Bosch 8700i 35/40 Natural Gas Condensing Boiler

The Bosch Condens 8700i W 35/40 CB23 condensing boiler, reference 7738100906, is a wall-mounted combi boiler for natural gas designed to provide heating and domestic hot water with a high level of comfort. It offers a nominal heating output of 34 kW and a nominal heat input of 40.8 kW for DHW, with a specific flow rate of up to 18 liters/min at ΔT 30 K.

Its condensing technology, wide modulation range, color display with touch controls, and connectivity options make it a particularly suitable solution for homes with high heating and hot water demand. The Condens 8700i W also combines a black glass front design with a compact wall-mounted format of 780 x 440 x 365 mm.

Condensing combi boiler for heating and DHW

The Bosch Condens 8700i W 35/40 integrates heating and instantaneous domestic hot water production in a single unit. Its nominal heating output is 34 kW according to the ErP energy label, while the maximum useful output reaches 35.2 kW when operating at low temperature of 40/30 °C.

For domestic hot water production, it has a nominal heat input of 40.8 kW and delivers a specific flow rate of 18 liters/min with a temperature rise of 30 K, providing a high level of comfort in homes with significant DHW demand.

Condensing technology and modulation

The Condens 8700i W uses condensing technology to recover part of the energy contained in the combustion gases and improve system efficiency. Bosch declares a seasonal space heating energy efficiency of 94%.

The burner can modulate its output to adapt to the home’s heat demand. Bosch specifies a modulation ratio of up to 1:8 for this range, reducing the supplied output when maximum capacity is not needed and helping to limit repetitive on/off cycles.

Energy class A for heating and hot water

Reference 7738100906 has an A energy rating for both heating and domestic hot water production. The declared DHW load profile is XL.

The seasonal space heating energy efficiency is 94%, while the water heating energy efficiency reaches 83%. When combined with compatible Bosch modulating control systems, the manufacturer indicates that the system can achieve an A+ rating for heating.

Color display with touch control

The boiler includes the Bosch HMI 700 control unit, equipped with a color display and touch buttons. Its interface provides access to the main operating functions, displays system information, and allows error codes to be viewed in text form.

It also includes circuit pressure indication, a dedicated installer menu, a mechanical pressure gauge located behind the front casing, a pressure sensor, and a semi-automatic filling system.

Connectivity and remote control

The Condens 8700i W range is WiFi-ready and can be combined with compatible Bosch control systems. With the Bosch EasyControl CT200 smart thermostat and the corresponding communication accessories, remote control is possible via the Bosch EasyControl app.

This combination allows heating to be managed from compatible devices and provides access to features such as time programming, daily or weekly schedules, and advanced temperature management.

Black glass design

The Condens 8700i W combi version features a black glass front that provides a modern finish and makes it easy to integrate visually into different areas of the home.

Its dimensions are 780 mm high, 440 mm wide, and 365 mm deep, with an unboxed weight of approximately 50 kg. As a wall-mounted boiler, it helps save space without requiring floor installation.

Designed to simplify installation and maintenance

Bosch has designed the Condens 8700i W to facilitate access to its internal components. Both the front panel and side panels can be removed, allowing access to different boiler elements during installation, inspection, and maintenance tasks.

The unit includes a 12-liter expansion vessel and supports a maximum operating pressure of 2.5 bar in the heating circuit and 10 bar in the domestic hot water circuit.

Low NOx emissions

The Condens 8700i W 35/40 belongs to NOx class 6. The current Bosch energy label specifies nitrogen oxide emissions of 24 mg/kWh, helping to reduce the pollutant emissions associated with boiler operation.

Prepared for natural gas

Reference 7738100906 is sold configured for natural gas. Bosch technical documentation also provides for the possibility of converting certain units in this range to liquefied gas using the procedures and components established by the manufacturer.

Installation, commissioning, and any gas type conversion must be carried out by qualified personnel in accordance with current regulations and Bosch’s official instructions.

Technical features of the Bosch Condens 8700i W 35/40

• Brand: Junkers Bosch.
• Reference: 7738100906.
• Official model: GC8700iW 35/40 CB23.
• Range: Condens 8700i W.
• Type: wall-mounted condensing combi boiler.
• Fuel: natural gas.
• Application: heating and instantaneous domestic hot water.
• Nominal heating output ErP: 34 kW.
• Maximum output at 40/30 °C: 35.2 kW.
• Maximum output at 80/60 °C: 33.6 kW.
• Nominal DHW heat input: 40.8 kW.
• Specific DHW flow rate at ΔT 30 K: 18 liters/min.
• DHW load profile: XL.
• Energy class for heating: A.
• Energy class for DHW: A.
• Seasonal space heating energy efficiency: 94%.
• Water heating energy efficiency: 83%.
• Modulation: up to 1:8.
• NOx class: 6.
• NOx emissions: 24 mg/kWh.
• Expansion vessel: 12 liters.
• Maximum heating circuit pressure: 2.5 bar.
• Maximum DHW circuit pressure: 10 bar.
• Maximum flow temperature: 88 °C.
• ErP sound power level: 53 dB.
• Protection rating: IPX4D.
• Power supply: 230 V, 50 Hz.
• Dimensions: 780 x 440 x 365 mm.
• Unboxed weight: 50 kg.
• Installation: wall-mounted.
• Display: color screen with touch controls.
• Connectivity: ready for connected control via compatible Bosch solutions.

DHW comfort for homes with higher demand

The 40.8 kW output dedicated to hot water and the specific flow rate of 18 liters/min make the Condens 8700i W 35/40 a suitable solution for homes where DHW comfort is a priority. As a combi boiler, hot water is produced instantly without the need to install a separate storage tank.

A high-performance Bosch boiler

The Bosch Condens 8700i W 35/40 combines 34 kW nominal heating output, 40.8 kW for DHW production, condensing technology, and a 94% seasonal efficiency. Its modulating control, color touch interface, and connectivity options complete a unit designed to provide comfort and efficient domestic heating management.

Its compact wall-mounted design, black glass front, and simplified access to internal components make it suitable for both new installations and boiler replacement projects.

Important: installation and commissioning of a gas boiler must be carried out by a qualified professional, following Bosch instructions and the applicable current regulations for gas installations, combustion gas evacuation, and HVAC systems.