F05 indicates the boiler supply temperature is excessive. When accompanied by the red FAULT light and LOCKOUT flashing on the display, this code indicates the supply sensor temperature has exceeded 199oF and a serious safety issue exists. The boiler will not restart until a technician determines and repairs the cause of excessive temperature and pushes RESET on the display. If the FAULT light is not illuminated and this message is displayed, the supply temperature of the boiler is at or above 199ºF. The message will clear automatically when the temperature drops below 194ºF. During the time that this fault is displayed, the pump will be on.
- Check circulator pump operation.
- Ensure adequate flow through the boiler by accessing the status menu and determining there is less than a 50°F rise from the return thermistor to the supply thermistor.
- Check the direction of flow off the boiler circulator.
- Troubleshoot the thermistor by following steps in F02.
