Bosch water heater produces lukewarm water only; cannot reach set temperature

Safety first: Turn OFF power and gas before removing covers. Avoid setting temperatures above safe levels (typically 120°F / 49°C for domestic use).

• Check temperature setting: Verify the set temperature on the control panel or remote. Ensure any child lock or maximum limit settings are not restricting temperature.
• Verify flow vs. capacity: Compare your flow rate (e.g., multiple showers running) to the heater's rated capacity at your incoming water temperature. Reduce simultaneous demand if exceeding capacity.
• Inspect burner: With a professional present, observe the burner through the inspection window. If only part of the burner lights, cleaning or service is required.
• Descale heat exchanger: Scale reduces heat transfer and can cause lukewarm output. Perform a descaling procedure.
• Gas supply check: Have a licensed technician verify gas line sizing and pressure under load.