Why does the radiator heat less at the top?

When you have an electric radiator at home, you often ask yourself why the top of the radiator is slightly cooler than the rest. The answer here is the air cushion. The key element is the thermal expansion of the heating medium. As the temperature of the medium increases, its volume increases, which leads to an increase in pressure. Air, as a gas, is compressible and compensates for the increase in this volume.

TERMA recommendation: The air cushion recommended by TERMA, measuring 8% of the radiator's volume, guarantees that the pressure inside the radiator will not increase to dangerous values, even with irregular operation of the heater resulting in a large increase in temperature, regardless of the causes of the anomaly.

Thermal expansion of the heating medium: In an electric radiator powered by a heating element, the thermal expansion of the heating medium is important. As the temperature increases, the particles of the medium move away from each other, which leads to an increase in volume. This increasing volume in a tightly closed tank can lead to a dangerous increase in pressure inside the radiator.

Proper provision of space: To prevent damage caused by excessive pressure increase inside the radiator, it is necessary to leave free space. Lack of air cushion or too little of it exposes both the radiator and the heating element to damage.

Maintaining proper operation: In a central heating radiator with a heating element, similar physical phenomena occur. The value of the heating medium volume also increases, but in this case the task of compensating the pressure increase must be taken over by the central heating installation, or more precisely - the compensation (expansion) vessel.

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