Boiler runs but radiators remain cold or only lukewarm

Safety first: Radiators and pipes may be hot. Use gloves and take care when bleeding radiators.

Steps to check:

• Check boiler temperature: Ensure the flow temperature setpoint on the Kospel boiler is high enough for space heating (e.g., 60–70°C depending on system design).
• Bleed radiators: Starting with the highest radiators, use a bleed key to release trapped air until water flows steadily.
• Verify valves: Confirm that all radiator valves and any zone valves are fully open.
• Assess pump performance: Feel the flow and return pipes near the boiler. A very small temperature difference may indicate poor circulation. The pump may need to be set to a higher speed or replaced.

When to call a technician: If circulation remains poor after bleeding and valve checks, a heating engineer should evaluate pump sizing and system balancing.