A heater (1) uses an intermittently working burner (1') that is automatically switched on when the temperature at a temperature sensor (6) falls below a switching-on temperature (TE) and is switched off when the temperature reaches a switching-off temperature (TA). For the burner (1') to remain switched on during a certain minimum time even when heat demand is low, the switching-on temperature is automatically lowered when the last working period of the burner was shorter than the minimum time.
