The boiler performs a combined task of heating sanitary water and domestic heating. It can only do one or the other, never both at the same time. This means that if the radiators heat up during the use of sanitary hot water, then there is a problem with the boiler’s diverter valve or alternatively with the sensors that handle the anti-freezing system.

Solving the Problem of Hot Radiators in Summer

To immediately resolve this inconvenience, while waiting for your trusted technician, you can close the radiators one by one.

The radiator has two valves:

• The lockshield: allows you to close the radiator or thermosiphon in such a way that a key is needed to open it
• The shut-off or thermostatic valve: can be used by hand and effectively closes the radiator/thermosiphon

Use the shut-off or thermostatic valve, turn it clockwise until it stops. Note that it is not recommended to keep this valve closed for more than a month to avoid the shaft from locking.

Diverter Valve in Boilers

The diverter valve in the boiler is usually responsible for this inconvenience, it will probably need to be replaced. However, it is important to ask whether the failure of this valve could be random or related to other problems such as:

• Dirt in the heating circuit: Dirt prevents the valve from completely closing the radiator line in the production of sanitary hot water. For this problem, it would be appropriate to ask the technician if it is necessary to flush the heating system.
• Too much limescale in the boiler: Only for storage boilers, it can happen that the high operating temperatures of the primary block the diverter valve. In this case, it would be necessary to descale the storage boiler tank.