The buffer tank is hot but the fan coils or underfloor heating are not performing: a complete check

When the buffer tank is at the correct temperature but the spaces are not heating up, the problem is usually in the secondary circuit.

1. Secondary circulator

Check if it is operating and providing the required flow rate.

2. Valves and zones

Check solenoid valves, actuators, and whether the branches are actually open.

3. Mixing

Excessive return recirculation in the hydraulic separator may reduce the temperature delivered to the terminal units.

4. Filters and air

Clogged filters or air trapped in the circuit can significantly reduce the flow rate.

5. Temperatures

Measure the supply and return temperatures at the buffer tank and at the terminal units to identify where the actual efficiency is being lost.