Very small supply-return ΔT: when is it an indication of a problem

A very small ΔT can indicate high water flow, low load, or insufficient heat transfer to the building.

Possible causes

Excessively high circulator speed, bypass, open hydraulic crossover, or low active thermal load.

It is not always a malfunction

In inverter operation with low load, a small ΔT can be normal.

Correct assessment

Thermal power, flow rate, and terminal unit status should be examined simultaneously.