THETA heating controller FAQ

There are various ways to access THETA controls remotely:

1. Using a Modbus GLT module, many parameters of the THETA control system can be accessed via Modbus RTU. A full list is available on request.
2. With the heatapp! base T2B and the heatapp! app

From version 3.x onwards, THETA is compatible with heatapp! You can control THETA using the heatapp! app. You can find out more about THETA and heatapp! base T2B at heatapp! base T2B.

3. With the new software version 2.2.42973 of the heatapp! base T2B, you also gain the ability to access the heatapp! base remotely via Modbus, MQTT and Home Assistant. Please note that access is limited exclusively to the parameters listed below:

Outdoor temperature 1 Read

Outdoor temperature 2 Read

Room temperature 1 - n Read

Room setpoint temperature 1 – n Read / Write

Heating circuit flow temperature 1 – n Read

Heating circuit setpoint temperature 1 – n Read

Hot water actual temperature Read

Hot water setpoint temperature Read / Write

Energy generator flow temperature Read

Energy generator return temperature Read

Other THETA values cannot be transmitted via heatapp! base T2B to Modbus/MQTT/Home Assistant.

As development of the THETA was completed several years ago, no further enhancements are expected in this regard.

If you would like comprehensive integration into your existing Modbus system AND control via the app from anywhere, you can operate the heatapp! base T2B and the Modbus GLT module in parallel.

The connection diagram on the rear of the THETA is universal and only provides limited information about the control options. The same applies to prefabricated cable sets. Note the type designation on the type plate of the THETA controller, which indicates the possible functions of the controller as follows:

THETA+ = Controller version 3.x

N = standard housing (installation dimensions 138 x 92 mm)

2 = single-stage GEN with unmixed heating circuit

22 = two-stage GEN with unmixed heating circuit

3 = one mixer heating circuit

33 = two mixer heating circuits

B = domestic hot water

VV = variable outputs (solar, buffer, solids, etc.)

C = Communication

OT = OpenTherm

Example: THETA+ N2B = Controller version 3.x, standard housing (installation dimensions 138 x 92 mm), single-stage WEZ with unmixed heating circuit, domestic hot water

Summer switch-off only works in automatic operating mode

Summer switch-off acts on the outdoor temperature long-term value and not on the current outdoor temperature. The long-term value is influenced via system parameter 10 (building type). Setting "1" accelerates the mode of operation of the summer switch-off.

As a check, look at the calculated average value of the outside temperature in the info level to draw conclusions about the switching point of the summer switch-off. To do this, display the outside temperature in the info menu and press the rotary knob while doing so.

The average value is displayed at the bottom left while pressing.

The adaptation of the heating curve has been set to ON.

(See DC/MC parameter 05)

Possible error causes:

RED" was set as "reduced operation". (See DC/MC parameters REDUCED)

Frost protection is active

HEATING operating mode set

Use the information area on the THETA control to check the control status of the heat generator (burner):

Call up HEAT GENER. Temperature = display of the current GEN temperature on the right, press the rotary knob = display of the set temperature at the GEN, on the left.

Calling up the operating status of the GEN by continuing to rotate in the info area , HEAT GENER. OFF/ON.

The GEN does not switch OFF if at least the minimum boiler temperature + switching differential has not been reached after a passed request.

ATTENTION: THETA is not THETA, even if it looks like it.

The THETA control is used by various boiler manufacturers. The requirements of the respective boiler manufacturer were implemented in the devices. In some cases, there are major functional deviations in the products, which affect the operational safety of the boiler. It is therefore advisable to use a device from the corresponding boiler manufacturer. Therefore, contact the relevant boiler manufacturer or supplier.

The controller designations should be identical (old/new).

In the info area, the demand values are shown in the left-hand area of the display when the rotary knob is pressed during the actual temperature display.

A room unit (THETA-RS or THETA-RFF) is connected to the THETA heating controller, which automatically switches to separate operating mode. In separate operating mode, it is no longer possible to set the operating mode to SUMMER. When using THETA-RS (space station), it is possible to switch back to common operating mode. Here the procedure is as follows:

Enter the specialist code on the THETA control (see specialist instructions).

Set the "BUS RIGHT" in the menu "Data bus" to 1.

Now set the "Operating mode" parameter in the "System" menu to 1.

Now the operating mode SUMMER is available again.

ATTENTION: If a THETA-RFF is used in the system, this is not possible.

There are two types of error messages:

System errors: These are errors that influence the control behaviour and are not corrected automatically. These are usually connection errors (e.g. sensor defects). These errors are displayed almost immediately.

Logical errors: These errors have no effect on the control behaviour of the control. The display is purely informative. These are errors that refer to temperature specifications that were not fulfilled by the control system. Setpoint temperatures are not reached. The error is triggered by a hydraulic problem. (No heat transport due to defective pump/valve or mixing valve) The display of logical errors can be switched off in the System menu.

The error message is only displayed in the basic display and this alternates with the basic display. The error code is shown in the bottom right of the display.

XX-X = Sensor position (is also shown in text form in the top line).

XX-0 = "0" stands for interruption

XX-1 = "1" stands for short circuit

A list of possible error messages can be found in the specialist manual.

If the correct specialist code has been set, the display will show "INSTALLER OK" for approx. 2s.

However, the display will now return to the display before the code was entered!

However, all menus and parameters are now enabled and available for the specialist area according to the specialist instructions.

If the wrong code was set, the display shows "CODE WRONG" for approx. 2s. Check the setting and contact our technical support if necessary.

For the controllers that do not have their own outdoor sensor (OS) connected, perform an "AUTO SET". In this way, the requested OS is logged off. However, a value from the OS connected in the system is still transmitted via the bus.

There are two possibilities here:

1. The Controller is switched to de-energised. The rotary knob is now pressed and held down! Now the mains is switched on again while the rotary knob is pressed. All segments are shown in the THETA display. When this segment test is finished, the rotary knob can be released again. The control now executes the AUTO SET function.

2. Set the system parameter 14 to "ON" and then switch the Controller off briefly. After switching on again, the AUTO SET function is executed.

The auto set function recognises the following sensors:

Outdoor sensor

Boiler sensor

Hot water tank sensor

Flow sensor 1

Flow sensor 2

The Rapido controllers are compatible with heatapp! However, there is one special feature: Rapido controllers of hardware generation E correspond to EbV Theta controller version 2.3 (hardware D) and are therefore only compatible with heatapp! to a limited extent. From hardware version F onwards, Rapido controllers are also fully compatible.

Emission measurement is not controller-independent and must be started at each controller. If a stage delay is activated, the second stage is only switched on after the delay time has elapsed.