# Heating Control (legacy)

> Symcon documentation · English · generated on 2026-11-09  
> Index: https://www.symcon.de/en/llms.txt

Source: https://www.symcon.de/en/service/documentation/module-reference/legacy/heating-control-legacy/

> **Warning:** This is a deprecated version. From version 5.0 onwards it is recommended to use the new [Heating Control](heating-control.md) version.

### Description

The heating module (legacy) is a two-point controller for regulating temperatures in living spaces. It compares the target value with the actual value and switches the configured transmit instances on or off directly. Alternatively, a handler script can be executed which takes care of switching.

### Settings

| Setting            | Description                                                                                                                                                                                                                                                            |
| ------------------ | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Source Variable    | Variable that contains the actual value.                                                                                                                                                                                                                               |
| Hysteresis         | Temperature difference between the switch-on and switch-off point; Example: T-Target = 20.0 degrees and hysteresis = 0.4; The actuator is switched on when dropping below 19.8 degrees and switched off when exceeding 20.2 degrees.                                   |
| SetBack            | Temperature in °C by which the target is lowered if one or more of the "SetBack Variables" are __TRUE__.                                                                                                                                                               |
| Transmit Devices   | Instances that are switched. For thermal actuators that are open when de-energized, "Invert" must be activated. The supported instances are listed below.                                                                                                              |
| Override Variables | Can be e.g. status variables of window contacts. When __TRUE__, the output of the controller remains off.                                                                                                                                                              |
| SetBack Variables  | Can be e.g. presence variables of motion or presence detectors. If no person is in a room, energy can be saved by lowering the temperature.                                                                                                                            |
| Resend Interval    | Interval in minutes in which the current state is sent again, in case a (radio) command was not processed correctly. With 0 nothing is resent.                                                                                                                         |
| Handler Script     | Expert setting: If a script is selected, the transmit instances are not switched directly. Instead, the script is executed on each switching operation. The necessary data is available in the [System Variables](../concepts/automations/php-scripts.md). |
| Test Center        | To check the function of the controller, a target temperature can be entered here. The actuator must then turn on or off as desired.                                                                                                                                   |

> **Note:** Scripts executed by the Heating Control (legacy) include these [System Variables](../concepts/automations/php-scripts.md)

| Status variables | Ident               | Description                                                                                               |
| ---------------- | ------------------- | --------------------------------------------------------------------------------------------------------- |
| Target Value     | TargetValueVariable | Contains the target temperature.                                                                          |
| Override         | OverrideVariable    | If __TRUE__, at least one override variable is also __TRUE__ (OR operation) and the actuator remains off. |
| SetBack          | SetBackVariable     | If __TRUE__, the setback is active.                                                                       |
| Heating          | HeatingVariable     | Reflects the output of the controller. Inverting the transmit instances has no effect on this variable.   |

The target value can also be set via [HC_TargetValue](heating-control.md).

### Supported transmit instances

Without a handler script, the following instances can be switched directly:

 * ALLNET
 * DMX
 * EnOcean RCM100 and Opus
 * FS20
 * HomeMatic
 * KNX EIS
 * LCN (output and relay)
 * ModBus
 * Siemens
 * xComfort switch and dimmer
 * Z-Wave

If an instance cannot be switched, a warning is written to the message log.

> **Warning:** Since the PC (controller) can fail at any time, a temperature limiter / safety shutdown must also be installed to prevent injury or damage.