None of the rooms of the house needs heat, all of the heating zones on the app are blue, but the boiler is still firing unnecessarily. Some combination boilers (made by companies like Vaillant and Worcester Bosch) have a setting where the boiler could be set to maintain hot water in the system for the taps. For example, this boiler can have two programs, one for heating and one for hot water built into the front of the boiler. The heating program needs to be left on 24/7 as this is being controlled by the Genius System via the thermostat terminals on the boiler. However, if the hot water timer is left on, it will cause the boiler to come on intermittently during the day because a thermostat in the small hot water cylinder in the back of the boiler is triggering the boiler to make more hot water. When this timer is turned off for the hot water the boiler will stop turning on intermittently to heat this water, but the boiler will still provide hot water on demand. Many boilers have an overrun feature whereby the boiler continues to run after the heat demand has been satisfied. This is to distribute the hot water around the system both to areas where the hot water may be needed and to reduce the temperature of the water in the boiler.
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