Bosch Control Key K20 RF Radio Frequency Receiver

The Bosch Control-Key K20 RF 7738113610 radio frequency receiver is a wireless communication module designed to connect compatible Bosch/Junkers boilers with the EasyControl CT200 control system. Thanks to radio frequency communication, it allows data to be transmitted between the boiler and the controller without the need to install a communication cable between both units, making installation cleaner and more flexible.

Reference 7738113610, technically identified by Bosch as K20 RF / EC-CT, operates with the EMS 2 communication protocol and uses a radio band of 868.3 to 869.5 MHz. It is specifically designed for boilers equipped with a slot or port compatible with the Control-Key module, so compatibility should always be checked with the exact model of the heat generator.

Wireless communication between boiler and EasyControl CT200

The main function of the Control-Key K20 RF is to establish radio communication between a compatible boiler and the Bosch EasyControl CT200 smart thermostat.

This solution makes it possible to avoid the communication cable between the controller located in the home and the boiler, providing greater freedom to choose the thermostat location within the coverage limits and installation conditions specified by Bosch.

The module acts as the system communication interface and not as an independent thermostat. To provide room temperature control, it must be used together with a compatible controller, such as the EasyControl CT200.

Designed for compatible Bosch and Junkers boilers

The K20 RF is intended for certain Bosch/Junkers heat generators prepared to use a Control-Key and EMS 2 communication.

Within the manufacturer’s current documentation, its use is contemplated in configurations with different Bosch Condens boilers and compatible Junkers models. Among the families cited by Bosch in regulation documentation are, depending on the market and version:

• Bosch Condens 2300i W.
• Bosch Condens 5300i W.
• Bosch Condens 5300i WT.
• Bosch Condens 5300i WM.
• Bosch Condens 5700i W.
• Bosch Condens 5700i WT.
• Selected Junkers Cerapur boilers.
• Other units equipped with a compatible Control-Key port.

The presence of EMS communication alone does not guarantee compatibility. Before purchasing or installing the K20 RF, it must be confirmed that the specific boiler has the housing and compatible electronics indicated by Bosch.

Compatible with Bosch EasyControl CT200

The Bosch EasyControl CT200 is a connected controller for heating systems that allows temperature and system scheduling to be managed.

The Control-Key K20 RF enables wireless communication between the CT200 and the compatible boiler, eliminating the need for a wired bus connection between both points in the configurations supported by the manufacturer.

868 MHz radio frequency communication

The K20 RF uses wireless communication in the European band of:

• RF frequency: 868.3-869.5 MHz.
• Maximum radio power: 10 dBm.

This band is intended for short-range wireless communications and allows the link to be established between compatible components of the heating system.

The effective communication distance depends on the conditions of each building, including walls, metal structures, room layout, interference, and device placement.

EMS 2 bus communication

The communication interface with the boiler uses Bosch’s EMS 2 system.

EMS 2 enables digital information exchange between the different compatible control and heat generation components. Thanks to this communication, the controller can interact with the boiler electronics in a more complete way than a simple on/off contact.

Integrated installation in compatible boilers

In Bosch units prepared for this solution, the Control-Key K20 RF can be installed in the specific housing provided in the boiler itself.

This integration offers several advantages:

• Reduces external wiring.
• Avoids taking up additional space next to the boiler in configurations with integrated housing.
• Maintains a visually clean installation.
• Facilitates connection with the generator’s electronic system.
• Allows wireless communication with the compatible controller.

Installation must be carried out following the instructions for the specific boiler model and the Control-Key.

12 to 23 V DC power supply

The technical documentation for the K20 RF specifies the following power supply characteristics:

• Supply voltage: 12-23 V DC.
• Maximum consumption: 1 W.

The module is designed to receive the corresponding power within a compatible Bosch installation. It must not be connected directly to a power supply other than the one specified, except through components and accessories expressly provided by the manufacturer.

Low power consumption

With a maximum power of approximately 1 W, the Control-Key K20 RF has very low consumption, suitable for continuous operation as the communication interface of the heating installation.

LED status indicator

The module features LED signaling to visually indicate its operating status and assist during connection or diagnostics.

The manufacturer’s documentation includes different LED indications, including:

• Green.
• Yellow.
• Red.
• LED off.

