3.6HVAC

The HVAC object is a compact climate tile. It shows the room's current temperature and the setpoint, and tapping it opens a popup to change the setpoint, switch the unit on or off, and pick a mode and fan speed. The gateway can also regulate the unit automatically around the setpoint.

#When to use it

• A room thermostat or fan-coil controller on KNX that exposes separate group objects for on/off, setpoint, mode and fan speed.
• Systems where the actuator expects the gateway to decide when to switch on and off (see Enable HVAC and Hysteresis below).

For Modbus air conditioners with their own panel, use the AC Panel instead.

#Properties

Label, Text style, Access control and Position and size work as described on Common properties. The HVAC object draws its own tile, so its On and Off images, Rotation, Mirror and Image Fitting have no effect in the apps.

#KNX addresses

#Mode and fan values

Actuators use different numbers for the same mode, so you enter the number each mode uses. The popup shows one button for each value that is filled in.

#Regulation

#How it behaves in the apps

The tile. The HVAC object is drawn as a tile, not an icon.

The tile shows the label with an on/off switch you can flip without opening the popup, the temperature in °C, and Set and Fan chips. The Veltnova client refreshes the tile every 5 seconds and never draws it smaller than 220 x 150.

The temperature comes from the Actual Temperature Feedback Group. The setpoint comes from the Setpoint Feedback Group, or the Setpoint Group when there is no feedback address. Values show as -- until a telegram has been seen.

The popup. Tapping the tile opens a popup with:

• the current temperature;
• a setpoint slider from 16 to 30 degrees in steps of 0.5, with - and + buttons. Each change is written to the Setpoint Group as DPT 9.001. If no setpoint is known yet the slider starts at 24;
• ON and OFF buttons that write to the ON/OFF Group Address;
• a Mode row (Auto, Cool, Heat, Dry, Fan) that writes the matching value to the Mode Group;
• a Fan Speed row (Auto, Min, Middle, Max) that writes the matching value to the Fan Speed Group.

A row is hidden when none of its values is set. The active button follows the Mode Feedback Group and Fan Speed Feedback Group.

Automatic regulation. Once a second the gateway looks at every HVAC object that has Enable HVAC on. It needs a known room temperature and a known setpoint. It adds the Setpoint Offset to the setpoint to get the target, and uses half the Hysteresis on either side of it.

• In Cool mode (and in Auto, or any mode value it does not recognise) it switches the unit on when the temperature rises above the target plus half the hysteresis, and off when it falls below the target minus half the hysteresis.
• In Heat mode it does the opposite. Heat is ignored when System Type is Cooling Only.
• In Dry and Fan modes it does nothing.
• Inside the dead band it holds the current state, and it only writes when its decision changes.
• With Cooling Only and Change Mode to Fan Only, reaching the setpoint writes ON and then the Fan mode value instead of OFF.

#Example

A fan-coil in a bedroom, cooling only.

With a setpoint of 24 and no offset, the gateway switches the unit on above 24.25 and sends fan-only below 23.75.

#Tips and common problems

• Temperature or setpoint shows --. No telegram has been seen on that address yet. Check the address, and that the actuator answers read requests so the gateway can read it after a deploy.
• The unit is switching on and off all the time. Raise the Hysteresis. A very small band follows every tiny temperature change.
• The unit does not respond to modes. The numbers under Value - ... Mode must match what your actuator expects. Check the manufacturer's group object description.
• Something other than the app is regulating. If the thermostat or actuator already regulates itself, set Enable HVAC to Off so the gateway does not fight it.
• System Type changed in other rooms. It is a project-wide setting, by design.

#See also

• Common properties
• AC Panel
• Analog Value
• KNX basics for installers