolation — the unit may not be mandatory. However, in a bivalent scheme (heat pump + boiler) or when multiple circuits with different temperatures are present, a unit with a TMV valve simplifies hydraulics and eliminates the risk of floor overheating from the boiler during transition modes.

What is the difference between TJ-MU-10B and TJ-MU-40A?
TJ-MU-10B is a compact unit for smaller systems, TMV valve temperature range: 20–43°C. TJ-MU-40A is a more powerful variant with an extended range of 25–55°C, aimed at larger installations with higher capacity. The choice depends on the area of the underfloor circuit and the required thermal load.

The circulation pump is not included in the scope of delivery — it is selected separately.