Why is a radiator not heating?
Distinguish a single-radiator problem from a building-wide issue.
Identify the affected area
Is the problem limited to one radiator, one apartment, a riser or the entire building? This helps assess valves, trapped air, circulation and central heat generation.
Safe initial checks
Record room temperature, valve setting and when the problem began. Do not interfere with the plant room, pressurised pipework or gas equipment.
A lasting solution
For recurring differences in heating, review hydraulic balance, pump operating point, filters and controls together. Not every problem is solved by flushing radiators or installing a larger pump.