This display indicates that the return temperature of the boiler is excessive. If accompanied by the red FAULT light and LOCKOUT flashing on the display, the return sensor temperature has exceeded 230oF and a serious safety issue exists. The boiler will not restart until the cause of excessive temperature is repaired by a technician and the boiler is RESET.
If the red FAULT light is not illuminated, then the return tem-perature 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 dis-played, the pump will be on as indicated on the second line.
- Check circulator pump operation.
- Assure that there is adequate flow through the boiler by accessing the status menu and assuring that 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.
