This display indicates that the boiler return temperature is excessive. When accompanied by the red FAULT light and LOCKOUT flashing on the display, this code indicates that the return sensor temperature has exceeded 230ºF 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 red FAULT light is not illuminated and this message is displayed, then the return temperature of the boiler is at or above 210ºF. The message will clear automatically when the temperature drops below 194ºF. During the time that this message or lockout 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 on boiler circulator.
- Troubleshoot thermistor by following steps in F02.