The exact meaning of each sequence or color must be interpreted according to the Control-Key K20 RF manual, as it may correspond to the communication, pairing, or operating status of the module.

Reset function

The K20 RF includes a RESET function to perform the operations specified by Bosch during configuration, commissioning, or device reset.

The reset should be carried out following the sequence indicated in the official instructions to avoid unnecessarily deleting or altering a communication configuration.

IP30 protection rating

The Bosch Control-Key K20 RF has an IP30 protection rating.

This means it is intended to be installed in a protected location compatible with the conditions indicated by Bosch, normally associated with the heat generator or the mounting solution established by the manufacturer.

It is not designed as a standalone unit for direct exposure to water, rain, or outdoor environments without appropriate additional protection.

Operating ambient temperature

The manufacturer’s technical documentation specifies an operating ambient temperature range of:

• Minimum temperature: 0 °C.
• Maximum temperature: 50 °C.

The device must be installed in a location that remains within this range during normal operation.

Very compact format

The K20 RF has reduced dimensions that make it easy to integrate inside compatible boilers:

• Height: 65 mm.
• Width: 65 mm.
• Depth: 15 mm.
• Weight: approximately 38.6 g.

Its compact size makes it possible to add wireless connectivity to the system without adding a bulky device to the heating setup.

More flexible wireless installation

One of the main advantages of the Control-Key K20 RF is simplifying the installation of the room controller.

By replacing the wired communication between the boiler and the compatible controller with a radio frequency link, it can help with:

• Renovations where there is no bus cable between the boiler and the room.
• Installations where creating new wall chases is impractical.
• Upgrades of existing control systems.
• More flexible placement of the room controller.
• Reduced visible wiring.

Accessory for the control system

The K20 RF should be considered a communication accessory. It does not generate heat, does not directly regulate room temperature on its own, and does not replace a thermostat or controller.

Its function is to establish wireless communication between compatible Bosch system components.

It is not a WiFi receiver

The Control-Key K20 RF uses radio frequency to communicate with the compatible controller. It should not be confused with other newer Bosch devices, such as certain Connect-Key units, which include WiFi internet connectivity functions.

Remote connectivity, functions available from mobile apps, and internet access depend on the controller and the complete system configuration, not on the K20 RF alone.

Applications of the Bosch Control-Key K20 RF

This module is mainly intended for:

• Compatible Bosch/Junkers heating systems.
• Bosch Condens boilers with a compatible Control-Key housing.
• Wireless communication with EasyControl CT200.
• Control system upgrades.
• Installations where wiring between boiler and controller is to be avoided.
• Homes with compatible Bosch heating control.

Technical specifications of the Bosch K20 RF 7738113610

• Brand: Bosch / Junkers Bosch.
• Reference: 7738113610.
• Model: Control-Key K20 RF.
• Technical identification: EC-CT.
• Type: receiver module / radio frequency communication.
• Application: wireless communication between boiler and compatible controller.
• Main compatible controller: Bosch EasyControl CT200.
• Communication bus: EMS 2.
• Radio frequency band: 868.3-869.5 MHz.
• Maximum RF power: 10 dBm.
• Power supply: 12-23 V DC.
• Maximum power: 1 W.
• Status indicator: LED.
• Reset function: yes.
• Protection rating: IP30.
• Operating ambient temperature: 0-50 °C.
• Height: 65 mm.
• Width: 65 mm.
• Depth: 15 mm.
• Weight: approximately 38.6 g.
• Barcode: 4062321501754.
• Communication technology: radio frequency.
• Installation: in a compatible boiler housing or according to Bosch-authorized configuration.

Wireless communication for Bosch EasyControl systems

The Bosch Control-Key K20 RF 7738113610 allows a compatible Bosch/Junkers boiler to be integrated into a wireless EasyControl regulation system. Its 868 MHz communication eliminates the need for a bus cable between the generator and the controller in compatible configurations, making renovations and upgrades of existing installations especially easier.

Its compact 65 × 65 × 15 mm size, EMS 2 communication, LED signaling, and maximum consumption of only 1 W allow it to be discreetly integrated into the heating system.

Important: the K20 RF is a communication module and not an independent thermostat. It must be used with a boiler and controller that are expressly compatible. Before purchasing, it is advisable to check the exact reference and version of the heat generator, as not all Bosch/Junkers boilers have the required Control-Key port.