Flue gas sensor over 230°F (110°C).
1. Check that the electrical resistance of the flue gas sensor complies. If the flue gas sensor resistance does not correspond with the correct values, replace it.
2. Check that the efficiency of the boiler is over 86%. if the boiler effi ciency is less than 86% and the CO2 content is correct, the primary heat exchanger has to be replaced and proper water treatment methods employed to prevent mineral build up on the water side.
