Bosch Water Heater & Boiler Installation

The EA code on a Bosch Greenstar boiler means ‘No Flame Detected’. The boiler tried to ignite but couldn’t. Common causes are a closed gas valve, a frozen or blocked condensate pipe, or a dirty ignition electrode. Check your gas supply and condensate drain first.

EC indicates an ‘Ionization Fault’ or flame failure during operation. It can be caused by improper grounding, a bad flame sensor, or gas pressure fluctuation. This typically requires a technician to check electrical grounding and combustion settings.

If there’s no error code, check the flow rate. Bosch tankless units need a minimum flow (usually 0.5 GPM) to trigger firing. Low-flow faucets may not meet this threshold. Also check that the inlet water filter screen isn’t clogged with debris — this is a common cause of low-flow symptoms.

Bosch recommends annual maintenance: cleaning the heat exchanger, inspecting the burner and electrodes, checking the expansion vessel pressure, and cleaning the condensate trap. Regular service ensures efficiency and catches wear before it becomes failure. Book annual service here.

C6 on a Bosch Greenstar boiler indicates a ‘Fan Speed Fault’ — the fan is not reaching the required RPM. This can be caused by a failing fan motor, debris in the fan housing, or a wiring issue between the fan and the control board. The boiler locks out because proper combustion requires precise air-to-fuel ratios controlled by fan speed. A technician needs to test the fan motor and replace it if faulty.

A7 indicates a ‘DHW (Domestic Hot Water) Temperature Sensor’ fault. The sensor that reads outgoing hot water temperature has failed or is reading out of range. The boiler may still heat the central heating loop but won’t produce domestic hot water reliably. The sensor itself is an inexpensive part — the repair is straightforward for a technician familiar with Bosch Greenstar boilers.