Vaillant Heat Pump Controls: Part 4: The App

Friends, just as I finished the previous article about Vaillant Heat Pump Controls, Vaillant introduced a new way to set the heat curve using their My Vaillant App. I thus feel obliged to say something about this. Fortunately, there doesn’t seem to be much to say.

Sorry: I’ll get back to more interesting topics soon.

Previously

Previously I looked at what why heating curves are curved, how they work, and how to adjust them using the Vaillant SensoComfort controller.

Click on image for a larger version. The Vaillant SensoComfort Controller.

At first sight I thought the App gave a more detailed way to specify the heat curve, but in fact it simply gives another way to adjust exactly the same heat curves.

To adjust the heat curves using the App, from the App Home Screen:

• Select the “Settings” Icon: a cog wheel.
• The Select “Control”
• Then Select “Heat Curve Settings”: This will display the current heat curve.
• Then Select “Heating Curve (Expert)”

Click on image for a larger version. Successive screens in the app showing how to navigate to heat curve settings page.

With good fortune you should arrive at a page that looks similar to this:

Click on image for a larger version.

• The Flow Temperature (°C) is shown on the vertical axis
• The Outside Temperature (°C) is shown on the horizontal axis.
• The selected heating curve is displayed with values of flow temperature for outside temperatures of 20 °C, 10 °C, 0 °C, -10 °C and -20 °C and an internal target temperature of 21 °C.

The key thing to understand is that the setting “Steepness of curve:” is just the same as the Heat Curve Label discussed in the previous articles. You can adjust it using the + and – signs in steps of 0.05. As you adjust it, the graph changes.

When you navigate back to the Home Screen, the App will check that you want to save changes, and if you confirm, then the Heating Curve will be updated.

This can be checked by navigating to the relevant Screen on the SensoComfort (Settings:Installer Level:Code 00:Installation Config: Circuit 1). You should then see the modified setting.

Note: On my system the setting does not work both ways. Adjusting the heating curve on the SensoComfort does not update the setting in the App. 

If you click on ℹ️LEARN MORE icon on the graph, the App displays the following generally helpful text.

Basic terms

The heating curve shows the flow temperature over the outside temperature. At higher outside temperatures the flow temperature is reduced for a better efficiency. The flow temperature also depends on the room temperature setpoint and is shown here for 21 °C. A higher room temperature results in a higher flow temperature.

The ideal configuration depends on your individual system. For example, factors like the heating surface and the building’s insulation need to be considered. Below you will find some guide values.

• Steepness ~0.4 for a well-insulated house with underfloor heating (Tmin 15°C)
• •Steepness ~0.6 for an older house with underfloor heating (Tmin 20°C)
• Steepness ~1.1 for a well-insulated house with radiator heating (Tmin 25°C)
• Steepness ~1.5 for an older house with radiator heating (Tmin 30°C)

If your system does not reach the desired room temperature at low outside temperatures you should increase the steepness of the curve.

If your system does not reach the desired room temperature only at moderate outside temperatures, please increase the minimal flow temperature.

Please note: changing your heating curve configuration might impact your comfort or the system efficiency. In some systems the heating curve is not used. In this menu, the heating curve is only shown for your main heating circuit. Please contact your installer if you would like to configure multiple heating circuits.

Normally, the heating curve will be set by an installer who will have a good idea of an appropriate setting from experience. If one has no idea where to start then the text above may be helpful. Alternatively, one can use the spreadsheet in the previous article to calculate the heating curve label (aka Steepness) from the calculated flow temperature at the design condition.

Heat Curve Labels and Steepness

One question I had hoped might be resolved was the origin of the numbering system for the heat curves. The new name hints that the name might relate to the steepness of the heating curve at some particular condition.

So I created a table of steepnesses and looked for some sort of correlation between the heat curve name, and the actual slope of the curve at different outdoor temperatures.

Click on image for a larger version.

In the table above we can see that the steepness does generally increase as the heating curve increases, but it is difficult to see a justification for the naming of the heat curve based on these slopes. I have coloured in purple (or pink?) the outside temperatures at which the steepness of the curves is equal to the label of the heat curve. It’s clear that this does not happen at a consistent temperature.

So the mystery of the heat-curve labelling convention has not been solved.

Summary

The updated App gives access to the heating curve in a more straightforward and less arcane form than previously. This is a good thing and represents progress in an otherwise shaky and chaotic universe.