Thermostatic mixing unit Termojet for underfloor heating manifold TJ-MU-40A

The Termojet TJ-MU-40А pump-mixing unit is a powerful ready-made solution for connecting large or multi-zone underfloor heating systems to a boiler or heat pump. The built-in thermostatic three-way valve of the TMV series automatically maintains the supply temperature within an extended range of 25–55°C without power supply or external sensors. The unit ensures stable circulation of the heat transfer fluid and protects the floor circuits from overheating — regardless of the boiler's temperature mode.

Technical specifications

Operating principle: the TMV valve

The key element of the unit is the thermostatic three-way mixing valve TMV with a thermo-sensitive element built directly into the valve body. The thermal element continuously responds to the temperature of the mixed heat transfer fluid at the outlet and mechanically moves the spool: it blends the cooled return flow into the hot supply or increases the share of hot fluid — until the supply temperature to the underfloor heating circuit stabilizes within the set range of 25–55°C.

Control is completely passive: no external sensor, no electronics, no wiring to the unit. The thermo-sensitive element acts inside the valve — this distinguishes the TMV valve from solutions with remote sensors or capillary tubes. More about the thermostatic valves of the TMV series — in the Termojet valve catalog.

Application scenarios

• Large house or cottage. The TJ-MU-40А is designed for higher thermal loads than the compact TJ-MU-10B model. It is suitable for houses with an extensive underfloor heating system — several rooms, large circuit areas.
• Boiler + underfloor heating. The boiler supplies 70–80°C — the unit lowers the temperature to a safe 25–55°C for the floor circuit. The TMV valve blends the return flow automatically, without operator involvement.
• Extended temperature range. The upper limit of 55°C (versus 43°C in the TJ-MU-10B) allows the unit to be used in systems with a higher required heat flow or with less insulated buildings, where the floor needs a higher supply temperature.
• Combination with a multi-circuit manifold. Together with a manifold with flow meters for 10 outlets, the TJ-MU-40А unit forms a complete control unit for a large floor heating system.
• Bivalent scheme. When the heat pump operates as the main source and the boiler as a backup, the unit isolates the floor circuit from temperature surges when switching between heat sources.

Advantages of the TJ-MU-40А unit

• Extended range of 25–55°C. A higher upper temperature limit provides greater flexibility in design — suitable for facilities with different heat flow requirements.
• No power supply required. The TMV valve regulates the temperature solely through the thermal energy of the heat transfer fluid. The unit works even during a power outage.
• Ready-made assembly of increased power. The pump and the TMV valve are combined into a single unit for more powerful systems — reducing installation time and the number of connections.
• Floor protection from overheating. The TMV valve physically does not let through heat transfer fluid hotter than the upper limit of the range — PE-RT pipes, screed and flooring are reliably protected.
• Reliability without complex automation. The absence of electronic components in the valve minimizes the probability of failure and requires no setup or programming.

Underfloor heating and the heat pump

A heat pump operates efficiently at a supply temperature of 35–50°C — it is precisely within this window that the COP coefficient of performance reaches 4–5. The range of the TMV valve of the TJ-MU-40А unit (25–55°C) fully covers the operating zone of the heat pump, so the floor heating system receives heat transfer fluid of optimal temperature without the risk of overheating. When the temperature rises in bivalent mode (boiler + heat pump), the valve automatically limits the supply temperature to a safe limit. About comprehensive solutions for floor heating from a heat pump — on the Termojet heat pumps website.

Frequently asked questions

How does the TJ-MU-40А differ from the TJ-MU-10B?
The TJ-MU-40А is a more powerful model with an extended temperature range of the TMV valve: 25–55°C versus 20–43°C in the TJ-MU-10B. The TJ-MU-40А unit is designed for larger underfloor heating systems — large houses, cottages, facilities with an extensive network of circuits. The TJ-MU-10B is a more compact option for apartments and small houses. Choose based on the area of the floor circuit and the required thermal load.

Is the unit safe during a power outage?
Yes. The TMV valve does not require power supply — it regulates the temperature mechanically, through the reaction of the thermo-sensitive element to the temperature of the heat transfer fluid. During a power outage the pump stops, but the valve remains in its current position and prevents the circuit from overheating when circulation resumes.