Boiler shows E08; the domestic hot water (DHW) temperature reading is incorrect or missing.

Safety: Turn off power and close water valves to the indirect tank or DHW circuit if necessary.

• Step 1 – Locate the DHW sensor: On Triangle Tube boilers with an indirect tank, the DHW sensor is usually inserted into a dry well on the tank. On combi models, it may be mounted on the DHW outlet or plate heat exchanger.
• Step 2 – Check connection: Reseat the sensor connector and inspect the cable for damage.
• Step 3 – Confirm insertion: Make sure that the sensor is fully inserted into the well and secured with the clip or screw so it can accurately sense tank temperature.
• Step 4 – Reset: Restore power and reset the boiler. If E08 remains, the sensor is likely defective.
• Replace sensor: Remove the old DHW NTC sensor and install a new Triangle Tube-compatible sensor. No water should leak if it is a dry-well type.
• Technician involvement: If the error persists, the control board or wiring harness may need professional diagnosis.