Richmond tankless heater displays error 16; water may be excessively hot before shutdown.

Safety first: Turn OFF power and gas. Hot water over-temperature can cause scalding—warn all occupants not to use hot water until resolved.

• Lower set temperature: Use the control panel to reduce the set temperature to 120°F (49°C) or lower.
• Descale the unit: Perform a full descaling of the heat exchanger to remove mineral buildup that can cause hot spots and poor temperature control.
• Check outlet sensor: Inspect the outlet temperature sensor wiring and replace the sensor if it tests out of range.
• Gas valve evaluation: If water temperature still overshoots, a technician should test the gas valve modulation and replace it or the control board if necessary.