---
title: "Create a Chart’nX water meter group: primary and secondary meters"
description: "Create a water group in Chart’nX: real or virtual primary, KNX or Modbus secondary meters, units, group total and display checkboxes for each meter."
canonical: https://wiki.can-nx.com/en/guides/chart-water-groups/
language: en
product: Chart’nX
audience:
  - administrateur
  - installateur
context: "Chart’nX: water dashboard generator, Sub-meters section and its groups"
---

# Create a Chart’nX water meter group: primary and secondary meters

Context: Chart’nX: water dashboard generator, Sub-meters section and its groups

In a Chart’nX water dashboard, a group brings together a primary meter and its secondary meters, KNX or Modbus. The primary is either a real measurement or the virtual sum of its secondaries. Each group forms one layer of the distribution pie chart.

Intended for administrators and installers.

## Before you start

- The water dashboard is open with **Configure** and its [general information](https://wiki.can-nx.com/en/guides/chart-water-general/) is filled in.
- The unit and the KNX address or Modbus configuration of each measurement are known.

## Create the group and its primary

1. In **Sub-meters**, click **+ New group**. A group card appears with **1 primary** and the number of secondaries.
2. In its **Primary** card, fill in **Meter name**. Fictitious example: “Water floor 1”.
3. Choose **Real** if you have a dedicated measurement for the primary, or **Virtual (∑ secondaries)** if the primary must be the sum of the secondaries of this group.
4. For a **Real** primary, choose **Protocol**, **Index** or **Not indexed**, then the KNX **Group address** or the **Modbus Configuration**, the **Meter unit of measurement** and the **Custom Factor**. Use the known parameters of the measurement, as for [the total water meter](https://wiki.can-nx.com/en/guides/chart-water-general/). For a custom calculation, follow [Compose a water calculation](https://wiki.can-nx.com/en/guides/chart-water-operations/).
5. For a **Virtual (∑ secondaries)** primary, the protocol and address fields are replaced by the sum indication. Keep a name and choose its unit. Then add at least one secondary, otherwise the group cannot be validated.

Switching from **Real** to **Virtual (∑ secondaries)** changes the meaning of the primary. To return to **Real**, check all its parameters again, especially the address or the Modbus configuration: an old setting may no longer match the installation.

## Add the secondary meters

1. In the group, click the **+ Add secondary meter** card.
2. Give the added meter a name, then fill in its protocol, its measurement, its unit and its factor. Repeat for the other measurements.
3. For several existing Modbus configurations, use **Import modbus** in the header of this same group, according to [the import procedure](https://wiki.can-nx.com/en/guides/chart-modbus-import/).
4. Under a virtual primary, each secondary has a **Count in the group total** box, checked initially. Uncheck it if this meter is already measured by another secondary (nested meter). The **Include in the total pie chart** box is then unchecked and locked.

## Set the units and the display

1. For each meter of the group, primary included, choose the unit actually received: **Liter (L)**, **Kiloliter (kL)** or **Cubic meter (m³)**. A group can mix these units: Chart’nX converts the values to liters before combining them.
2. Keep the **Custom Factor** for the metering ratio, for example 10 units per pulse, not for converting a unit. Ask the installer if in doubt.
3. Add the useful presence overlays with **+ Add overlay**, as for the total meter.
4. On each secondary, check **Display**: **Show in chart** and **Include in the total pie chart**. Both boxes are initially checked; they control the display without removing the card from the form.

## Check the result

[Save the dashboard](https://wiki.can-nx.com/en/guides/chart-save/), then open it over a period in which you expect data: check the composition of the group and compare the primary’s value with those of its secondaries. You can then [choose the group’s color and the order of the cards](https://wiki.can-nx.com/en/guides/chart-water-layout/).

## Troubleshooting

- “a virtual primary needs at least one secondary meter”: add a measured secondary, or return to a real primary if that is indeed the intended installation.
- The sum of the virtual primary looks wrong: check the **Count in the group total** box of each secondary.
- For an inconsistent volume or a refused save, follow [the water dashboard troubleshooting](https://wiki.can-nx.com/en/guides/chart-water-help/).

If the expected composition remains uncertain or if validation is blocked after these checks, contact support@can-nx.com with the name of the primary, the message and the checks made.