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We have a modern, thermally efficient house. Last year we replaced our boiler with a Vaillant ecoTec model. Due to compatibility issues with our existing Honeywell room stat we had to replace that too, so we went for Vaillant's vSmart control system.
According to the Vaillant advertising (such as this video) the vSmart is supposed to modulate the heating flow temperature when the room stat reaches the setpoint. By running at a lower flow temperature the boiler is more efficient and its service life is theoretically extended because thermal shock is reduced.
However, our experience is quite different. The boiler runs at a very high flow temperature (70°C or above) and keeps running at that temperature even when the room stat has reached the setpoint. The boiler then switches off several minutes later and the heating overshoots by a good 0.8 - 1.0°C. It then doesn't come on for several hours while the house cools down.
This morning, for example, the temperature outside was 2.6°C, the vSmart was requesting a flow temperature of 83°C (D.009 eBus target temperature), and the boiler was maintaining a flow temperature of 75°C (set as a maximum in the boiler settings) with a heating return flow temperature of 65°C. Over the past two weeks, the highest D.009 temperature we've seen is 85°C and the lowest is 70°C. This seems very high. It also results in radiators that are almost too hot to touch and uneven heat distribution in the rooms.
The vSmart app shows the system using the "Advanced" algorithm, and it has set its own heating curve to just 0.7.
The screenshot below illustrates the fluctuations we're experiencing - nothing like the graph in the linked video.
It looks to us as though the vSmart isn't doing what it's supposed to do. Do you think the vSmart is faulty, or are there some settings (either on the vSmart app or the boiler itself) that we need to check?
According to the Vaillant advertising (such as this video) the vSmart is supposed to modulate the heating flow temperature when the room stat reaches the setpoint. By running at a lower flow temperature the boiler is more efficient and its service life is theoretically extended because thermal shock is reduced.
However, our experience is quite different. The boiler runs at a very high flow temperature (70°C or above) and keeps running at that temperature even when the room stat has reached the setpoint. The boiler then switches off several minutes later and the heating overshoots by a good 0.8 - 1.0°C. It then doesn't come on for several hours while the house cools down.
This morning, for example, the temperature outside was 2.6°C, the vSmart was requesting a flow temperature of 83°C (D.009 eBus target temperature), and the boiler was maintaining a flow temperature of 75°C (set as a maximum in the boiler settings) with a heating return flow temperature of 65°C. Over the past two weeks, the highest D.009 temperature we've seen is 85°C and the lowest is 70°C. This seems very high. It also results in radiators that are almost too hot to touch and uneven heat distribution in the rooms.
The vSmart app shows the system using the "Advanced" algorithm, and it has set its own heating curve to just 0.7.
The screenshot below illustrates the fluctuations we're experiencing - nothing like the graph in the linked video.
It looks to us as though the vSmart isn't doing what it's supposed to do. Do you think the vSmart is faulty, or are there some settings (either on the vSmart app or the boiler itself) that we need to check?